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Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 1 due Wednesday September 13 2006 before 1230 PM
Suggested Reading
Refresh your mechanics knowledge by reading from your favorite Mechanics book For example the book by Marion amp Thornton is very helpful Goldstein is a bit too dry for this initial ldquoNewtonian mechanics refresherrdquo
Problems
Problem 11 (20 pts)
A block of mass m1 rests on top of a block of mass m2 The static and kinetic coefficients of friction between the two blocks and the bottom block and the table are micros and microk A fixed force F is applied to the bottom block
m
m 1
2
friction
friction F
Describe the motion and find the accelerations of the two blocks a1 and a2 for all possible values of F from F = 0 rarr infin
Problem 12 (20 pts)
Consider a thin circular hoop of radius R and mass m attached to the wall with a frictionless screw The hoop can swing freely but it cannot slip Parametrize the position of the hoop in terms of the angular displacement from the vertical θ Write the equations of motion in terms of θ and its derivatives Find all solutions in the limit of small amplitude motion of the hoop What is the period of oscillation of the hoop What is the length of a simple mathematical pendulum of length L and mass m with the same period of oscillation Gravitational acceleration is g
Problem 13 (20 pts)
Mass m slides down a frictionless incline as shown in Figure 2 The mass is released at a height h above the bottom of the loop
a What is the magnitude and direction of the velocity and the force on the mass at the bottom of the incline (point A)
b What is the magnitude and direction of the velocity and the force on the mass at point B right before the mass leaves the track
c At what speed does the mass leave the track
d How far away from point A does the block land on the level ground
e Sketch the potential energy of the mass as a function of position U(x)
1
m
R
B 45
h
xA
Problem 14 (20 pts)
A particle moves in a two dimensional orbit defined by
x(t) = A(2αt minus sin αt)
y(t) = A(1 minus cos αt)
a Find the tangential acceleration at and normal acceleration an as a function of time where the tangential and normal components are taken with respect to the velocity
b Determine at what times in the orbit an has a maximum
Problem 15 (20 pts)
A particle of mass m slides down an inclined plane with inclination angle θ under the influence of gravity If the motion is resisted by a force f = kmv2 show that the time required to move a distance d after starting from rest is
coshminus1(ekd)t = radic
kg sin θ
2
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 2 due Wednesday September 20 2006 at 1230 PM
Suggested Reading
Goldstein Sections 11-12 and 21-25
Problems
Problem 21 (20 pts)
Goldstein Problem 6 Chapter 2 Page 64
Problem 22 (20 pts)
Goldstein Problem 7 Chapter 2 Page 65
Problem 23 (20 pts)
Goldstein Problem 10 Chapter 2 Page 65
Problem 24 (20 pts)
Consider a region of space divided by a plane The potential energy of a particle in region 1 is U1 and in region 2 is U2 If a particle of mass m and with speed v1 in region 1 passes from region 1 to region 2 such that its path in region 1 makes an angle θ1 with the normal to the plane of separation and an angle θ2 with the normal to the plane when in region 2 show that
sin θ1 U1 minus U2 = 1 +sin θ2 T1
where T1 = 12 mv12 What is the optical analog of this problem
Problem 25 (20 pts)
A pendulum consists of a mass m suspended by a massless spring with unextended length b and spring constant k Find Lagrangersquos equations of motion
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 3due Wednesday September 27 2006 at 1230 PM
Suggested Reading
Goldstein Chapter 13 14 24 26 27
Problems
Problem 31 (20 pts)
Goldstein Problem 5 Chapter 1 Page 30
Problem 32 (20 pts)
Goldstein Problem 10 Chapter 1 Page 31
Problem 33 (20 pts)
Goldstein Problem 21 Chapter 1 Page 33
Problem 34 (20 pts)
Goldstein Problem 20 Chapter 2 Page 68
Problem 35 (20 pts)
Goldstein Problem 26 Chapter 2 Page 69
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 4due Wednesday October 11 2005 at 1230 PM
Suggested Reading
Goldstein Sections 81 and 82
Problems
Problem 41 (25 pts)
Goldstein Problem 1 Chapter 8 Page 362
Problem 42 (25 pts)
Goldstein Problem 13 Chapter 8 Page 363
Problem 43 (25 pts)
Goldstein Problem 19 Chapter 8 Page 364
Problem 44 (25 pts)
Goldstein Problem 21 Chapter 8 Page 365
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 5due Monday October 18 2006 at 1230 PM
Suggested Reading
Goldstein ChapterSection Canonical Transformations 91-939697
Problems
Problem 51 (20 pts)
Goldstein Chapter 9 Problem 4 page 422
Problem 52 (20 pts)
Goldstein Chapter 9 Problem 9 page 423
Problem 53 (20 pts)
Goldstein Chapter 9 Problem 21 page 424
Problem 54 (20 pts)
Goldstein Chapter 9 Problem 26 page 426
Problem 55 (20 pts)
Goldstein Chapter 9 Problem 31 page 427
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 6due Wednesday October 25 2006 at 1230 PM
Suggested Reading
Goldstein Kepler Problem 31-33
Problems
Problem 61 (25 pts)
Goldstein Chapter 3 Problem 11 page 128
Problem 62 (25 pts)
Goldstein Chapter 3 Problem 18 page 129
Problem 63 (25 pts)
Goldstein Chapter 3 Exercise 19 page 129
Problem 64 (25 pts)
Goldstein Chapter 3 Exercise 21 page 130
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 7due Monday November 6 2006 at 1230 PM (Note unusual date)
Suggested Reading
Goldstein Collisions 310-311 lecture material Marion and Thornton 96-910 (Goldstein doesnrsquot contain a lot about scattering)
Problems
Problem 71 (20 pts)
Marion amp Thornton 9-26
Problem 72 (20 pts)
Marion amp Thornton 9-33
Problem 73 (20 pts)
Marion amp Thornton 9-45
Problem 74 (20 pts)
Marion amp Thornton 9-48
Problem 75 (20 pts)
Marion amp Thornton 9-50
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 8due Monday November 8 2006 at 1230 PM
Suggested Reading
Lecture Material Goldstein Sections 49 410 53 and 54 Also Chapter 10 Marion and Thronton
Problems
Problem 81 (25 pts)
Goldstein Exercise 22 page 183
Problem 82 (25 pts)
Marion and Thornton 10-12
Problem 83 (25 pts)
Marion and Thornton 10-15
Problem 84 (25 pts)
Goldstein Exercise 17 page 235
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 9due Wednesday November 29 2006 at 1230 PM
Suggested Reading
Goldstein Chapter 5
Problems
Problem 91 (25 pts)
Goldstein Derivation 6 page 233 Ignore the last sentence of question c) (Poinsot construction)
Problem 92 (25 pts)
Goldstein Exercise 18 page 235
Problem 93 (25 pts)
Goldstein Exercise 20 page 236
Problem 94 (25 pts)
Goldstein Exercise 29 page 237
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 10due Wednesday December 6 2006 at 1230 PM
Suggested Reading
Goldstein Sections 15 85 and Chapter 13
Problems
Problem 101 (25 pts)
Goldstein Exercise 1 page 598
Problem 102 (25 pts)
Goldstein Exercise 3 page 599
Problem 103 (25 pts)
Goldstein Exercise 4 page 599
Problem 104 (25 pts)
Goldstein Exercise 12 page 600
1
Massachusetts Institute of Technology Department of Physics
Course 809 Classical Mechanics Term Fall 2006
Quiz 1 October 4 2006
Instructions
bull Do not start until you are told to do so
bull Solve all problems
bull Put your name on the covers of all notebooks you are using
bull Show all work neatly in the blue book label the problem you are working on
bull Mark the final answers
bull Books and notes are not to be used Calculators are unnecessary
2
Useful Formulae
Newton and Basic Kinematics
F = p = ma for v c t=t
v = v0 +
dta t=0
t=t =t
r = r0 + v0t +
dt t
dtF (t)m t=0 t =0
Lagrangian and Hamiltonian
L(q q) = T minus U H(p q) = T + U = pq minus L
Euler-Lagrange (without and with constraints)
partL d partL partL d partL partgaminus = 0 minus + λa = 0 partx dt partx partx dt partx partxa
Polar Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Cylindrical Coordinates
x = r cos φ y = r sin φ z = z
Possibly useful integrals
dx dx = arctan(x) = arctanh(x)
1 + x2 1 minus x2
3
Problem 1 Variable Length Pendulum (35 points)
Consider a simple pendulum consisting of mass m attached to a string of length L After the pendulum is set into motion (at t = 0) the length of the string is lenghtened at a constant rate
dL = α = constant
dt The suspension point remains fixed
a) How many degrees of freedom does the system have
b) Write the Lagrangian for the pendulum Calculate partL is it equal to zero partt
c) Write the equations of motion for the pendulum do not solve Show that the equations of motion become the equations of the fixed length pendulum for α = 0
d) Write the Hamiltonian for the system
e) Calculate the total mechanical energy of the system Compare to the Hamiltoshynian
f) The energy of the system is not conserved What is the rate of change Give physical interpretation of the sources and magnitude of power flowing in or out of the system
Problem 2 Particle on a rotating wire (35 points)
A particle of mass m is constrained to move along a straight frictionless wire The wire is rotating in a vertical plane at a constant angular velocity Ω as shown in the Figure 1 The system is in the gravitational field with gravitational acceleration g pointing downwards At t = 0 the mass was stationary with respect to the wire and it was at a distance R0 from the axis of rotation
a) Write the Lagrangian for a free mass constrained to the vertical plane in gravishytational field using polar coordinate system
b) Write explicitly the constraint equations that force the mass to remain on the rotating wire
c) Write equations of motion for all the coordinates introducing Lagrange Multiplishyers
4
m
g
R0 Ω
Figure 1 Particle on a rotating wire
d) Obtain the expressions for the forces of constraints Give the physical interpreshytation of these forces
e) For sufficiently large Ω the mass will be moving away from the rotation axis for all wire positions What is the minimum value of the angular velocity such that this is guaranteed
Problem 3 Double Pendulum (30 points)
Consider a system consisting of two masses m1 and m2 and connected with massless rigid rods of length L1 and L2 (see Figure 2) As the pendulum moves both masses remain in the vertical plane
L1
g
m 1
L 2
m 2
Figure 2 Double Pendulum
a) How many degrees of freedom does the system have
b) Write the Lagrangian for the system
c) Write equations of motion for the system Do not solve
Massachusetts Institute of Technology Department of Physics
Course 809 Classical Mechanics Term Fall 2006
Quiz 2 November 15 2006
Instructions
bull Do not start until you are told to do so
bull Solve all problems
bull Put your name on the covers of all notebooks you are using
bull Show all work neatly in the white book label the problem you are working on
bull Mark the final answers
bull Books and notes are not to be used You may use your calculator
2
Useful Formulae
Newton and Basic Kinematics
F = p = ma for v c t=t v = v0 + dtprimea
t=0 t=t t=t
r = r0 + v0t + dtprime dtprimeprimeF (tprimeprime)m t=0 t =0
Gravitational Law
F = minus Gm1m2
r122r12
Lagrangian and Hamiltonian
partqL(q q) = T minus U H(p q) = T + U = p minus L
partt
Hamilton Equation of Motion
partH partH = minusp = q
partq partp
Generating function
partF (Q q) partF (Q q) = p = minusP
partq partQ
Poisson Brackets
partg partf partg partf [g f ] = minus
partq partp partp partq
Euler-Lagrange (without and with constraints)
partL d partL partL d partL partgminus = 0 minus + λ = 0 partx dt partx partx dt partx partx
Polar Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Orbit Equation
micro 1 u primeprime + u = minus F (u) with u =
2u2 r
ε =
3
Effective Potential
2
V (r) = U(r) + 2micror2
Keplerian Orbits
k α U(r) = minus = ε cos θ + 1
r r
α = 2
ε = 1 +2E2
τ 2 =4π2micro
a 3
microk microk2 k α α
rmin = a(1 minus ε) = rmax = a(1 + ε) =1 + ε 1 minus ε
Spherical Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Inelastic Scattering (coefficient of restitution)
|v2 minus v1||u2 minus u1|
Scattering
dσ dσ b db σ(θ) = = =
dΩ dφ sin θdθ sin θ dθ sin θ π θ
tan ψ = ζ = minus cos θ + (m1m2) 2 2
Vector in fixed frame expressed in terms of vector in rotating frame and rotation velocity
dX dX( )inertial = ( )rotating + (ω times X )dt dt
Acceleration in accelerated and rotating frame
a = g minus V minus (ω times r) minus 2(ω times v) minus (ω times (ω times r))
Useful Trigonometrical Formulas
sin(A + B) = sin A cos B + cos A sin B
cos(A + B) = cos A cos B minus sin A sin B
4
Problem 1 Canonical Transformation (35 points)
Consider a harmonic oscillator with Hamiltonian
p2 mω2q2
H = + 2m 2
Introduce transformation of variables from q(t) and p(t) to Q(t) = q(t + τ) and P (t) = p(t + τ) where τ is constant The goal of this problem is to find generating function F (Q q) of this canonical transformation of variables
a) Solve Hamilton equations of motion and find q(t) and p(t) for arbitrary initial conditions
b) Express P and p as functions of only q Q m ω and τ You may want first to express Q and P as the functions of q and p and then rearrange equations Note that there should be no time dependence in these expressions
c) Integrate p as a function of q to obtain q-dependence of F Remember to include the undetermined integrating constant(q) C(Q)
d) Use equation for P (Q q) to find C(Q) and determine F (Q q)
e) Verify that F (Q q) is the correct generating function
5
Problem 2 Scattering from a rotationally symmetric surface (30 points)
Consider small particles moving with velocity parallel to the z-axis Particles are scattering from a perfectly elastic and frictionless surface The surface is rotationally symmetric about the z-axis and the shape of the surface is ρ(z) = z3 for z gt 0 We want to find differential scattering cross section σ(θ)
a) Find the relationship between the scattering angle θ and the impact parameter Note that the surface at the impact point can be considered as a perfectly elastic wall tangential to the curve at that point
b) Extract b(θ) and determine the differential cross section
c) Make a sketch of the scattering angle at some representative point ρ(z) for the case of the surface that is frictionless but totally inelastic
d) Make a sketch of the scattering angle at some representative point ρ(z) for the case of surface that is elastic but it has very high friction
6
Problem 3 Motion in rotating frame (35 points)
Consider a cannon located at geographical lattitude of exactly 45o North Cannon can fire identical projectiles in East North West and South directions All projectiles have identical initial speed of v0 = 200 ms and the cannon always points up at exactly 45o to the horizontal In your calculations of the projectile trajectory you can ignore the curvature of the Earth Assume that there is no air resistance
Assume that the radius of the Earth is R = 6 middot106 m and that the angular velocity of Earthrsquos rotation is Ω = 7 middot 10minus5 sminus1 Gravitational acceleration is g = 10 ms2 Do your calculations in the coordinate system where the z-axis is vertical pointing up with 0 at the center of the Earth the x-axis points North and the y-axis points West
a) Assume that the Earth is not rotating Obtain the algebraic formulas and the numericals value for the total range in meters maximum height above the ground in meters and the projectile flight time in seconds
b) Assume now that the Earth is rotating with its usual Ω Write down an expresshy
sion for acceleration ai = (ax ay az) in terms of components of r = (x y z) and Ω v = (x y˙ z) Ignore very small terms proportional to Ω2x Ω2y and replace radicz with R Keep all variables in algebraic form but replace sin 45o and cos 45o with 1 2
Note the following sections can be quite time consuming Start them only after you have finalized the other problems and sections in this quiz
c) The gun is being shot in the four geographical directions ENW S Write down the expressions for acceleration individually for each direction In each case remove the very small terms and find cancellations of terms of roughly equal size Justify your choices Note that some numerical cancellations are possible since the speed of the projectile happens to be very close to the linear speed of the Earthrsquos surface at that lattitude
d) Based on the magnitudes and signs of the terms of a obtained in c) estimate the effect of the earthrsquos rotation on the position of the impact parameter of the projectile for each of the four cases Mark the location of the new impact point as compared to no-rotation impact point (as obtained in a)) on graphs similar to Figure 1 The center of the graph corresponds to the no-rotation impact position Do not do the precise calculations try only to estimate the direction and relative magnitude of the deviation All four graphs should be oriented with North at the top and East to the right
7
x
yNorth
East
West
South
Figure 1 Impact Point Graph
m
R
B 45
h
xA
Problem 14 (20 pts)
A particle moves in a two dimensional orbit defined by
x(t) = A(2αt minus sin αt)
y(t) = A(1 minus cos αt)
a Find the tangential acceleration at and normal acceleration an as a function of time where the tangential and normal components are taken with respect to the velocity
b Determine at what times in the orbit an has a maximum
Problem 15 (20 pts)
A particle of mass m slides down an inclined plane with inclination angle θ under the influence of gravity If the motion is resisted by a force f = kmv2 show that the time required to move a distance d after starting from rest is
coshminus1(ekd)t = radic
kg sin θ
2
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 2 due Wednesday September 20 2006 at 1230 PM
Suggested Reading
Goldstein Sections 11-12 and 21-25
Problems
Problem 21 (20 pts)
Goldstein Problem 6 Chapter 2 Page 64
Problem 22 (20 pts)
Goldstein Problem 7 Chapter 2 Page 65
Problem 23 (20 pts)
Goldstein Problem 10 Chapter 2 Page 65
Problem 24 (20 pts)
Consider a region of space divided by a plane The potential energy of a particle in region 1 is U1 and in region 2 is U2 If a particle of mass m and with speed v1 in region 1 passes from region 1 to region 2 such that its path in region 1 makes an angle θ1 with the normal to the plane of separation and an angle θ2 with the normal to the plane when in region 2 show that
sin θ1 U1 minus U2 = 1 +sin θ2 T1
where T1 = 12 mv12 What is the optical analog of this problem
Problem 25 (20 pts)
A pendulum consists of a mass m suspended by a massless spring with unextended length b and spring constant k Find Lagrangersquos equations of motion
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 3due Wednesday September 27 2006 at 1230 PM
Suggested Reading
Goldstein Chapter 13 14 24 26 27
Problems
Problem 31 (20 pts)
Goldstein Problem 5 Chapter 1 Page 30
Problem 32 (20 pts)
Goldstein Problem 10 Chapter 1 Page 31
Problem 33 (20 pts)
Goldstein Problem 21 Chapter 1 Page 33
Problem 34 (20 pts)
Goldstein Problem 20 Chapter 2 Page 68
Problem 35 (20 pts)
Goldstein Problem 26 Chapter 2 Page 69
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 4due Wednesday October 11 2005 at 1230 PM
Suggested Reading
Goldstein Sections 81 and 82
Problems
Problem 41 (25 pts)
Goldstein Problem 1 Chapter 8 Page 362
Problem 42 (25 pts)
Goldstein Problem 13 Chapter 8 Page 363
Problem 43 (25 pts)
Goldstein Problem 19 Chapter 8 Page 364
Problem 44 (25 pts)
Goldstein Problem 21 Chapter 8 Page 365
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 5due Monday October 18 2006 at 1230 PM
Suggested Reading
Goldstein ChapterSection Canonical Transformations 91-939697
Problems
Problem 51 (20 pts)
Goldstein Chapter 9 Problem 4 page 422
Problem 52 (20 pts)
Goldstein Chapter 9 Problem 9 page 423
Problem 53 (20 pts)
Goldstein Chapter 9 Problem 21 page 424
Problem 54 (20 pts)
Goldstein Chapter 9 Problem 26 page 426
Problem 55 (20 pts)
Goldstein Chapter 9 Problem 31 page 427
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 6due Wednesday October 25 2006 at 1230 PM
Suggested Reading
Goldstein Kepler Problem 31-33
Problems
Problem 61 (25 pts)
Goldstein Chapter 3 Problem 11 page 128
Problem 62 (25 pts)
Goldstein Chapter 3 Problem 18 page 129
Problem 63 (25 pts)
Goldstein Chapter 3 Exercise 19 page 129
Problem 64 (25 pts)
Goldstein Chapter 3 Exercise 21 page 130
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 7due Monday November 6 2006 at 1230 PM (Note unusual date)
Suggested Reading
Goldstein Collisions 310-311 lecture material Marion and Thornton 96-910 (Goldstein doesnrsquot contain a lot about scattering)
Problems
Problem 71 (20 pts)
Marion amp Thornton 9-26
Problem 72 (20 pts)
Marion amp Thornton 9-33
Problem 73 (20 pts)
Marion amp Thornton 9-45
Problem 74 (20 pts)
Marion amp Thornton 9-48
Problem 75 (20 pts)
Marion amp Thornton 9-50
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 8due Monday November 8 2006 at 1230 PM
Suggested Reading
Lecture Material Goldstein Sections 49 410 53 and 54 Also Chapter 10 Marion and Thronton
Problems
Problem 81 (25 pts)
Goldstein Exercise 22 page 183
Problem 82 (25 pts)
Marion and Thornton 10-12
Problem 83 (25 pts)
Marion and Thornton 10-15
Problem 84 (25 pts)
Goldstein Exercise 17 page 235
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 9due Wednesday November 29 2006 at 1230 PM
Suggested Reading
Goldstein Chapter 5
Problems
Problem 91 (25 pts)
Goldstein Derivation 6 page 233 Ignore the last sentence of question c) (Poinsot construction)
Problem 92 (25 pts)
Goldstein Exercise 18 page 235
Problem 93 (25 pts)
Goldstein Exercise 20 page 236
Problem 94 (25 pts)
Goldstein Exercise 29 page 237
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 10due Wednesday December 6 2006 at 1230 PM
Suggested Reading
Goldstein Sections 15 85 and Chapter 13
Problems
Problem 101 (25 pts)
Goldstein Exercise 1 page 598
Problem 102 (25 pts)
Goldstein Exercise 3 page 599
Problem 103 (25 pts)
Goldstein Exercise 4 page 599
Problem 104 (25 pts)
Goldstein Exercise 12 page 600
1
Massachusetts Institute of Technology Department of Physics
Course 809 Classical Mechanics Term Fall 2006
Quiz 1 October 4 2006
Instructions
bull Do not start until you are told to do so
bull Solve all problems
bull Put your name on the covers of all notebooks you are using
bull Show all work neatly in the blue book label the problem you are working on
bull Mark the final answers
bull Books and notes are not to be used Calculators are unnecessary
2
Useful Formulae
Newton and Basic Kinematics
F = p = ma for v c t=t
v = v0 +
dta t=0
t=t =t
r = r0 + v0t +
dt t
dtF (t)m t=0 t =0
Lagrangian and Hamiltonian
L(q q) = T minus U H(p q) = T + U = pq minus L
Euler-Lagrange (without and with constraints)
partL d partL partL d partL partgaminus = 0 minus + λa = 0 partx dt partx partx dt partx partxa
Polar Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Cylindrical Coordinates
x = r cos φ y = r sin φ z = z
Possibly useful integrals
dx dx = arctan(x) = arctanh(x)
1 + x2 1 minus x2
3
Problem 1 Variable Length Pendulum (35 points)
Consider a simple pendulum consisting of mass m attached to a string of length L After the pendulum is set into motion (at t = 0) the length of the string is lenghtened at a constant rate
dL = α = constant
dt The suspension point remains fixed
a) How many degrees of freedom does the system have
b) Write the Lagrangian for the pendulum Calculate partL is it equal to zero partt
c) Write the equations of motion for the pendulum do not solve Show that the equations of motion become the equations of the fixed length pendulum for α = 0
d) Write the Hamiltonian for the system
e) Calculate the total mechanical energy of the system Compare to the Hamiltoshynian
f) The energy of the system is not conserved What is the rate of change Give physical interpretation of the sources and magnitude of power flowing in or out of the system
Problem 2 Particle on a rotating wire (35 points)
A particle of mass m is constrained to move along a straight frictionless wire The wire is rotating in a vertical plane at a constant angular velocity Ω as shown in the Figure 1 The system is in the gravitational field with gravitational acceleration g pointing downwards At t = 0 the mass was stationary with respect to the wire and it was at a distance R0 from the axis of rotation
a) Write the Lagrangian for a free mass constrained to the vertical plane in gravishytational field using polar coordinate system
b) Write explicitly the constraint equations that force the mass to remain on the rotating wire
c) Write equations of motion for all the coordinates introducing Lagrange Multiplishyers
4
m
g
R0 Ω
Figure 1 Particle on a rotating wire
d) Obtain the expressions for the forces of constraints Give the physical interpreshytation of these forces
e) For sufficiently large Ω the mass will be moving away from the rotation axis for all wire positions What is the minimum value of the angular velocity such that this is guaranteed
Problem 3 Double Pendulum (30 points)
Consider a system consisting of two masses m1 and m2 and connected with massless rigid rods of length L1 and L2 (see Figure 2) As the pendulum moves both masses remain in the vertical plane
L1
g
m 1
L 2
m 2
Figure 2 Double Pendulum
a) How many degrees of freedom does the system have
b) Write the Lagrangian for the system
c) Write equations of motion for the system Do not solve
Massachusetts Institute of Technology Department of Physics
Course 809 Classical Mechanics Term Fall 2006
Quiz 2 November 15 2006
Instructions
bull Do not start until you are told to do so
bull Solve all problems
bull Put your name on the covers of all notebooks you are using
bull Show all work neatly in the white book label the problem you are working on
bull Mark the final answers
bull Books and notes are not to be used You may use your calculator
2
Useful Formulae
Newton and Basic Kinematics
F = p = ma for v c t=t v = v0 + dtprimea
t=0 t=t t=t
r = r0 + v0t + dtprime dtprimeprimeF (tprimeprime)m t=0 t =0
Gravitational Law
F = minus Gm1m2
r122r12
Lagrangian and Hamiltonian
partqL(q q) = T minus U H(p q) = T + U = p minus L
partt
Hamilton Equation of Motion
partH partH = minusp = q
partq partp
Generating function
partF (Q q) partF (Q q) = p = minusP
partq partQ
Poisson Brackets
partg partf partg partf [g f ] = minus
partq partp partp partq
Euler-Lagrange (without and with constraints)
partL d partL partL d partL partgminus = 0 minus + λ = 0 partx dt partx partx dt partx partx
Polar Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Orbit Equation
micro 1 u primeprime + u = minus F (u) with u =
2u2 r
ε =
3
Effective Potential
2
V (r) = U(r) + 2micror2
Keplerian Orbits
k α U(r) = minus = ε cos θ + 1
r r
α = 2
ε = 1 +2E2
τ 2 =4π2micro
a 3
microk microk2 k α α
rmin = a(1 minus ε) = rmax = a(1 + ε) =1 + ε 1 minus ε
Spherical Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Inelastic Scattering (coefficient of restitution)
|v2 minus v1||u2 minus u1|
Scattering
dσ dσ b db σ(θ) = = =
dΩ dφ sin θdθ sin θ dθ sin θ π θ
tan ψ = ζ = minus cos θ + (m1m2) 2 2
Vector in fixed frame expressed in terms of vector in rotating frame and rotation velocity
dX dX( )inertial = ( )rotating + (ω times X )dt dt
Acceleration in accelerated and rotating frame
a = g minus V minus (ω times r) minus 2(ω times v) minus (ω times (ω times r))
Useful Trigonometrical Formulas
sin(A + B) = sin A cos B + cos A sin B
cos(A + B) = cos A cos B minus sin A sin B
4
Problem 1 Canonical Transformation (35 points)
Consider a harmonic oscillator with Hamiltonian
p2 mω2q2
H = + 2m 2
Introduce transformation of variables from q(t) and p(t) to Q(t) = q(t + τ) and P (t) = p(t + τ) where τ is constant The goal of this problem is to find generating function F (Q q) of this canonical transformation of variables
a) Solve Hamilton equations of motion and find q(t) and p(t) for arbitrary initial conditions
b) Express P and p as functions of only q Q m ω and τ You may want first to express Q and P as the functions of q and p and then rearrange equations Note that there should be no time dependence in these expressions
c) Integrate p as a function of q to obtain q-dependence of F Remember to include the undetermined integrating constant(q) C(Q)
d) Use equation for P (Q q) to find C(Q) and determine F (Q q)
e) Verify that F (Q q) is the correct generating function
5
Problem 2 Scattering from a rotationally symmetric surface (30 points)
Consider small particles moving with velocity parallel to the z-axis Particles are scattering from a perfectly elastic and frictionless surface The surface is rotationally symmetric about the z-axis and the shape of the surface is ρ(z) = z3 for z gt 0 We want to find differential scattering cross section σ(θ)
a) Find the relationship between the scattering angle θ and the impact parameter Note that the surface at the impact point can be considered as a perfectly elastic wall tangential to the curve at that point
b) Extract b(θ) and determine the differential cross section
c) Make a sketch of the scattering angle at some representative point ρ(z) for the case of the surface that is frictionless but totally inelastic
d) Make a sketch of the scattering angle at some representative point ρ(z) for the case of surface that is elastic but it has very high friction
6
Problem 3 Motion in rotating frame (35 points)
Consider a cannon located at geographical lattitude of exactly 45o North Cannon can fire identical projectiles in East North West and South directions All projectiles have identical initial speed of v0 = 200 ms and the cannon always points up at exactly 45o to the horizontal In your calculations of the projectile trajectory you can ignore the curvature of the Earth Assume that there is no air resistance
Assume that the radius of the Earth is R = 6 middot106 m and that the angular velocity of Earthrsquos rotation is Ω = 7 middot 10minus5 sminus1 Gravitational acceleration is g = 10 ms2 Do your calculations in the coordinate system where the z-axis is vertical pointing up with 0 at the center of the Earth the x-axis points North and the y-axis points West
a) Assume that the Earth is not rotating Obtain the algebraic formulas and the numericals value for the total range in meters maximum height above the ground in meters and the projectile flight time in seconds
b) Assume now that the Earth is rotating with its usual Ω Write down an expresshy
sion for acceleration ai = (ax ay az) in terms of components of r = (x y z) and Ω v = (x y˙ z) Ignore very small terms proportional to Ω2x Ω2y and replace radicz with R Keep all variables in algebraic form but replace sin 45o and cos 45o with 1 2
Note the following sections can be quite time consuming Start them only after you have finalized the other problems and sections in this quiz
c) The gun is being shot in the four geographical directions ENW S Write down the expressions for acceleration individually for each direction In each case remove the very small terms and find cancellations of terms of roughly equal size Justify your choices Note that some numerical cancellations are possible since the speed of the projectile happens to be very close to the linear speed of the Earthrsquos surface at that lattitude
d) Based on the magnitudes and signs of the terms of a obtained in c) estimate the effect of the earthrsquos rotation on the position of the impact parameter of the projectile for each of the four cases Mark the location of the new impact point as compared to no-rotation impact point (as obtained in a)) on graphs similar to Figure 1 The center of the graph corresponds to the no-rotation impact position Do not do the precise calculations try only to estimate the direction and relative magnitude of the deviation All four graphs should be oriented with North at the top and East to the right
7
x
yNorth
East
West
South
Figure 1 Impact Point Graph
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 2 due Wednesday September 20 2006 at 1230 PM
Suggested Reading
Goldstein Sections 11-12 and 21-25
Problems
Problem 21 (20 pts)
Goldstein Problem 6 Chapter 2 Page 64
Problem 22 (20 pts)
Goldstein Problem 7 Chapter 2 Page 65
Problem 23 (20 pts)
Goldstein Problem 10 Chapter 2 Page 65
Problem 24 (20 pts)
Consider a region of space divided by a plane The potential energy of a particle in region 1 is U1 and in region 2 is U2 If a particle of mass m and with speed v1 in region 1 passes from region 1 to region 2 such that its path in region 1 makes an angle θ1 with the normal to the plane of separation and an angle θ2 with the normal to the plane when in region 2 show that
sin θ1 U1 minus U2 = 1 +sin θ2 T1
where T1 = 12 mv12 What is the optical analog of this problem
Problem 25 (20 pts)
A pendulum consists of a mass m suspended by a massless spring with unextended length b and spring constant k Find Lagrangersquos equations of motion
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 3due Wednesday September 27 2006 at 1230 PM
Suggested Reading
Goldstein Chapter 13 14 24 26 27
Problems
Problem 31 (20 pts)
Goldstein Problem 5 Chapter 1 Page 30
Problem 32 (20 pts)
Goldstein Problem 10 Chapter 1 Page 31
Problem 33 (20 pts)
Goldstein Problem 21 Chapter 1 Page 33
Problem 34 (20 pts)
Goldstein Problem 20 Chapter 2 Page 68
Problem 35 (20 pts)
Goldstein Problem 26 Chapter 2 Page 69
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 4due Wednesday October 11 2005 at 1230 PM
Suggested Reading
Goldstein Sections 81 and 82
Problems
Problem 41 (25 pts)
Goldstein Problem 1 Chapter 8 Page 362
Problem 42 (25 pts)
Goldstein Problem 13 Chapter 8 Page 363
Problem 43 (25 pts)
Goldstein Problem 19 Chapter 8 Page 364
Problem 44 (25 pts)
Goldstein Problem 21 Chapter 8 Page 365
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 5due Monday October 18 2006 at 1230 PM
Suggested Reading
Goldstein ChapterSection Canonical Transformations 91-939697
Problems
Problem 51 (20 pts)
Goldstein Chapter 9 Problem 4 page 422
Problem 52 (20 pts)
Goldstein Chapter 9 Problem 9 page 423
Problem 53 (20 pts)
Goldstein Chapter 9 Problem 21 page 424
Problem 54 (20 pts)
Goldstein Chapter 9 Problem 26 page 426
Problem 55 (20 pts)
Goldstein Chapter 9 Problem 31 page 427
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 6due Wednesday October 25 2006 at 1230 PM
Suggested Reading
Goldstein Kepler Problem 31-33
Problems
Problem 61 (25 pts)
Goldstein Chapter 3 Problem 11 page 128
Problem 62 (25 pts)
Goldstein Chapter 3 Problem 18 page 129
Problem 63 (25 pts)
Goldstein Chapter 3 Exercise 19 page 129
Problem 64 (25 pts)
Goldstein Chapter 3 Exercise 21 page 130
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 7due Monday November 6 2006 at 1230 PM (Note unusual date)
Suggested Reading
Goldstein Collisions 310-311 lecture material Marion and Thornton 96-910 (Goldstein doesnrsquot contain a lot about scattering)
Problems
Problem 71 (20 pts)
Marion amp Thornton 9-26
Problem 72 (20 pts)
Marion amp Thornton 9-33
Problem 73 (20 pts)
Marion amp Thornton 9-45
Problem 74 (20 pts)
Marion amp Thornton 9-48
Problem 75 (20 pts)
Marion amp Thornton 9-50
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 8due Monday November 8 2006 at 1230 PM
Suggested Reading
Lecture Material Goldstein Sections 49 410 53 and 54 Also Chapter 10 Marion and Thronton
Problems
Problem 81 (25 pts)
Goldstein Exercise 22 page 183
Problem 82 (25 pts)
Marion and Thornton 10-12
Problem 83 (25 pts)
Marion and Thornton 10-15
Problem 84 (25 pts)
Goldstein Exercise 17 page 235
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 9due Wednesday November 29 2006 at 1230 PM
Suggested Reading
Goldstein Chapter 5
Problems
Problem 91 (25 pts)
Goldstein Derivation 6 page 233 Ignore the last sentence of question c) (Poinsot construction)
Problem 92 (25 pts)
Goldstein Exercise 18 page 235
Problem 93 (25 pts)
Goldstein Exercise 20 page 236
Problem 94 (25 pts)
Goldstein Exercise 29 page 237
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 10due Wednesday December 6 2006 at 1230 PM
Suggested Reading
Goldstein Sections 15 85 and Chapter 13
Problems
Problem 101 (25 pts)
Goldstein Exercise 1 page 598
Problem 102 (25 pts)
Goldstein Exercise 3 page 599
Problem 103 (25 pts)
Goldstein Exercise 4 page 599
Problem 104 (25 pts)
Goldstein Exercise 12 page 600
1
Massachusetts Institute of Technology Department of Physics
Course 809 Classical Mechanics Term Fall 2006
Quiz 1 October 4 2006
Instructions
bull Do not start until you are told to do so
bull Solve all problems
bull Put your name on the covers of all notebooks you are using
bull Show all work neatly in the blue book label the problem you are working on
bull Mark the final answers
bull Books and notes are not to be used Calculators are unnecessary
2
Useful Formulae
Newton and Basic Kinematics
F = p = ma for v c t=t
v = v0 +
dta t=0
t=t =t
r = r0 + v0t +
dt t
dtF (t)m t=0 t =0
Lagrangian and Hamiltonian
L(q q) = T minus U H(p q) = T + U = pq minus L
Euler-Lagrange (without and with constraints)
partL d partL partL d partL partgaminus = 0 minus + λa = 0 partx dt partx partx dt partx partxa
Polar Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Cylindrical Coordinates
x = r cos φ y = r sin φ z = z
Possibly useful integrals
dx dx = arctan(x) = arctanh(x)
1 + x2 1 minus x2
3
Problem 1 Variable Length Pendulum (35 points)
Consider a simple pendulum consisting of mass m attached to a string of length L After the pendulum is set into motion (at t = 0) the length of the string is lenghtened at a constant rate
dL = α = constant
dt The suspension point remains fixed
a) How many degrees of freedom does the system have
b) Write the Lagrangian for the pendulum Calculate partL is it equal to zero partt
c) Write the equations of motion for the pendulum do not solve Show that the equations of motion become the equations of the fixed length pendulum for α = 0
d) Write the Hamiltonian for the system
e) Calculate the total mechanical energy of the system Compare to the Hamiltoshynian
f) The energy of the system is not conserved What is the rate of change Give physical interpretation of the sources and magnitude of power flowing in or out of the system
Problem 2 Particle on a rotating wire (35 points)
A particle of mass m is constrained to move along a straight frictionless wire The wire is rotating in a vertical plane at a constant angular velocity Ω as shown in the Figure 1 The system is in the gravitational field with gravitational acceleration g pointing downwards At t = 0 the mass was stationary with respect to the wire and it was at a distance R0 from the axis of rotation
a) Write the Lagrangian for a free mass constrained to the vertical plane in gravishytational field using polar coordinate system
b) Write explicitly the constraint equations that force the mass to remain on the rotating wire
c) Write equations of motion for all the coordinates introducing Lagrange Multiplishyers
4
m
g
R0 Ω
Figure 1 Particle on a rotating wire
d) Obtain the expressions for the forces of constraints Give the physical interpreshytation of these forces
e) For sufficiently large Ω the mass will be moving away from the rotation axis for all wire positions What is the minimum value of the angular velocity such that this is guaranteed
Problem 3 Double Pendulum (30 points)
Consider a system consisting of two masses m1 and m2 and connected with massless rigid rods of length L1 and L2 (see Figure 2) As the pendulum moves both masses remain in the vertical plane
L1
g
m 1
L 2
m 2
Figure 2 Double Pendulum
a) How many degrees of freedom does the system have
b) Write the Lagrangian for the system
c) Write equations of motion for the system Do not solve
Massachusetts Institute of Technology Department of Physics
Course 809 Classical Mechanics Term Fall 2006
Quiz 2 November 15 2006
Instructions
bull Do not start until you are told to do so
bull Solve all problems
bull Put your name on the covers of all notebooks you are using
bull Show all work neatly in the white book label the problem you are working on
bull Mark the final answers
bull Books and notes are not to be used You may use your calculator
2
Useful Formulae
Newton and Basic Kinematics
F = p = ma for v c t=t v = v0 + dtprimea
t=0 t=t t=t
r = r0 + v0t + dtprime dtprimeprimeF (tprimeprime)m t=0 t =0
Gravitational Law
F = minus Gm1m2
r122r12
Lagrangian and Hamiltonian
partqL(q q) = T minus U H(p q) = T + U = p minus L
partt
Hamilton Equation of Motion
partH partH = minusp = q
partq partp
Generating function
partF (Q q) partF (Q q) = p = minusP
partq partQ
Poisson Brackets
partg partf partg partf [g f ] = minus
partq partp partp partq
Euler-Lagrange (without and with constraints)
partL d partL partL d partL partgminus = 0 minus + λ = 0 partx dt partx partx dt partx partx
Polar Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Orbit Equation
micro 1 u primeprime + u = minus F (u) with u =
2u2 r
ε =
3
Effective Potential
2
V (r) = U(r) + 2micror2
Keplerian Orbits
k α U(r) = minus = ε cos θ + 1
r r
α = 2
ε = 1 +2E2
τ 2 =4π2micro
a 3
microk microk2 k α α
rmin = a(1 minus ε) = rmax = a(1 + ε) =1 + ε 1 minus ε
Spherical Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Inelastic Scattering (coefficient of restitution)
|v2 minus v1||u2 minus u1|
Scattering
dσ dσ b db σ(θ) = = =
dΩ dφ sin θdθ sin θ dθ sin θ π θ
tan ψ = ζ = minus cos θ + (m1m2) 2 2
Vector in fixed frame expressed in terms of vector in rotating frame and rotation velocity
dX dX( )inertial = ( )rotating + (ω times X )dt dt
Acceleration in accelerated and rotating frame
a = g minus V minus (ω times r) minus 2(ω times v) minus (ω times (ω times r))
Useful Trigonometrical Formulas
sin(A + B) = sin A cos B + cos A sin B
cos(A + B) = cos A cos B minus sin A sin B
4
Problem 1 Canonical Transformation (35 points)
Consider a harmonic oscillator with Hamiltonian
p2 mω2q2
H = + 2m 2
Introduce transformation of variables from q(t) and p(t) to Q(t) = q(t + τ) and P (t) = p(t + τ) where τ is constant The goal of this problem is to find generating function F (Q q) of this canonical transformation of variables
a) Solve Hamilton equations of motion and find q(t) and p(t) for arbitrary initial conditions
b) Express P and p as functions of only q Q m ω and τ You may want first to express Q and P as the functions of q and p and then rearrange equations Note that there should be no time dependence in these expressions
c) Integrate p as a function of q to obtain q-dependence of F Remember to include the undetermined integrating constant(q) C(Q)
d) Use equation for P (Q q) to find C(Q) and determine F (Q q)
e) Verify that F (Q q) is the correct generating function
5
Problem 2 Scattering from a rotationally symmetric surface (30 points)
Consider small particles moving with velocity parallel to the z-axis Particles are scattering from a perfectly elastic and frictionless surface The surface is rotationally symmetric about the z-axis and the shape of the surface is ρ(z) = z3 for z gt 0 We want to find differential scattering cross section σ(θ)
a) Find the relationship between the scattering angle θ and the impact parameter Note that the surface at the impact point can be considered as a perfectly elastic wall tangential to the curve at that point
b) Extract b(θ) and determine the differential cross section
c) Make a sketch of the scattering angle at some representative point ρ(z) for the case of the surface that is frictionless but totally inelastic
d) Make a sketch of the scattering angle at some representative point ρ(z) for the case of surface that is elastic but it has very high friction
6
Problem 3 Motion in rotating frame (35 points)
Consider a cannon located at geographical lattitude of exactly 45o North Cannon can fire identical projectiles in East North West and South directions All projectiles have identical initial speed of v0 = 200 ms and the cannon always points up at exactly 45o to the horizontal In your calculations of the projectile trajectory you can ignore the curvature of the Earth Assume that there is no air resistance
Assume that the radius of the Earth is R = 6 middot106 m and that the angular velocity of Earthrsquos rotation is Ω = 7 middot 10minus5 sminus1 Gravitational acceleration is g = 10 ms2 Do your calculations in the coordinate system where the z-axis is vertical pointing up with 0 at the center of the Earth the x-axis points North and the y-axis points West
a) Assume that the Earth is not rotating Obtain the algebraic formulas and the numericals value for the total range in meters maximum height above the ground in meters and the projectile flight time in seconds
b) Assume now that the Earth is rotating with its usual Ω Write down an expresshy
sion for acceleration ai = (ax ay az) in terms of components of r = (x y z) and Ω v = (x y˙ z) Ignore very small terms proportional to Ω2x Ω2y and replace radicz with R Keep all variables in algebraic form but replace sin 45o and cos 45o with 1 2
Note the following sections can be quite time consuming Start them only after you have finalized the other problems and sections in this quiz
c) The gun is being shot in the four geographical directions ENW S Write down the expressions for acceleration individually for each direction In each case remove the very small terms and find cancellations of terms of roughly equal size Justify your choices Note that some numerical cancellations are possible since the speed of the projectile happens to be very close to the linear speed of the Earthrsquos surface at that lattitude
d) Based on the magnitudes and signs of the terms of a obtained in c) estimate the effect of the earthrsquos rotation on the position of the impact parameter of the projectile for each of the four cases Mark the location of the new impact point as compared to no-rotation impact point (as obtained in a)) on graphs similar to Figure 1 The center of the graph corresponds to the no-rotation impact position Do not do the precise calculations try only to estimate the direction and relative magnitude of the deviation All four graphs should be oriented with North at the top and East to the right
7
x
yNorth
East
West
South
Figure 1 Impact Point Graph
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 3due Wednesday September 27 2006 at 1230 PM
Suggested Reading
Goldstein Chapter 13 14 24 26 27
Problems
Problem 31 (20 pts)
Goldstein Problem 5 Chapter 1 Page 30
Problem 32 (20 pts)
Goldstein Problem 10 Chapter 1 Page 31
Problem 33 (20 pts)
Goldstein Problem 21 Chapter 1 Page 33
Problem 34 (20 pts)
Goldstein Problem 20 Chapter 2 Page 68
Problem 35 (20 pts)
Goldstein Problem 26 Chapter 2 Page 69
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 4due Wednesday October 11 2005 at 1230 PM
Suggested Reading
Goldstein Sections 81 and 82
Problems
Problem 41 (25 pts)
Goldstein Problem 1 Chapter 8 Page 362
Problem 42 (25 pts)
Goldstein Problem 13 Chapter 8 Page 363
Problem 43 (25 pts)
Goldstein Problem 19 Chapter 8 Page 364
Problem 44 (25 pts)
Goldstein Problem 21 Chapter 8 Page 365
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 5due Monday October 18 2006 at 1230 PM
Suggested Reading
Goldstein ChapterSection Canonical Transformations 91-939697
Problems
Problem 51 (20 pts)
Goldstein Chapter 9 Problem 4 page 422
Problem 52 (20 pts)
Goldstein Chapter 9 Problem 9 page 423
Problem 53 (20 pts)
Goldstein Chapter 9 Problem 21 page 424
Problem 54 (20 pts)
Goldstein Chapter 9 Problem 26 page 426
Problem 55 (20 pts)
Goldstein Chapter 9 Problem 31 page 427
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 6due Wednesday October 25 2006 at 1230 PM
Suggested Reading
Goldstein Kepler Problem 31-33
Problems
Problem 61 (25 pts)
Goldstein Chapter 3 Problem 11 page 128
Problem 62 (25 pts)
Goldstein Chapter 3 Problem 18 page 129
Problem 63 (25 pts)
Goldstein Chapter 3 Exercise 19 page 129
Problem 64 (25 pts)
Goldstein Chapter 3 Exercise 21 page 130
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 7due Monday November 6 2006 at 1230 PM (Note unusual date)
Suggested Reading
Goldstein Collisions 310-311 lecture material Marion and Thornton 96-910 (Goldstein doesnrsquot contain a lot about scattering)
Problems
Problem 71 (20 pts)
Marion amp Thornton 9-26
Problem 72 (20 pts)
Marion amp Thornton 9-33
Problem 73 (20 pts)
Marion amp Thornton 9-45
Problem 74 (20 pts)
Marion amp Thornton 9-48
Problem 75 (20 pts)
Marion amp Thornton 9-50
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 8due Monday November 8 2006 at 1230 PM
Suggested Reading
Lecture Material Goldstein Sections 49 410 53 and 54 Also Chapter 10 Marion and Thronton
Problems
Problem 81 (25 pts)
Goldstein Exercise 22 page 183
Problem 82 (25 pts)
Marion and Thornton 10-12
Problem 83 (25 pts)
Marion and Thornton 10-15
Problem 84 (25 pts)
Goldstein Exercise 17 page 235
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 9due Wednesday November 29 2006 at 1230 PM
Suggested Reading
Goldstein Chapter 5
Problems
Problem 91 (25 pts)
Goldstein Derivation 6 page 233 Ignore the last sentence of question c) (Poinsot construction)
Problem 92 (25 pts)
Goldstein Exercise 18 page 235
Problem 93 (25 pts)
Goldstein Exercise 20 page 236
Problem 94 (25 pts)
Goldstein Exercise 29 page 237
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 10due Wednesday December 6 2006 at 1230 PM
Suggested Reading
Goldstein Sections 15 85 and Chapter 13
Problems
Problem 101 (25 pts)
Goldstein Exercise 1 page 598
Problem 102 (25 pts)
Goldstein Exercise 3 page 599
Problem 103 (25 pts)
Goldstein Exercise 4 page 599
Problem 104 (25 pts)
Goldstein Exercise 12 page 600
1
Massachusetts Institute of Technology Department of Physics
Course 809 Classical Mechanics Term Fall 2006
Quiz 1 October 4 2006
Instructions
bull Do not start until you are told to do so
bull Solve all problems
bull Put your name on the covers of all notebooks you are using
bull Show all work neatly in the blue book label the problem you are working on
bull Mark the final answers
bull Books and notes are not to be used Calculators are unnecessary
2
Useful Formulae
Newton and Basic Kinematics
F = p = ma for v c t=t
v = v0 +
dta t=0
t=t =t
r = r0 + v0t +
dt t
dtF (t)m t=0 t =0
Lagrangian and Hamiltonian
L(q q) = T minus U H(p q) = T + U = pq minus L
Euler-Lagrange (without and with constraints)
partL d partL partL d partL partgaminus = 0 minus + λa = 0 partx dt partx partx dt partx partxa
Polar Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Cylindrical Coordinates
x = r cos φ y = r sin φ z = z
Possibly useful integrals
dx dx = arctan(x) = arctanh(x)
1 + x2 1 minus x2
3
Problem 1 Variable Length Pendulum (35 points)
Consider a simple pendulum consisting of mass m attached to a string of length L After the pendulum is set into motion (at t = 0) the length of the string is lenghtened at a constant rate
dL = α = constant
dt The suspension point remains fixed
a) How many degrees of freedom does the system have
b) Write the Lagrangian for the pendulum Calculate partL is it equal to zero partt
c) Write the equations of motion for the pendulum do not solve Show that the equations of motion become the equations of the fixed length pendulum for α = 0
d) Write the Hamiltonian for the system
e) Calculate the total mechanical energy of the system Compare to the Hamiltoshynian
f) The energy of the system is not conserved What is the rate of change Give physical interpretation of the sources and magnitude of power flowing in or out of the system
Problem 2 Particle on a rotating wire (35 points)
A particle of mass m is constrained to move along a straight frictionless wire The wire is rotating in a vertical plane at a constant angular velocity Ω as shown in the Figure 1 The system is in the gravitational field with gravitational acceleration g pointing downwards At t = 0 the mass was stationary with respect to the wire and it was at a distance R0 from the axis of rotation
a) Write the Lagrangian for a free mass constrained to the vertical plane in gravishytational field using polar coordinate system
b) Write explicitly the constraint equations that force the mass to remain on the rotating wire
c) Write equations of motion for all the coordinates introducing Lagrange Multiplishyers
4
m
g
R0 Ω
Figure 1 Particle on a rotating wire
d) Obtain the expressions for the forces of constraints Give the physical interpreshytation of these forces
e) For sufficiently large Ω the mass will be moving away from the rotation axis for all wire positions What is the minimum value of the angular velocity such that this is guaranteed
Problem 3 Double Pendulum (30 points)
Consider a system consisting of two masses m1 and m2 and connected with massless rigid rods of length L1 and L2 (see Figure 2) As the pendulum moves both masses remain in the vertical plane
L1
g
m 1
L 2
m 2
Figure 2 Double Pendulum
a) How many degrees of freedom does the system have
b) Write the Lagrangian for the system
c) Write equations of motion for the system Do not solve
Massachusetts Institute of Technology Department of Physics
Course 809 Classical Mechanics Term Fall 2006
Quiz 2 November 15 2006
Instructions
bull Do not start until you are told to do so
bull Solve all problems
bull Put your name on the covers of all notebooks you are using
bull Show all work neatly in the white book label the problem you are working on
bull Mark the final answers
bull Books and notes are not to be used You may use your calculator
2
Useful Formulae
Newton and Basic Kinematics
F = p = ma for v c t=t v = v0 + dtprimea
t=0 t=t t=t
r = r0 + v0t + dtprime dtprimeprimeF (tprimeprime)m t=0 t =0
Gravitational Law
F = minus Gm1m2
r122r12
Lagrangian and Hamiltonian
partqL(q q) = T minus U H(p q) = T + U = p minus L
partt
Hamilton Equation of Motion
partH partH = minusp = q
partq partp
Generating function
partF (Q q) partF (Q q) = p = minusP
partq partQ
Poisson Brackets
partg partf partg partf [g f ] = minus
partq partp partp partq
Euler-Lagrange (without and with constraints)
partL d partL partL d partL partgminus = 0 minus + λ = 0 partx dt partx partx dt partx partx
Polar Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Orbit Equation
micro 1 u primeprime + u = minus F (u) with u =
2u2 r
ε =
3
Effective Potential
2
V (r) = U(r) + 2micror2
Keplerian Orbits
k α U(r) = minus = ε cos θ + 1
r r
α = 2
ε = 1 +2E2
τ 2 =4π2micro
a 3
microk microk2 k α α
rmin = a(1 minus ε) = rmax = a(1 + ε) =1 + ε 1 minus ε
Spherical Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Inelastic Scattering (coefficient of restitution)
|v2 minus v1||u2 minus u1|
Scattering
dσ dσ b db σ(θ) = = =
dΩ dφ sin θdθ sin θ dθ sin θ π θ
tan ψ = ζ = minus cos θ + (m1m2) 2 2
Vector in fixed frame expressed in terms of vector in rotating frame and rotation velocity
dX dX( )inertial = ( )rotating + (ω times X )dt dt
Acceleration in accelerated and rotating frame
a = g minus V minus (ω times r) minus 2(ω times v) minus (ω times (ω times r))
Useful Trigonometrical Formulas
sin(A + B) = sin A cos B + cos A sin B
cos(A + B) = cos A cos B minus sin A sin B
4
Problem 1 Canonical Transformation (35 points)
Consider a harmonic oscillator with Hamiltonian
p2 mω2q2
H = + 2m 2
Introduce transformation of variables from q(t) and p(t) to Q(t) = q(t + τ) and P (t) = p(t + τ) where τ is constant The goal of this problem is to find generating function F (Q q) of this canonical transformation of variables
a) Solve Hamilton equations of motion and find q(t) and p(t) for arbitrary initial conditions
b) Express P and p as functions of only q Q m ω and τ You may want first to express Q and P as the functions of q and p and then rearrange equations Note that there should be no time dependence in these expressions
c) Integrate p as a function of q to obtain q-dependence of F Remember to include the undetermined integrating constant(q) C(Q)
d) Use equation for P (Q q) to find C(Q) and determine F (Q q)
e) Verify that F (Q q) is the correct generating function
5
Problem 2 Scattering from a rotationally symmetric surface (30 points)
Consider small particles moving with velocity parallel to the z-axis Particles are scattering from a perfectly elastic and frictionless surface The surface is rotationally symmetric about the z-axis and the shape of the surface is ρ(z) = z3 for z gt 0 We want to find differential scattering cross section σ(θ)
a) Find the relationship between the scattering angle θ and the impact parameter Note that the surface at the impact point can be considered as a perfectly elastic wall tangential to the curve at that point
b) Extract b(θ) and determine the differential cross section
c) Make a sketch of the scattering angle at some representative point ρ(z) for the case of the surface that is frictionless but totally inelastic
d) Make a sketch of the scattering angle at some representative point ρ(z) for the case of surface that is elastic but it has very high friction
6
Problem 3 Motion in rotating frame (35 points)
Consider a cannon located at geographical lattitude of exactly 45o North Cannon can fire identical projectiles in East North West and South directions All projectiles have identical initial speed of v0 = 200 ms and the cannon always points up at exactly 45o to the horizontal In your calculations of the projectile trajectory you can ignore the curvature of the Earth Assume that there is no air resistance
Assume that the radius of the Earth is R = 6 middot106 m and that the angular velocity of Earthrsquos rotation is Ω = 7 middot 10minus5 sminus1 Gravitational acceleration is g = 10 ms2 Do your calculations in the coordinate system where the z-axis is vertical pointing up with 0 at the center of the Earth the x-axis points North and the y-axis points West
a) Assume that the Earth is not rotating Obtain the algebraic formulas and the numericals value for the total range in meters maximum height above the ground in meters and the projectile flight time in seconds
b) Assume now that the Earth is rotating with its usual Ω Write down an expresshy
sion for acceleration ai = (ax ay az) in terms of components of r = (x y z) and Ω v = (x y˙ z) Ignore very small terms proportional to Ω2x Ω2y and replace radicz with R Keep all variables in algebraic form but replace sin 45o and cos 45o with 1 2
Note the following sections can be quite time consuming Start them only after you have finalized the other problems and sections in this quiz
c) The gun is being shot in the four geographical directions ENW S Write down the expressions for acceleration individually for each direction In each case remove the very small terms and find cancellations of terms of roughly equal size Justify your choices Note that some numerical cancellations are possible since the speed of the projectile happens to be very close to the linear speed of the Earthrsquos surface at that lattitude
d) Based on the magnitudes and signs of the terms of a obtained in c) estimate the effect of the earthrsquos rotation on the position of the impact parameter of the projectile for each of the four cases Mark the location of the new impact point as compared to no-rotation impact point (as obtained in a)) on graphs similar to Figure 1 The center of the graph corresponds to the no-rotation impact position Do not do the precise calculations try only to estimate the direction and relative magnitude of the deviation All four graphs should be oriented with North at the top and East to the right
7
x
yNorth
East
West
South
Figure 1 Impact Point Graph
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 4due Wednesday October 11 2005 at 1230 PM
Suggested Reading
Goldstein Sections 81 and 82
Problems
Problem 41 (25 pts)
Goldstein Problem 1 Chapter 8 Page 362
Problem 42 (25 pts)
Goldstein Problem 13 Chapter 8 Page 363
Problem 43 (25 pts)
Goldstein Problem 19 Chapter 8 Page 364
Problem 44 (25 pts)
Goldstein Problem 21 Chapter 8 Page 365
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 5due Monday October 18 2006 at 1230 PM
Suggested Reading
Goldstein ChapterSection Canonical Transformations 91-939697
Problems
Problem 51 (20 pts)
Goldstein Chapter 9 Problem 4 page 422
Problem 52 (20 pts)
Goldstein Chapter 9 Problem 9 page 423
Problem 53 (20 pts)
Goldstein Chapter 9 Problem 21 page 424
Problem 54 (20 pts)
Goldstein Chapter 9 Problem 26 page 426
Problem 55 (20 pts)
Goldstein Chapter 9 Problem 31 page 427
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 6due Wednesday October 25 2006 at 1230 PM
Suggested Reading
Goldstein Kepler Problem 31-33
Problems
Problem 61 (25 pts)
Goldstein Chapter 3 Problem 11 page 128
Problem 62 (25 pts)
Goldstein Chapter 3 Problem 18 page 129
Problem 63 (25 pts)
Goldstein Chapter 3 Exercise 19 page 129
Problem 64 (25 pts)
Goldstein Chapter 3 Exercise 21 page 130
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 7due Monday November 6 2006 at 1230 PM (Note unusual date)
Suggested Reading
Goldstein Collisions 310-311 lecture material Marion and Thornton 96-910 (Goldstein doesnrsquot contain a lot about scattering)
Problems
Problem 71 (20 pts)
Marion amp Thornton 9-26
Problem 72 (20 pts)
Marion amp Thornton 9-33
Problem 73 (20 pts)
Marion amp Thornton 9-45
Problem 74 (20 pts)
Marion amp Thornton 9-48
Problem 75 (20 pts)
Marion amp Thornton 9-50
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 8due Monday November 8 2006 at 1230 PM
Suggested Reading
Lecture Material Goldstein Sections 49 410 53 and 54 Also Chapter 10 Marion and Thronton
Problems
Problem 81 (25 pts)
Goldstein Exercise 22 page 183
Problem 82 (25 pts)
Marion and Thornton 10-12
Problem 83 (25 pts)
Marion and Thornton 10-15
Problem 84 (25 pts)
Goldstein Exercise 17 page 235
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 9due Wednesday November 29 2006 at 1230 PM
Suggested Reading
Goldstein Chapter 5
Problems
Problem 91 (25 pts)
Goldstein Derivation 6 page 233 Ignore the last sentence of question c) (Poinsot construction)
Problem 92 (25 pts)
Goldstein Exercise 18 page 235
Problem 93 (25 pts)
Goldstein Exercise 20 page 236
Problem 94 (25 pts)
Goldstein Exercise 29 page 237
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 10due Wednesday December 6 2006 at 1230 PM
Suggested Reading
Goldstein Sections 15 85 and Chapter 13
Problems
Problem 101 (25 pts)
Goldstein Exercise 1 page 598
Problem 102 (25 pts)
Goldstein Exercise 3 page 599
Problem 103 (25 pts)
Goldstein Exercise 4 page 599
Problem 104 (25 pts)
Goldstein Exercise 12 page 600
1
Massachusetts Institute of Technology Department of Physics
Course 809 Classical Mechanics Term Fall 2006
Quiz 1 October 4 2006
Instructions
bull Do not start until you are told to do so
bull Solve all problems
bull Put your name on the covers of all notebooks you are using
bull Show all work neatly in the blue book label the problem you are working on
bull Mark the final answers
bull Books and notes are not to be used Calculators are unnecessary
2
Useful Formulae
Newton and Basic Kinematics
F = p = ma for v c t=t
v = v0 +
dta t=0
t=t =t
r = r0 + v0t +
dt t
dtF (t)m t=0 t =0
Lagrangian and Hamiltonian
L(q q) = T minus U H(p q) = T + U = pq minus L
Euler-Lagrange (without and with constraints)
partL d partL partL d partL partgaminus = 0 minus + λa = 0 partx dt partx partx dt partx partxa
Polar Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Cylindrical Coordinates
x = r cos φ y = r sin φ z = z
Possibly useful integrals
dx dx = arctan(x) = arctanh(x)
1 + x2 1 minus x2
3
Problem 1 Variable Length Pendulum (35 points)
Consider a simple pendulum consisting of mass m attached to a string of length L After the pendulum is set into motion (at t = 0) the length of the string is lenghtened at a constant rate
dL = α = constant
dt The suspension point remains fixed
a) How many degrees of freedom does the system have
b) Write the Lagrangian for the pendulum Calculate partL is it equal to zero partt
c) Write the equations of motion for the pendulum do not solve Show that the equations of motion become the equations of the fixed length pendulum for α = 0
d) Write the Hamiltonian for the system
e) Calculate the total mechanical energy of the system Compare to the Hamiltoshynian
f) The energy of the system is not conserved What is the rate of change Give physical interpretation of the sources and magnitude of power flowing in or out of the system
Problem 2 Particle on a rotating wire (35 points)
A particle of mass m is constrained to move along a straight frictionless wire The wire is rotating in a vertical plane at a constant angular velocity Ω as shown in the Figure 1 The system is in the gravitational field with gravitational acceleration g pointing downwards At t = 0 the mass was stationary with respect to the wire and it was at a distance R0 from the axis of rotation
a) Write the Lagrangian for a free mass constrained to the vertical plane in gravishytational field using polar coordinate system
b) Write explicitly the constraint equations that force the mass to remain on the rotating wire
c) Write equations of motion for all the coordinates introducing Lagrange Multiplishyers
4
m
g
R0 Ω
Figure 1 Particle on a rotating wire
d) Obtain the expressions for the forces of constraints Give the physical interpreshytation of these forces
e) For sufficiently large Ω the mass will be moving away from the rotation axis for all wire positions What is the minimum value of the angular velocity such that this is guaranteed
Problem 3 Double Pendulum (30 points)
Consider a system consisting of two masses m1 and m2 and connected with massless rigid rods of length L1 and L2 (see Figure 2) As the pendulum moves both masses remain in the vertical plane
L1
g
m 1
L 2
m 2
Figure 2 Double Pendulum
a) How many degrees of freedom does the system have
b) Write the Lagrangian for the system
c) Write equations of motion for the system Do not solve
Massachusetts Institute of Technology Department of Physics
Course 809 Classical Mechanics Term Fall 2006
Quiz 2 November 15 2006
Instructions
bull Do not start until you are told to do so
bull Solve all problems
bull Put your name on the covers of all notebooks you are using
bull Show all work neatly in the white book label the problem you are working on
bull Mark the final answers
bull Books and notes are not to be used You may use your calculator
2
Useful Formulae
Newton and Basic Kinematics
F = p = ma for v c t=t v = v0 + dtprimea
t=0 t=t t=t
r = r0 + v0t + dtprime dtprimeprimeF (tprimeprime)m t=0 t =0
Gravitational Law
F = minus Gm1m2
r122r12
Lagrangian and Hamiltonian
partqL(q q) = T minus U H(p q) = T + U = p minus L
partt
Hamilton Equation of Motion
partH partH = minusp = q
partq partp
Generating function
partF (Q q) partF (Q q) = p = minusP
partq partQ
Poisson Brackets
partg partf partg partf [g f ] = minus
partq partp partp partq
Euler-Lagrange (without and with constraints)
partL d partL partL d partL partgminus = 0 minus + λ = 0 partx dt partx partx dt partx partx
Polar Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Orbit Equation
micro 1 u primeprime + u = minus F (u) with u =
2u2 r
ε =
3
Effective Potential
2
V (r) = U(r) + 2micror2
Keplerian Orbits
k α U(r) = minus = ε cos θ + 1
r r
α = 2
ε = 1 +2E2
τ 2 =4π2micro
a 3
microk microk2 k α α
rmin = a(1 minus ε) = rmax = a(1 + ε) =1 + ε 1 minus ε
Spherical Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Inelastic Scattering (coefficient of restitution)
|v2 minus v1||u2 minus u1|
Scattering
dσ dσ b db σ(θ) = = =
dΩ dφ sin θdθ sin θ dθ sin θ π θ
tan ψ = ζ = minus cos θ + (m1m2) 2 2
Vector in fixed frame expressed in terms of vector in rotating frame and rotation velocity
dX dX( )inertial = ( )rotating + (ω times X )dt dt
Acceleration in accelerated and rotating frame
a = g minus V minus (ω times r) minus 2(ω times v) minus (ω times (ω times r))
Useful Trigonometrical Formulas
sin(A + B) = sin A cos B + cos A sin B
cos(A + B) = cos A cos B minus sin A sin B
4
Problem 1 Canonical Transformation (35 points)
Consider a harmonic oscillator with Hamiltonian
p2 mω2q2
H = + 2m 2
Introduce transformation of variables from q(t) and p(t) to Q(t) = q(t + τ) and P (t) = p(t + τ) where τ is constant The goal of this problem is to find generating function F (Q q) of this canonical transformation of variables
a) Solve Hamilton equations of motion and find q(t) and p(t) for arbitrary initial conditions
b) Express P and p as functions of only q Q m ω and τ You may want first to express Q and P as the functions of q and p and then rearrange equations Note that there should be no time dependence in these expressions
c) Integrate p as a function of q to obtain q-dependence of F Remember to include the undetermined integrating constant(q) C(Q)
d) Use equation for P (Q q) to find C(Q) and determine F (Q q)
e) Verify that F (Q q) is the correct generating function
5
Problem 2 Scattering from a rotationally symmetric surface (30 points)
Consider small particles moving with velocity parallel to the z-axis Particles are scattering from a perfectly elastic and frictionless surface The surface is rotationally symmetric about the z-axis and the shape of the surface is ρ(z) = z3 for z gt 0 We want to find differential scattering cross section σ(θ)
a) Find the relationship between the scattering angle θ and the impact parameter Note that the surface at the impact point can be considered as a perfectly elastic wall tangential to the curve at that point
b) Extract b(θ) and determine the differential cross section
c) Make a sketch of the scattering angle at some representative point ρ(z) for the case of the surface that is frictionless but totally inelastic
d) Make a sketch of the scattering angle at some representative point ρ(z) for the case of surface that is elastic but it has very high friction
6
Problem 3 Motion in rotating frame (35 points)
Consider a cannon located at geographical lattitude of exactly 45o North Cannon can fire identical projectiles in East North West and South directions All projectiles have identical initial speed of v0 = 200 ms and the cannon always points up at exactly 45o to the horizontal In your calculations of the projectile trajectory you can ignore the curvature of the Earth Assume that there is no air resistance
Assume that the radius of the Earth is R = 6 middot106 m and that the angular velocity of Earthrsquos rotation is Ω = 7 middot 10minus5 sminus1 Gravitational acceleration is g = 10 ms2 Do your calculations in the coordinate system where the z-axis is vertical pointing up with 0 at the center of the Earth the x-axis points North and the y-axis points West
a) Assume that the Earth is not rotating Obtain the algebraic formulas and the numericals value for the total range in meters maximum height above the ground in meters and the projectile flight time in seconds
b) Assume now that the Earth is rotating with its usual Ω Write down an expresshy
sion for acceleration ai = (ax ay az) in terms of components of r = (x y z) and Ω v = (x y˙ z) Ignore very small terms proportional to Ω2x Ω2y and replace radicz with R Keep all variables in algebraic form but replace sin 45o and cos 45o with 1 2
Note the following sections can be quite time consuming Start them only after you have finalized the other problems and sections in this quiz
c) The gun is being shot in the four geographical directions ENW S Write down the expressions for acceleration individually for each direction In each case remove the very small terms and find cancellations of terms of roughly equal size Justify your choices Note that some numerical cancellations are possible since the speed of the projectile happens to be very close to the linear speed of the Earthrsquos surface at that lattitude
d) Based on the magnitudes and signs of the terms of a obtained in c) estimate the effect of the earthrsquos rotation on the position of the impact parameter of the projectile for each of the four cases Mark the location of the new impact point as compared to no-rotation impact point (as obtained in a)) on graphs similar to Figure 1 The center of the graph corresponds to the no-rotation impact position Do not do the precise calculations try only to estimate the direction and relative magnitude of the deviation All four graphs should be oriented with North at the top and East to the right
7
x
yNorth
East
West
South
Figure 1 Impact Point Graph
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 5due Monday October 18 2006 at 1230 PM
Suggested Reading
Goldstein ChapterSection Canonical Transformations 91-939697
Problems
Problem 51 (20 pts)
Goldstein Chapter 9 Problem 4 page 422
Problem 52 (20 pts)
Goldstein Chapter 9 Problem 9 page 423
Problem 53 (20 pts)
Goldstein Chapter 9 Problem 21 page 424
Problem 54 (20 pts)
Goldstein Chapter 9 Problem 26 page 426
Problem 55 (20 pts)
Goldstein Chapter 9 Problem 31 page 427
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 6due Wednesday October 25 2006 at 1230 PM
Suggested Reading
Goldstein Kepler Problem 31-33
Problems
Problem 61 (25 pts)
Goldstein Chapter 3 Problem 11 page 128
Problem 62 (25 pts)
Goldstein Chapter 3 Problem 18 page 129
Problem 63 (25 pts)
Goldstein Chapter 3 Exercise 19 page 129
Problem 64 (25 pts)
Goldstein Chapter 3 Exercise 21 page 130
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 7due Monday November 6 2006 at 1230 PM (Note unusual date)
Suggested Reading
Goldstein Collisions 310-311 lecture material Marion and Thornton 96-910 (Goldstein doesnrsquot contain a lot about scattering)
Problems
Problem 71 (20 pts)
Marion amp Thornton 9-26
Problem 72 (20 pts)
Marion amp Thornton 9-33
Problem 73 (20 pts)
Marion amp Thornton 9-45
Problem 74 (20 pts)
Marion amp Thornton 9-48
Problem 75 (20 pts)
Marion amp Thornton 9-50
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 8due Monday November 8 2006 at 1230 PM
Suggested Reading
Lecture Material Goldstein Sections 49 410 53 and 54 Also Chapter 10 Marion and Thronton
Problems
Problem 81 (25 pts)
Goldstein Exercise 22 page 183
Problem 82 (25 pts)
Marion and Thornton 10-12
Problem 83 (25 pts)
Marion and Thornton 10-15
Problem 84 (25 pts)
Goldstein Exercise 17 page 235
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 9due Wednesday November 29 2006 at 1230 PM
Suggested Reading
Goldstein Chapter 5
Problems
Problem 91 (25 pts)
Goldstein Derivation 6 page 233 Ignore the last sentence of question c) (Poinsot construction)
Problem 92 (25 pts)
Goldstein Exercise 18 page 235
Problem 93 (25 pts)
Goldstein Exercise 20 page 236
Problem 94 (25 pts)
Goldstein Exercise 29 page 237
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 10due Wednesday December 6 2006 at 1230 PM
Suggested Reading
Goldstein Sections 15 85 and Chapter 13
Problems
Problem 101 (25 pts)
Goldstein Exercise 1 page 598
Problem 102 (25 pts)
Goldstein Exercise 3 page 599
Problem 103 (25 pts)
Goldstein Exercise 4 page 599
Problem 104 (25 pts)
Goldstein Exercise 12 page 600
1
Massachusetts Institute of Technology Department of Physics
Course 809 Classical Mechanics Term Fall 2006
Quiz 1 October 4 2006
Instructions
bull Do not start until you are told to do so
bull Solve all problems
bull Put your name on the covers of all notebooks you are using
bull Show all work neatly in the blue book label the problem you are working on
bull Mark the final answers
bull Books and notes are not to be used Calculators are unnecessary
2
Useful Formulae
Newton and Basic Kinematics
F = p = ma for v c t=t
v = v0 +
dta t=0
t=t =t
r = r0 + v0t +
dt t
dtF (t)m t=0 t =0
Lagrangian and Hamiltonian
L(q q) = T minus U H(p q) = T + U = pq minus L
Euler-Lagrange (without and with constraints)
partL d partL partL d partL partgaminus = 0 minus + λa = 0 partx dt partx partx dt partx partxa
Polar Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Cylindrical Coordinates
x = r cos φ y = r sin φ z = z
Possibly useful integrals
dx dx = arctan(x) = arctanh(x)
1 + x2 1 minus x2
3
Problem 1 Variable Length Pendulum (35 points)
Consider a simple pendulum consisting of mass m attached to a string of length L After the pendulum is set into motion (at t = 0) the length of the string is lenghtened at a constant rate
dL = α = constant
dt The suspension point remains fixed
a) How many degrees of freedom does the system have
b) Write the Lagrangian for the pendulum Calculate partL is it equal to zero partt
c) Write the equations of motion for the pendulum do not solve Show that the equations of motion become the equations of the fixed length pendulum for α = 0
d) Write the Hamiltonian for the system
e) Calculate the total mechanical energy of the system Compare to the Hamiltoshynian
f) The energy of the system is not conserved What is the rate of change Give physical interpretation of the sources and magnitude of power flowing in or out of the system
Problem 2 Particle on a rotating wire (35 points)
A particle of mass m is constrained to move along a straight frictionless wire The wire is rotating in a vertical plane at a constant angular velocity Ω as shown in the Figure 1 The system is in the gravitational field with gravitational acceleration g pointing downwards At t = 0 the mass was stationary with respect to the wire and it was at a distance R0 from the axis of rotation
a) Write the Lagrangian for a free mass constrained to the vertical plane in gravishytational field using polar coordinate system
b) Write explicitly the constraint equations that force the mass to remain on the rotating wire
c) Write equations of motion for all the coordinates introducing Lagrange Multiplishyers
4
m
g
R0 Ω
Figure 1 Particle on a rotating wire
d) Obtain the expressions for the forces of constraints Give the physical interpreshytation of these forces
e) For sufficiently large Ω the mass will be moving away from the rotation axis for all wire positions What is the minimum value of the angular velocity such that this is guaranteed
Problem 3 Double Pendulum (30 points)
Consider a system consisting of two masses m1 and m2 and connected with massless rigid rods of length L1 and L2 (see Figure 2) As the pendulum moves both masses remain in the vertical plane
L1
g
m 1
L 2
m 2
Figure 2 Double Pendulum
a) How many degrees of freedom does the system have
b) Write the Lagrangian for the system
c) Write equations of motion for the system Do not solve
Massachusetts Institute of Technology Department of Physics
Course 809 Classical Mechanics Term Fall 2006
Quiz 2 November 15 2006
Instructions
bull Do not start until you are told to do so
bull Solve all problems
bull Put your name on the covers of all notebooks you are using
bull Show all work neatly in the white book label the problem you are working on
bull Mark the final answers
bull Books and notes are not to be used You may use your calculator
2
Useful Formulae
Newton and Basic Kinematics
F = p = ma for v c t=t v = v0 + dtprimea
t=0 t=t t=t
r = r0 + v0t + dtprime dtprimeprimeF (tprimeprime)m t=0 t =0
Gravitational Law
F = minus Gm1m2
r122r12
Lagrangian and Hamiltonian
partqL(q q) = T minus U H(p q) = T + U = p minus L
partt
Hamilton Equation of Motion
partH partH = minusp = q
partq partp
Generating function
partF (Q q) partF (Q q) = p = minusP
partq partQ
Poisson Brackets
partg partf partg partf [g f ] = minus
partq partp partp partq
Euler-Lagrange (without and with constraints)
partL d partL partL d partL partgminus = 0 minus + λ = 0 partx dt partx partx dt partx partx
Polar Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Orbit Equation
micro 1 u primeprime + u = minus F (u) with u =
2u2 r
ε =
3
Effective Potential
2
V (r) = U(r) + 2micror2
Keplerian Orbits
k α U(r) = minus = ε cos θ + 1
r r
α = 2
ε = 1 +2E2
τ 2 =4π2micro
a 3
microk microk2 k α α
rmin = a(1 minus ε) = rmax = a(1 + ε) =1 + ε 1 minus ε
Spherical Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Inelastic Scattering (coefficient of restitution)
|v2 minus v1||u2 minus u1|
Scattering
dσ dσ b db σ(θ) = = =
dΩ dφ sin θdθ sin θ dθ sin θ π θ
tan ψ = ζ = minus cos θ + (m1m2) 2 2
Vector in fixed frame expressed in terms of vector in rotating frame and rotation velocity
dX dX( )inertial = ( )rotating + (ω times X )dt dt
Acceleration in accelerated and rotating frame
a = g minus V minus (ω times r) minus 2(ω times v) minus (ω times (ω times r))
Useful Trigonometrical Formulas
sin(A + B) = sin A cos B + cos A sin B
cos(A + B) = cos A cos B minus sin A sin B
4
Problem 1 Canonical Transformation (35 points)
Consider a harmonic oscillator with Hamiltonian
p2 mω2q2
H = + 2m 2
Introduce transformation of variables from q(t) and p(t) to Q(t) = q(t + τ) and P (t) = p(t + τ) where τ is constant The goal of this problem is to find generating function F (Q q) of this canonical transformation of variables
a) Solve Hamilton equations of motion and find q(t) and p(t) for arbitrary initial conditions
b) Express P and p as functions of only q Q m ω and τ You may want first to express Q and P as the functions of q and p and then rearrange equations Note that there should be no time dependence in these expressions
c) Integrate p as a function of q to obtain q-dependence of F Remember to include the undetermined integrating constant(q) C(Q)
d) Use equation for P (Q q) to find C(Q) and determine F (Q q)
e) Verify that F (Q q) is the correct generating function
5
Problem 2 Scattering from a rotationally symmetric surface (30 points)
Consider small particles moving with velocity parallel to the z-axis Particles are scattering from a perfectly elastic and frictionless surface The surface is rotationally symmetric about the z-axis and the shape of the surface is ρ(z) = z3 for z gt 0 We want to find differential scattering cross section σ(θ)
a) Find the relationship between the scattering angle θ and the impact parameter Note that the surface at the impact point can be considered as a perfectly elastic wall tangential to the curve at that point
b) Extract b(θ) and determine the differential cross section
c) Make a sketch of the scattering angle at some representative point ρ(z) for the case of the surface that is frictionless but totally inelastic
d) Make a sketch of the scattering angle at some representative point ρ(z) for the case of surface that is elastic but it has very high friction
6
Problem 3 Motion in rotating frame (35 points)
Consider a cannon located at geographical lattitude of exactly 45o North Cannon can fire identical projectiles in East North West and South directions All projectiles have identical initial speed of v0 = 200 ms and the cannon always points up at exactly 45o to the horizontal In your calculations of the projectile trajectory you can ignore the curvature of the Earth Assume that there is no air resistance
Assume that the radius of the Earth is R = 6 middot106 m and that the angular velocity of Earthrsquos rotation is Ω = 7 middot 10minus5 sminus1 Gravitational acceleration is g = 10 ms2 Do your calculations in the coordinate system where the z-axis is vertical pointing up with 0 at the center of the Earth the x-axis points North and the y-axis points West
a) Assume that the Earth is not rotating Obtain the algebraic formulas and the numericals value for the total range in meters maximum height above the ground in meters and the projectile flight time in seconds
b) Assume now that the Earth is rotating with its usual Ω Write down an expresshy
sion for acceleration ai = (ax ay az) in terms of components of r = (x y z) and Ω v = (x y˙ z) Ignore very small terms proportional to Ω2x Ω2y and replace radicz with R Keep all variables in algebraic form but replace sin 45o and cos 45o with 1 2
Note the following sections can be quite time consuming Start them only after you have finalized the other problems and sections in this quiz
c) The gun is being shot in the four geographical directions ENW S Write down the expressions for acceleration individually for each direction In each case remove the very small terms and find cancellations of terms of roughly equal size Justify your choices Note that some numerical cancellations are possible since the speed of the projectile happens to be very close to the linear speed of the Earthrsquos surface at that lattitude
d) Based on the magnitudes and signs of the terms of a obtained in c) estimate the effect of the earthrsquos rotation on the position of the impact parameter of the projectile for each of the four cases Mark the location of the new impact point as compared to no-rotation impact point (as obtained in a)) on graphs similar to Figure 1 The center of the graph corresponds to the no-rotation impact position Do not do the precise calculations try only to estimate the direction and relative magnitude of the deviation All four graphs should be oriented with North at the top and East to the right
7
x
yNorth
East
West
South
Figure 1 Impact Point Graph
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 6due Wednesday October 25 2006 at 1230 PM
Suggested Reading
Goldstein Kepler Problem 31-33
Problems
Problem 61 (25 pts)
Goldstein Chapter 3 Problem 11 page 128
Problem 62 (25 pts)
Goldstein Chapter 3 Problem 18 page 129
Problem 63 (25 pts)
Goldstein Chapter 3 Exercise 19 page 129
Problem 64 (25 pts)
Goldstein Chapter 3 Exercise 21 page 130
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 7due Monday November 6 2006 at 1230 PM (Note unusual date)
Suggested Reading
Goldstein Collisions 310-311 lecture material Marion and Thornton 96-910 (Goldstein doesnrsquot contain a lot about scattering)
Problems
Problem 71 (20 pts)
Marion amp Thornton 9-26
Problem 72 (20 pts)
Marion amp Thornton 9-33
Problem 73 (20 pts)
Marion amp Thornton 9-45
Problem 74 (20 pts)
Marion amp Thornton 9-48
Problem 75 (20 pts)
Marion amp Thornton 9-50
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 8due Monday November 8 2006 at 1230 PM
Suggested Reading
Lecture Material Goldstein Sections 49 410 53 and 54 Also Chapter 10 Marion and Thronton
Problems
Problem 81 (25 pts)
Goldstein Exercise 22 page 183
Problem 82 (25 pts)
Marion and Thornton 10-12
Problem 83 (25 pts)
Marion and Thornton 10-15
Problem 84 (25 pts)
Goldstein Exercise 17 page 235
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 9due Wednesday November 29 2006 at 1230 PM
Suggested Reading
Goldstein Chapter 5
Problems
Problem 91 (25 pts)
Goldstein Derivation 6 page 233 Ignore the last sentence of question c) (Poinsot construction)
Problem 92 (25 pts)
Goldstein Exercise 18 page 235
Problem 93 (25 pts)
Goldstein Exercise 20 page 236
Problem 94 (25 pts)
Goldstein Exercise 29 page 237
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 10due Wednesday December 6 2006 at 1230 PM
Suggested Reading
Goldstein Sections 15 85 and Chapter 13
Problems
Problem 101 (25 pts)
Goldstein Exercise 1 page 598
Problem 102 (25 pts)
Goldstein Exercise 3 page 599
Problem 103 (25 pts)
Goldstein Exercise 4 page 599
Problem 104 (25 pts)
Goldstein Exercise 12 page 600
1
Massachusetts Institute of Technology Department of Physics
Course 809 Classical Mechanics Term Fall 2006
Quiz 1 October 4 2006
Instructions
bull Do not start until you are told to do so
bull Solve all problems
bull Put your name on the covers of all notebooks you are using
bull Show all work neatly in the blue book label the problem you are working on
bull Mark the final answers
bull Books and notes are not to be used Calculators are unnecessary
2
Useful Formulae
Newton and Basic Kinematics
F = p = ma for v c t=t
v = v0 +
dta t=0
t=t =t
r = r0 + v0t +
dt t
dtF (t)m t=0 t =0
Lagrangian and Hamiltonian
L(q q) = T minus U H(p q) = T + U = pq minus L
Euler-Lagrange (without and with constraints)
partL d partL partL d partL partgaminus = 0 minus + λa = 0 partx dt partx partx dt partx partxa
Polar Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Cylindrical Coordinates
x = r cos φ y = r sin φ z = z
Possibly useful integrals
dx dx = arctan(x) = arctanh(x)
1 + x2 1 minus x2
3
Problem 1 Variable Length Pendulum (35 points)
Consider a simple pendulum consisting of mass m attached to a string of length L After the pendulum is set into motion (at t = 0) the length of the string is lenghtened at a constant rate
dL = α = constant
dt The suspension point remains fixed
a) How many degrees of freedom does the system have
b) Write the Lagrangian for the pendulum Calculate partL is it equal to zero partt
c) Write the equations of motion for the pendulum do not solve Show that the equations of motion become the equations of the fixed length pendulum for α = 0
d) Write the Hamiltonian for the system
e) Calculate the total mechanical energy of the system Compare to the Hamiltoshynian
f) The energy of the system is not conserved What is the rate of change Give physical interpretation of the sources and magnitude of power flowing in or out of the system
Problem 2 Particle on a rotating wire (35 points)
A particle of mass m is constrained to move along a straight frictionless wire The wire is rotating in a vertical plane at a constant angular velocity Ω as shown in the Figure 1 The system is in the gravitational field with gravitational acceleration g pointing downwards At t = 0 the mass was stationary with respect to the wire and it was at a distance R0 from the axis of rotation
a) Write the Lagrangian for a free mass constrained to the vertical plane in gravishytational field using polar coordinate system
b) Write explicitly the constraint equations that force the mass to remain on the rotating wire
c) Write equations of motion for all the coordinates introducing Lagrange Multiplishyers
4
m
g
R0 Ω
Figure 1 Particle on a rotating wire
d) Obtain the expressions for the forces of constraints Give the physical interpreshytation of these forces
e) For sufficiently large Ω the mass will be moving away from the rotation axis for all wire positions What is the minimum value of the angular velocity such that this is guaranteed
Problem 3 Double Pendulum (30 points)
Consider a system consisting of two masses m1 and m2 and connected with massless rigid rods of length L1 and L2 (see Figure 2) As the pendulum moves both masses remain in the vertical plane
L1
g
m 1
L 2
m 2
Figure 2 Double Pendulum
a) How many degrees of freedom does the system have
b) Write the Lagrangian for the system
c) Write equations of motion for the system Do not solve
Massachusetts Institute of Technology Department of Physics
Course 809 Classical Mechanics Term Fall 2006
Quiz 2 November 15 2006
Instructions
bull Do not start until you are told to do so
bull Solve all problems
bull Put your name on the covers of all notebooks you are using
bull Show all work neatly in the white book label the problem you are working on
bull Mark the final answers
bull Books and notes are not to be used You may use your calculator
2
Useful Formulae
Newton and Basic Kinematics
F = p = ma for v c t=t v = v0 + dtprimea
t=0 t=t t=t
r = r0 + v0t + dtprime dtprimeprimeF (tprimeprime)m t=0 t =0
Gravitational Law
F = minus Gm1m2
r122r12
Lagrangian and Hamiltonian
partqL(q q) = T minus U H(p q) = T + U = p minus L
partt
Hamilton Equation of Motion
partH partH = minusp = q
partq partp
Generating function
partF (Q q) partF (Q q) = p = minusP
partq partQ
Poisson Brackets
partg partf partg partf [g f ] = minus
partq partp partp partq
Euler-Lagrange (without and with constraints)
partL d partL partL d partL partgminus = 0 minus + λ = 0 partx dt partx partx dt partx partx
Polar Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Orbit Equation
micro 1 u primeprime + u = minus F (u) with u =
2u2 r
ε =
3
Effective Potential
2
V (r) = U(r) + 2micror2
Keplerian Orbits
k α U(r) = minus = ε cos θ + 1
r r
α = 2
ε = 1 +2E2
τ 2 =4π2micro
a 3
microk microk2 k α α
rmin = a(1 minus ε) = rmax = a(1 + ε) =1 + ε 1 minus ε
Spherical Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Inelastic Scattering (coefficient of restitution)
|v2 minus v1||u2 minus u1|
Scattering
dσ dσ b db σ(θ) = = =
dΩ dφ sin θdθ sin θ dθ sin θ π θ
tan ψ = ζ = minus cos θ + (m1m2) 2 2
Vector in fixed frame expressed in terms of vector in rotating frame and rotation velocity
dX dX( )inertial = ( )rotating + (ω times X )dt dt
Acceleration in accelerated and rotating frame
a = g minus V minus (ω times r) minus 2(ω times v) minus (ω times (ω times r))
Useful Trigonometrical Formulas
sin(A + B) = sin A cos B + cos A sin B
cos(A + B) = cos A cos B minus sin A sin B
4
Problem 1 Canonical Transformation (35 points)
Consider a harmonic oscillator with Hamiltonian
p2 mω2q2
H = + 2m 2
Introduce transformation of variables from q(t) and p(t) to Q(t) = q(t + τ) and P (t) = p(t + τ) where τ is constant The goal of this problem is to find generating function F (Q q) of this canonical transformation of variables
a) Solve Hamilton equations of motion and find q(t) and p(t) for arbitrary initial conditions
b) Express P and p as functions of only q Q m ω and τ You may want first to express Q and P as the functions of q and p and then rearrange equations Note that there should be no time dependence in these expressions
c) Integrate p as a function of q to obtain q-dependence of F Remember to include the undetermined integrating constant(q) C(Q)
d) Use equation for P (Q q) to find C(Q) and determine F (Q q)
e) Verify that F (Q q) is the correct generating function
5
Problem 2 Scattering from a rotationally symmetric surface (30 points)
Consider small particles moving with velocity parallel to the z-axis Particles are scattering from a perfectly elastic and frictionless surface The surface is rotationally symmetric about the z-axis and the shape of the surface is ρ(z) = z3 for z gt 0 We want to find differential scattering cross section σ(θ)
a) Find the relationship between the scattering angle θ and the impact parameter Note that the surface at the impact point can be considered as a perfectly elastic wall tangential to the curve at that point
b) Extract b(θ) and determine the differential cross section
c) Make a sketch of the scattering angle at some representative point ρ(z) for the case of the surface that is frictionless but totally inelastic
d) Make a sketch of the scattering angle at some representative point ρ(z) for the case of surface that is elastic but it has very high friction
6
Problem 3 Motion in rotating frame (35 points)
Consider a cannon located at geographical lattitude of exactly 45o North Cannon can fire identical projectiles in East North West and South directions All projectiles have identical initial speed of v0 = 200 ms and the cannon always points up at exactly 45o to the horizontal In your calculations of the projectile trajectory you can ignore the curvature of the Earth Assume that there is no air resistance
Assume that the radius of the Earth is R = 6 middot106 m and that the angular velocity of Earthrsquos rotation is Ω = 7 middot 10minus5 sminus1 Gravitational acceleration is g = 10 ms2 Do your calculations in the coordinate system where the z-axis is vertical pointing up with 0 at the center of the Earth the x-axis points North and the y-axis points West
a) Assume that the Earth is not rotating Obtain the algebraic formulas and the numericals value for the total range in meters maximum height above the ground in meters and the projectile flight time in seconds
b) Assume now that the Earth is rotating with its usual Ω Write down an expresshy
sion for acceleration ai = (ax ay az) in terms of components of r = (x y z) and Ω v = (x y˙ z) Ignore very small terms proportional to Ω2x Ω2y and replace radicz with R Keep all variables in algebraic form but replace sin 45o and cos 45o with 1 2
Note the following sections can be quite time consuming Start them only after you have finalized the other problems and sections in this quiz
c) The gun is being shot in the four geographical directions ENW S Write down the expressions for acceleration individually for each direction In each case remove the very small terms and find cancellations of terms of roughly equal size Justify your choices Note that some numerical cancellations are possible since the speed of the projectile happens to be very close to the linear speed of the Earthrsquos surface at that lattitude
d) Based on the magnitudes and signs of the terms of a obtained in c) estimate the effect of the earthrsquos rotation on the position of the impact parameter of the projectile for each of the four cases Mark the location of the new impact point as compared to no-rotation impact point (as obtained in a)) on graphs similar to Figure 1 The center of the graph corresponds to the no-rotation impact position Do not do the precise calculations try only to estimate the direction and relative magnitude of the deviation All four graphs should be oriented with North at the top and East to the right
7
x
yNorth
East
West
South
Figure 1 Impact Point Graph
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 7due Monday November 6 2006 at 1230 PM (Note unusual date)
Suggested Reading
Goldstein Collisions 310-311 lecture material Marion and Thornton 96-910 (Goldstein doesnrsquot contain a lot about scattering)
Problems
Problem 71 (20 pts)
Marion amp Thornton 9-26
Problem 72 (20 pts)
Marion amp Thornton 9-33
Problem 73 (20 pts)
Marion amp Thornton 9-45
Problem 74 (20 pts)
Marion amp Thornton 9-48
Problem 75 (20 pts)
Marion amp Thornton 9-50
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 8due Monday November 8 2006 at 1230 PM
Suggested Reading
Lecture Material Goldstein Sections 49 410 53 and 54 Also Chapter 10 Marion and Thronton
Problems
Problem 81 (25 pts)
Goldstein Exercise 22 page 183
Problem 82 (25 pts)
Marion and Thornton 10-12
Problem 83 (25 pts)
Marion and Thornton 10-15
Problem 84 (25 pts)
Goldstein Exercise 17 page 235
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 9due Wednesday November 29 2006 at 1230 PM
Suggested Reading
Goldstein Chapter 5
Problems
Problem 91 (25 pts)
Goldstein Derivation 6 page 233 Ignore the last sentence of question c) (Poinsot construction)
Problem 92 (25 pts)
Goldstein Exercise 18 page 235
Problem 93 (25 pts)
Goldstein Exercise 20 page 236
Problem 94 (25 pts)
Goldstein Exercise 29 page 237
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 10due Wednesday December 6 2006 at 1230 PM
Suggested Reading
Goldstein Sections 15 85 and Chapter 13
Problems
Problem 101 (25 pts)
Goldstein Exercise 1 page 598
Problem 102 (25 pts)
Goldstein Exercise 3 page 599
Problem 103 (25 pts)
Goldstein Exercise 4 page 599
Problem 104 (25 pts)
Goldstein Exercise 12 page 600
1
Massachusetts Institute of Technology Department of Physics
Course 809 Classical Mechanics Term Fall 2006
Quiz 1 October 4 2006
Instructions
bull Do not start until you are told to do so
bull Solve all problems
bull Put your name on the covers of all notebooks you are using
bull Show all work neatly in the blue book label the problem you are working on
bull Mark the final answers
bull Books and notes are not to be used Calculators are unnecessary
2
Useful Formulae
Newton and Basic Kinematics
F = p = ma for v c t=t
v = v0 +
dta t=0
t=t =t
r = r0 + v0t +
dt t
dtF (t)m t=0 t =0
Lagrangian and Hamiltonian
L(q q) = T minus U H(p q) = T + U = pq minus L
Euler-Lagrange (without and with constraints)
partL d partL partL d partL partgaminus = 0 minus + λa = 0 partx dt partx partx dt partx partxa
Polar Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Cylindrical Coordinates
x = r cos φ y = r sin φ z = z
Possibly useful integrals
dx dx = arctan(x) = arctanh(x)
1 + x2 1 minus x2
3
Problem 1 Variable Length Pendulum (35 points)
Consider a simple pendulum consisting of mass m attached to a string of length L After the pendulum is set into motion (at t = 0) the length of the string is lenghtened at a constant rate
dL = α = constant
dt The suspension point remains fixed
a) How many degrees of freedom does the system have
b) Write the Lagrangian for the pendulum Calculate partL is it equal to zero partt
c) Write the equations of motion for the pendulum do not solve Show that the equations of motion become the equations of the fixed length pendulum for α = 0
d) Write the Hamiltonian for the system
e) Calculate the total mechanical energy of the system Compare to the Hamiltoshynian
f) The energy of the system is not conserved What is the rate of change Give physical interpretation of the sources and magnitude of power flowing in or out of the system
Problem 2 Particle on a rotating wire (35 points)
A particle of mass m is constrained to move along a straight frictionless wire The wire is rotating in a vertical plane at a constant angular velocity Ω as shown in the Figure 1 The system is in the gravitational field with gravitational acceleration g pointing downwards At t = 0 the mass was stationary with respect to the wire and it was at a distance R0 from the axis of rotation
a) Write the Lagrangian for a free mass constrained to the vertical plane in gravishytational field using polar coordinate system
b) Write explicitly the constraint equations that force the mass to remain on the rotating wire
c) Write equations of motion for all the coordinates introducing Lagrange Multiplishyers
4
m
g
R0 Ω
Figure 1 Particle on a rotating wire
d) Obtain the expressions for the forces of constraints Give the physical interpreshytation of these forces
e) For sufficiently large Ω the mass will be moving away from the rotation axis for all wire positions What is the minimum value of the angular velocity such that this is guaranteed
Problem 3 Double Pendulum (30 points)
Consider a system consisting of two masses m1 and m2 and connected with massless rigid rods of length L1 and L2 (see Figure 2) As the pendulum moves both masses remain in the vertical plane
L1
g
m 1
L 2
m 2
Figure 2 Double Pendulum
a) How many degrees of freedom does the system have
b) Write the Lagrangian for the system
c) Write equations of motion for the system Do not solve
Massachusetts Institute of Technology Department of Physics
Course 809 Classical Mechanics Term Fall 2006
Quiz 2 November 15 2006
Instructions
bull Do not start until you are told to do so
bull Solve all problems
bull Put your name on the covers of all notebooks you are using
bull Show all work neatly in the white book label the problem you are working on
bull Mark the final answers
bull Books and notes are not to be used You may use your calculator
2
Useful Formulae
Newton and Basic Kinematics
F = p = ma for v c t=t v = v0 + dtprimea
t=0 t=t t=t
r = r0 + v0t + dtprime dtprimeprimeF (tprimeprime)m t=0 t =0
Gravitational Law
F = minus Gm1m2
r122r12
Lagrangian and Hamiltonian
partqL(q q) = T minus U H(p q) = T + U = p minus L
partt
Hamilton Equation of Motion
partH partH = minusp = q
partq partp
Generating function
partF (Q q) partF (Q q) = p = minusP
partq partQ
Poisson Brackets
partg partf partg partf [g f ] = minus
partq partp partp partq
Euler-Lagrange (without and with constraints)
partL d partL partL d partL partgminus = 0 minus + λ = 0 partx dt partx partx dt partx partx
Polar Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Orbit Equation
micro 1 u primeprime + u = minus F (u) with u =
2u2 r
ε =
3
Effective Potential
2
V (r) = U(r) + 2micror2
Keplerian Orbits
k α U(r) = minus = ε cos θ + 1
r r
α = 2
ε = 1 +2E2
τ 2 =4π2micro
a 3
microk microk2 k α α
rmin = a(1 minus ε) = rmax = a(1 + ε) =1 + ε 1 minus ε
Spherical Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Inelastic Scattering (coefficient of restitution)
|v2 minus v1||u2 minus u1|
Scattering
dσ dσ b db σ(θ) = = =
dΩ dφ sin θdθ sin θ dθ sin θ π θ
tan ψ = ζ = minus cos θ + (m1m2) 2 2
Vector in fixed frame expressed in terms of vector in rotating frame and rotation velocity
dX dX( )inertial = ( )rotating + (ω times X )dt dt
Acceleration in accelerated and rotating frame
a = g minus V minus (ω times r) minus 2(ω times v) minus (ω times (ω times r))
Useful Trigonometrical Formulas
sin(A + B) = sin A cos B + cos A sin B
cos(A + B) = cos A cos B minus sin A sin B
4
Problem 1 Canonical Transformation (35 points)
Consider a harmonic oscillator with Hamiltonian
p2 mω2q2
H = + 2m 2
Introduce transformation of variables from q(t) and p(t) to Q(t) = q(t + τ) and P (t) = p(t + τ) where τ is constant The goal of this problem is to find generating function F (Q q) of this canonical transformation of variables
a) Solve Hamilton equations of motion and find q(t) and p(t) for arbitrary initial conditions
b) Express P and p as functions of only q Q m ω and τ You may want first to express Q and P as the functions of q and p and then rearrange equations Note that there should be no time dependence in these expressions
c) Integrate p as a function of q to obtain q-dependence of F Remember to include the undetermined integrating constant(q) C(Q)
d) Use equation for P (Q q) to find C(Q) and determine F (Q q)
e) Verify that F (Q q) is the correct generating function
5
Problem 2 Scattering from a rotationally symmetric surface (30 points)
Consider small particles moving with velocity parallel to the z-axis Particles are scattering from a perfectly elastic and frictionless surface The surface is rotationally symmetric about the z-axis and the shape of the surface is ρ(z) = z3 for z gt 0 We want to find differential scattering cross section σ(θ)
a) Find the relationship between the scattering angle θ and the impact parameter Note that the surface at the impact point can be considered as a perfectly elastic wall tangential to the curve at that point
b) Extract b(θ) and determine the differential cross section
c) Make a sketch of the scattering angle at some representative point ρ(z) for the case of the surface that is frictionless but totally inelastic
d) Make a sketch of the scattering angle at some representative point ρ(z) for the case of surface that is elastic but it has very high friction
6
Problem 3 Motion in rotating frame (35 points)
Consider a cannon located at geographical lattitude of exactly 45o North Cannon can fire identical projectiles in East North West and South directions All projectiles have identical initial speed of v0 = 200 ms and the cannon always points up at exactly 45o to the horizontal In your calculations of the projectile trajectory you can ignore the curvature of the Earth Assume that there is no air resistance
Assume that the radius of the Earth is R = 6 middot106 m and that the angular velocity of Earthrsquos rotation is Ω = 7 middot 10minus5 sminus1 Gravitational acceleration is g = 10 ms2 Do your calculations in the coordinate system where the z-axis is vertical pointing up with 0 at the center of the Earth the x-axis points North and the y-axis points West
a) Assume that the Earth is not rotating Obtain the algebraic formulas and the numericals value for the total range in meters maximum height above the ground in meters and the projectile flight time in seconds
b) Assume now that the Earth is rotating with its usual Ω Write down an expresshy
sion for acceleration ai = (ax ay az) in terms of components of r = (x y z) and Ω v = (x y˙ z) Ignore very small terms proportional to Ω2x Ω2y and replace radicz with R Keep all variables in algebraic form but replace sin 45o and cos 45o with 1 2
Note the following sections can be quite time consuming Start them only after you have finalized the other problems and sections in this quiz
c) The gun is being shot in the four geographical directions ENW S Write down the expressions for acceleration individually for each direction In each case remove the very small terms and find cancellations of terms of roughly equal size Justify your choices Note that some numerical cancellations are possible since the speed of the projectile happens to be very close to the linear speed of the Earthrsquos surface at that lattitude
d) Based on the magnitudes and signs of the terms of a obtained in c) estimate the effect of the earthrsquos rotation on the position of the impact parameter of the projectile for each of the four cases Mark the location of the new impact point as compared to no-rotation impact point (as obtained in a)) on graphs similar to Figure 1 The center of the graph corresponds to the no-rotation impact position Do not do the precise calculations try only to estimate the direction and relative magnitude of the deviation All four graphs should be oriented with North at the top and East to the right
7
x
yNorth
East
West
South
Figure 1 Impact Point Graph
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 8due Monday November 8 2006 at 1230 PM
Suggested Reading
Lecture Material Goldstein Sections 49 410 53 and 54 Also Chapter 10 Marion and Thronton
Problems
Problem 81 (25 pts)
Goldstein Exercise 22 page 183
Problem 82 (25 pts)
Marion and Thornton 10-12
Problem 83 (25 pts)
Marion and Thornton 10-15
Problem 84 (25 pts)
Goldstein Exercise 17 page 235
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 9due Wednesday November 29 2006 at 1230 PM
Suggested Reading
Goldstein Chapter 5
Problems
Problem 91 (25 pts)
Goldstein Derivation 6 page 233 Ignore the last sentence of question c) (Poinsot construction)
Problem 92 (25 pts)
Goldstein Exercise 18 page 235
Problem 93 (25 pts)
Goldstein Exercise 20 page 236
Problem 94 (25 pts)
Goldstein Exercise 29 page 237
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 10due Wednesday December 6 2006 at 1230 PM
Suggested Reading
Goldstein Sections 15 85 and Chapter 13
Problems
Problem 101 (25 pts)
Goldstein Exercise 1 page 598
Problem 102 (25 pts)
Goldstein Exercise 3 page 599
Problem 103 (25 pts)
Goldstein Exercise 4 page 599
Problem 104 (25 pts)
Goldstein Exercise 12 page 600
1
Massachusetts Institute of Technology Department of Physics
Course 809 Classical Mechanics Term Fall 2006
Quiz 1 October 4 2006
Instructions
bull Do not start until you are told to do so
bull Solve all problems
bull Put your name on the covers of all notebooks you are using
bull Show all work neatly in the blue book label the problem you are working on
bull Mark the final answers
bull Books and notes are not to be used Calculators are unnecessary
2
Useful Formulae
Newton and Basic Kinematics
F = p = ma for v c t=t
v = v0 +
dta t=0
t=t =t
r = r0 + v0t +
dt t
dtF (t)m t=0 t =0
Lagrangian and Hamiltonian
L(q q) = T minus U H(p q) = T + U = pq minus L
Euler-Lagrange (without and with constraints)
partL d partL partL d partL partgaminus = 0 minus + λa = 0 partx dt partx partx dt partx partxa
Polar Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Cylindrical Coordinates
x = r cos φ y = r sin φ z = z
Possibly useful integrals
dx dx = arctan(x) = arctanh(x)
1 + x2 1 minus x2
3
Problem 1 Variable Length Pendulum (35 points)
Consider a simple pendulum consisting of mass m attached to a string of length L After the pendulum is set into motion (at t = 0) the length of the string is lenghtened at a constant rate
dL = α = constant
dt The suspension point remains fixed
a) How many degrees of freedom does the system have
b) Write the Lagrangian for the pendulum Calculate partL is it equal to zero partt
c) Write the equations of motion for the pendulum do not solve Show that the equations of motion become the equations of the fixed length pendulum for α = 0
d) Write the Hamiltonian for the system
e) Calculate the total mechanical energy of the system Compare to the Hamiltoshynian
f) The energy of the system is not conserved What is the rate of change Give physical interpretation of the sources and magnitude of power flowing in or out of the system
Problem 2 Particle on a rotating wire (35 points)
A particle of mass m is constrained to move along a straight frictionless wire The wire is rotating in a vertical plane at a constant angular velocity Ω as shown in the Figure 1 The system is in the gravitational field with gravitational acceleration g pointing downwards At t = 0 the mass was stationary with respect to the wire and it was at a distance R0 from the axis of rotation
a) Write the Lagrangian for a free mass constrained to the vertical plane in gravishytational field using polar coordinate system
b) Write explicitly the constraint equations that force the mass to remain on the rotating wire
c) Write equations of motion for all the coordinates introducing Lagrange Multiplishyers
4
m
g
R0 Ω
Figure 1 Particle on a rotating wire
d) Obtain the expressions for the forces of constraints Give the physical interpreshytation of these forces
e) For sufficiently large Ω the mass will be moving away from the rotation axis for all wire positions What is the minimum value of the angular velocity such that this is guaranteed
Problem 3 Double Pendulum (30 points)
Consider a system consisting of two masses m1 and m2 and connected with massless rigid rods of length L1 and L2 (see Figure 2) As the pendulum moves both masses remain in the vertical plane
L1
g
m 1
L 2
m 2
Figure 2 Double Pendulum
a) How many degrees of freedom does the system have
b) Write the Lagrangian for the system
c) Write equations of motion for the system Do not solve
Massachusetts Institute of Technology Department of Physics
Course 809 Classical Mechanics Term Fall 2006
Quiz 2 November 15 2006
Instructions
bull Do not start until you are told to do so
bull Solve all problems
bull Put your name on the covers of all notebooks you are using
bull Show all work neatly in the white book label the problem you are working on
bull Mark the final answers
bull Books and notes are not to be used You may use your calculator
2
Useful Formulae
Newton and Basic Kinematics
F = p = ma for v c t=t v = v0 + dtprimea
t=0 t=t t=t
r = r0 + v0t + dtprime dtprimeprimeF (tprimeprime)m t=0 t =0
Gravitational Law
F = minus Gm1m2
r122r12
Lagrangian and Hamiltonian
partqL(q q) = T minus U H(p q) = T + U = p minus L
partt
Hamilton Equation of Motion
partH partH = minusp = q
partq partp
Generating function
partF (Q q) partF (Q q) = p = minusP
partq partQ
Poisson Brackets
partg partf partg partf [g f ] = minus
partq partp partp partq
Euler-Lagrange (without and with constraints)
partL d partL partL d partL partgminus = 0 minus + λ = 0 partx dt partx partx dt partx partx
Polar Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Orbit Equation
micro 1 u primeprime + u = minus F (u) with u =
2u2 r
ε =
3
Effective Potential
2
V (r) = U(r) + 2micror2
Keplerian Orbits
k α U(r) = minus = ε cos θ + 1
r r
α = 2
ε = 1 +2E2
τ 2 =4π2micro
a 3
microk microk2 k α α
rmin = a(1 minus ε) = rmax = a(1 + ε) =1 + ε 1 minus ε
Spherical Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Inelastic Scattering (coefficient of restitution)
|v2 minus v1||u2 minus u1|
Scattering
dσ dσ b db σ(θ) = = =
dΩ dφ sin θdθ sin θ dθ sin θ π θ
tan ψ = ζ = minus cos θ + (m1m2) 2 2
Vector in fixed frame expressed in terms of vector in rotating frame and rotation velocity
dX dX( )inertial = ( )rotating + (ω times X )dt dt
Acceleration in accelerated and rotating frame
a = g minus V minus (ω times r) minus 2(ω times v) minus (ω times (ω times r))
Useful Trigonometrical Formulas
sin(A + B) = sin A cos B + cos A sin B
cos(A + B) = cos A cos B minus sin A sin B
4
Problem 1 Canonical Transformation (35 points)
Consider a harmonic oscillator with Hamiltonian
p2 mω2q2
H = + 2m 2
Introduce transformation of variables from q(t) and p(t) to Q(t) = q(t + τ) and P (t) = p(t + τ) where τ is constant The goal of this problem is to find generating function F (Q q) of this canonical transformation of variables
a) Solve Hamilton equations of motion and find q(t) and p(t) for arbitrary initial conditions
b) Express P and p as functions of only q Q m ω and τ You may want first to express Q and P as the functions of q and p and then rearrange equations Note that there should be no time dependence in these expressions
c) Integrate p as a function of q to obtain q-dependence of F Remember to include the undetermined integrating constant(q) C(Q)
d) Use equation for P (Q q) to find C(Q) and determine F (Q q)
e) Verify that F (Q q) is the correct generating function
5
Problem 2 Scattering from a rotationally symmetric surface (30 points)
Consider small particles moving with velocity parallel to the z-axis Particles are scattering from a perfectly elastic and frictionless surface The surface is rotationally symmetric about the z-axis and the shape of the surface is ρ(z) = z3 for z gt 0 We want to find differential scattering cross section σ(θ)
a) Find the relationship between the scattering angle θ and the impact parameter Note that the surface at the impact point can be considered as a perfectly elastic wall tangential to the curve at that point
b) Extract b(θ) and determine the differential cross section
c) Make a sketch of the scattering angle at some representative point ρ(z) for the case of the surface that is frictionless but totally inelastic
d) Make a sketch of the scattering angle at some representative point ρ(z) for the case of surface that is elastic but it has very high friction
6
Problem 3 Motion in rotating frame (35 points)
Consider a cannon located at geographical lattitude of exactly 45o North Cannon can fire identical projectiles in East North West and South directions All projectiles have identical initial speed of v0 = 200 ms and the cannon always points up at exactly 45o to the horizontal In your calculations of the projectile trajectory you can ignore the curvature of the Earth Assume that there is no air resistance
Assume that the radius of the Earth is R = 6 middot106 m and that the angular velocity of Earthrsquos rotation is Ω = 7 middot 10minus5 sminus1 Gravitational acceleration is g = 10 ms2 Do your calculations in the coordinate system where the z-axis is vertical pointing up with 0 at the center of the Earth the x-axis points North and the y-axis points West
a) Assume that the Earth is not rotating Obtain the algebraic formulas and the numericals value for the total range in meters maximum height above the ground in meters and the projectile flight time in seconds
b) Assume now that the Earth is rotating with its usual Ω Write down an expresshy
sion for acceleration ai = (ax ay az) in terms of components of r = (x y z) and Ω v = (x y˙ z) Ignore very small terms proportional to Ω2x Ω2y and replace radicz with R Keep all variables in algebraic form but replace sin 45o and cos 45o with 1 2
Note the following sections can be quite time consuming Start them only after you have finalized the other problems and sections in this quiz
c) The gun is being shot in the four geographical directions ENW S Write down the expressions for acceleration individually for each direction In each case remove the very small terms and find cancellations of terms of roughly equal size Justify your choices Note that some numerical cancellations are possible since the speed of the projectile happens to be very close to the linear speed of the Earthrsquos surface at that lattitude
d) Based on the magnitudes and signs of the terms of a obtained in c) estimate the effect of the earthrsquos rotation on the position of the impact parameter of the projectile for each of the four cases Mark the location of the new impact point as compared to no-rotation impact point (as obtained in a)) on graphs similar to Figure 1 The center of the graph corresponds to the no-rotation impact position Do not do the precise calculations try only to estimate the direction and relative magnitude of the deviation All four graphs should be oriented with North at the top and East to the right
7
x
yNorth
East
West
South
Figure 1 Impact Point Graph
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 9due Wednesday November 29 2006 at 1230 PM
Suggested Reading
Goldstein Chapter 5
Problems
Problem 91 (25 pts)
Goldstein Derivation 6 page 233 Ignore the last sentence of question c) (Poinsot construction)
Problem 92 (25 pts)
Goldstein Exercise 18 page 235
Problem 93 (25 pts)
Goldstein Exercise 20 page 236
Problem 94 (25 pts)
Goldstein Exercise 29 page 237
1
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 10due Wednesday December 6 2006 at 1230 PM
Suggested Reading
Goldstein Sections 15 85 and Chapter 13
Problems
Problem 101 (25 pts)
Goldstein Exercise 1 page 598
Problem 102 (25 pts)
Goldstein Exercise 3 page 599
Problem 103 (25 pts)
Goldstein Exercise 4 page 599
Problem 104 (25 pts)
Goldstein Exercise 12 page 600
1
Massachusetts Institute of Technology Department of Physics
Course 809 Classical Mechanics Term Fall 2006
Quiz 1 October 4 2006
Instructions
bull Do not start until you are told to do so
bull Solve all problems
bull Put your name on the covers of all notebooks you are using
bull Show all work neatly in the blue book label the problem you are working on
bull Mark the final answers
bull Books and notes are not to be used Calculators are unnecessary
2
Useful Formulae
Newton and Basic Kinematics
F = p = ma for v c t=t
v = v0 +
dta t=0
t=t =t
r = r0 + v0t +
dt t
dtF (t)m t=0 t =0
Lagrangian and Hamiltonian
L(q q) = T minus U H(p q) = T + U = pq minus L
Euler-Lagrange (without and with constraints)
partL d partL partL d partL partgaminus = 0 minus + λa = 0 partx dt partx partx dt partx partxa
Polar Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Cylindrical Coordinates
x = r cos φ y = r sin φ z = z
Possibly useful integrals
dx dx = arctan(x) = arctanh(x)
1 + x2 1 minus x2
3
Problem 1 Variable Length Pendulum (35 points)
Consider a simple pendulum consisting of mass m attached to a string of length L After the pendulum is set into motion (at t = 0) the length of the string is lenghtened at a constant rate
dL = α = constant
dt The suspension point remains fixed
a) How many degrees of freedom does the system have
b) Write the Lagrangian for the pendulum Calculate partL is it equal to zero partt
c) Write the equations of motion for the pendulum do not solve Show that the equations of motion become the equations of the fixed length pendulum for α = 0
d) Write the Hamiltonian for the system
e) Calculate the total mechanical energy of the system Compare to the Hamiltoshynian
f) The energy of the system is not conserved What is the rate of change Give physical interpretation of the sources and magnitude of power flowing in or out of the system
Problem 2 Particle on a rotating wire (35 points)
A particle of mass m is constrained to move along a straight frictionless wire The wire is rotating in a vertical plane at a constant angular velocity Ω as shown in the Figure 1 The system is in the gravitational field with gravitational acceleration g pointing downwards At t = 0 the mass was stationary with respect to the wire and it was at a distance R0 from the axis of rotation
a) Write the Lagrangian for a free mass constrained to the vertical plane in gravishytational field using polar coordinate system
b) Write explicitly the constraint equations that force the mass to remain on the rotating wire
c) Write equations of motion for all the coordinates introducing Lagrange Multiplishyers
4
m
g
R0 Ω
Figure 1 Particle on a rotating wire
d) Obtain the expressions for the forces of constraints Give the physical interpreshytation of these forces
e) For sufficiently large Ω the mass will be moving away from the rotation axis for all wire positions What is the minimum value of the angular velocity such that this is guaranteed
Problem 3 Double Pendulum (30 points)
Consider a system consisting of two masses m1 and m2 and connected with massless rigid rods of length L1 and L2 (see Figure 2) As the pendulum moves both masses remain in the vertical plane
L1
g
m 1
L 2
m 2
Figure 2 Double Pendulum
a) How many degrees of freedom does the system have
b) Write the Lagrangian for the system
c) Write equations of motion for the system Do not solve
Massachusetts Institute of Technology Department of Physics
Course 809 Classical Mechanics Term Fall 2006
Quiz 2 November 15 2006
Instructions
bull Do not start until you are told to do so
bull Solve all problems
bull Put your name on the covers of all notebooks you are using
bull Show all work neatly in the white book label the problem you are working on
bull Mark the final answers
bull Books and notes are not to be used You may use your calculator
2
Useful Formulae
Newton and Basic Kinematics
F = p = ma for v c t=t v = v0 + dtprimea
t=0 t=t t=t
r = r0 + v0t + dtprime dtprimeprimeF (tprimeprime)m t=0 t =0
Gravitational Law
F = minus Gm1m2
r122r12
Lagrangian and Hamiltonian
partqL(q q) = T minus U H(p q) = T + U = p minus L
partt
Hamilton Equation of Motion
partH partH = minusp = q
partq partp
Generating function
partF (Q q) partF (Q q) = p = minusP
partq partQ
Poisson Brackets
partg partf partg partf [g f ] = minus
partq partp partp partq
Euler-Lagrange (without and with constraints)
partL d partL partL d partL partgminus = 0 minus + λ = 0 partx dt partx partx dt partx partx
Polar Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Orbit Equation
micro 1 u primeprime + u = minus F (u) with u =
2u2 r
ε =
3
Effective Potential
2
V (r) = U(r) + 2micror2
Keplerian Orbits
k α U(r) = minus = ε cos θ + 1
r r
α = 2
ε = 1 +2E2
τ 2 =4π2micro
a 3
microk microk2 k α α
rmin = a(1 minus ε) = rmax = a(1 + ε) =1 + ε 1 minus ε
Spherical Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Inelastic Scattering (coefficient of restitution)
|v2 minus v1||u2 minus u1|
Scattering
dσ dσ b db σ(θ) = = =
dΩ dφ sin θdθ sin θ dθ sin θ π θ
tan ψ = ζ = minus cos θ + (m1m2) 2 2
Vector in fixed frame expressed in terms of vector in rotating frame and rotation velocity
dX dX( )inertial = ( )rotating + (ω times X )dt dt
Acceleration in accelerated and rotating frame
a = g minus V minus (ω times r) minus 2(ω times v) minus (ω times (ω times r))
Useful Trigonometrical Formulas
sin(A + B) = sin A cos B + cos A sin B
cos(A + B) = cos A cos B minus sin A sin B
4
Problem 1 Canonical Transformation (35 points)
Consider a harmonic oscillator with Hamiltonian
p2 mω2q2
H = + 2m 2
Introduce transformation of variables from q(t) and p(t) to Q(t) = q(t + τ) and P (t) = p(t + τ) where τ is constant The goal of this problem is to find generating function F (Q q) of this canonical transformation of variables
a) Solve Hamilton equations of motion and find q(t) and p(t) for arbitrary initial conditions
b) Express P and p as functions of only q Q m ω and τ You may want first to express Q and P as the functions of q and p and then rearrange equations Note that there should be no time dependence in these expressions
c) Integrate p as a function of q to obtain q-dependence of F Remember to include the undetermined integrating constant(q) C(Q)
d) Use equation for P (Q q) to find C(Q) and determine F (Q q)
e) Verify that F (Q q) is the correct generating function
5
Problem 2 Scattering from a rotationally symmetric surface (30 points)
Consider small particles moving with velocity parallel to the z-axis Particles are scattering from a perfectly elastic and frictionless surface The surface is rotationally symmetric about the z-axis and the shape of the surface is ρ(z) = z3 for z gt 0 We want to find differential scattering cross section σ(θ)
a) Find the relationship between the scattering angle θ and the impact parameter Note that the surface at the impact point can be considered as a perfectly elastic wall tangential to the curve at that point
b) Extract b(θ) and determine the differential cross section
c) Make a sketch of the scattering angle at some representative point ρ(z) for the case of the surface that is frictionless but totally inelastic
d) Make a sketch of the scattering angle at some representative point ρ(z) for the case of surface that is elastic but it has very high friction
6
Problem 3 Motion in rotating frame (35 points)
Consider a cannon located at geographical lattitude of exactly 45o North Cannon can fire identical projectiles in East North West and South directions All projectiles have identical initial speed of v0 = 200 ms and the cannon always points up at exactly 45o to the horizontal In your calculations of the projectile trajectory you can ignore the curvature of the Earth Assume that there is no air resistance
Assume that the radius of the Earth is R = 6 middot106 m and that the angular velocity of Earthrsquos rotation is Ω = 7 middot 10minus5 sminus1 Gravitational acceleration is g = 10 ms2 Do your calculations in the coordinate system where the z-axis is vertical pointing up with 0 at the center of the Earth the x-axis points North and the y-axis points West
a) Assume that the Earth is not rotating Obtain the algebraic formulas and the numericals value for the total range in meters maximum height above the ground in meters and the projectile flight time in seconds
b) Assume now that the Earth is rotating with its usual Ω Write down an expresshy
sion for acceleration ai = (ax ay az) in terms of components of r = (x y z) and Ω v = (x y˙ z) Ignore very small terms proportional to Ω2x Ω2y and replace radicz with R Keep all variables in algebraic form but replace sin 45o and cos 45o with 1 2
Note the following sections can be quite time consuming Start them only after you have finalized the other problems and sections in this quiz
c) The gun is being shot in the four geographical directions ENW S Write down the expressions for acceleration individually for each direction In each case remove the very small terms and find cancellations of terms of roughly equal size Justify your choices Note that some numerical cancellations are possible since the speed of the projectile happens to be very close to the linear speed of the Earthrsquos surface at that lattitude
d) Based on the magnitudes and signs of the terms of a obtained in c) estimate the effect of the earthrsquos rotation on the position of the impact parameter of the projectile for each of the four cases Mark the location of the new impact point as compared to no-rotation impact point (as obtained in a)) on graphs similar to Figure 1 The center of the graph corresponds to the no-rotation impact position Do not do the precise calculations try only to estimate the direction and relative magnitude of the deviation All four graphs should be oriented with North at the top and East to the right
7
x
yNorth
East
West
South
Figure 1 Impact Point Graph
Massachusetts Institute of Technology Physics 809 Fall 2006
Homework 10due Wednesday December 6 2006 at 1230 PM
Suggested Reading
Goldstein Sections 15 85 and Chapter 13
Problems
Problem 101 (25 pts)
Goldstein Exercise 1 page 598
Problem 102 (25 pts)
Goldstein Exercise 3 page 599
Problem 103 (25 pts)
Goldstein Exercise 4 page 599
Problem 104 (25 pts)
Goldstein Exercise 12 page 600
1
Massachusetts Institute of Technology Department of Physics
Course 809 Classical Mechanics Term Fall 2006
Quiz 1 October 4 2006
Instructions
bull Do not start until you are told to do so
bull Solve all problems
bull Put your name on the covers of all notebooks you are using
bull Show all work neatly in the blue book label the problem you are working on
bull Mark the final answers
bull Books and notes are not to be used Calculators are unnecessary
2
Useful Formulae
Newton and Basic Kinematics
F = p = ma for v c t=t
v = v0 +
dta t=0
t=t =t
r = r0 + v0t +
dt t
dtF (t)m t=0 t =0
Lagrangian and Hamiltonian
L(q q) = T minus U H(p q) = T + U = pq minus L
Euler-Lagrange (without and with constraints)
partL d partL partL d partL partgaminus = 0 minus + λa = 0 partx dt partx partx dt partx partxa
Polar Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Cylindrical Coordinates
x = r cos φ y = r sin φ z = z
Possibly useful integrals
dx dx = arctan(x) = arctanh(x)
1 + x2 1 minus x2
3
Problem 1 Variable Length Pendulum (35 points)
Consider a simple pendulum consisting of mass m attached to a string of length L After the pendulum is set into motion (at t = 0) the length of the string is lenghtened at a constant rate
dL = α = constant
dt The suspension point remains fixed
a) How many degrees of freedom does the system have
b) Write the Lagrangian for the pendulum Calculate partL is it equal to zero partt
c) Write the equations of motion for the pendulum do not solve Show that the equations of motion become the equations of the fixed length pendulum for α = 0
d) Write the Hamiltonian for the system
e) Calculate the total mechanical energy of the system Compare to the Hamiltoshynian
f) The energy of the system is not conserved What is the rate of change Give physical interpretation of the sources and magnitude of power flowing in or out of the system
Problem 2 Particle on a rotating wire (35 points)
A particle of mass m is constrained to move along a straight frictionless wire The wire is rotating in a vertical plane at a constant angular velocity Ω as shown in the Figure 1 The system is in the gravitational field with gravitational acceleration g pointing downwards At t = 0 the mass was stationary with respect to the wire and it was at a distance R0 from the axis of rotation
a) Write the Lagrangian for a free mass constrained to the vertical plane in gravishytational field using polar coordinate system
b) Write explicitly the constraint equations that force the mass to remain on the rotating wire
c) Write equations of motion for all the coordinates introducing Lagrange Multiplishyers
4
m
g
R0 Ω
Figure 1 Particle on a rotating wire
d) Obtain the expressions for the forces of constraints Give the physical interpreshytation of these forces
e) For sufficiently large Ω the mass will be moving away from the rotation axis for all wire positions What is the minimum value of the angular velocity such that this is guaranteed
Problem 3 Double Pendulum (30 points)
Consider a system consisting of two masses m1 and m2 and connected with massless rigid rods of length L1 and L2 (see Figure 2) As the pendulum moves both masses remain in the vertical plane
L1
g
m 1
L 2
m 2
Figure 2 Double Pendulum
a) How many degrees of freedom does the system have
b) Write the Lagrangian for the system
c) Write equations of motion for the system Do not solve
Massachusetts Institute of Technology Department of Physics
Course 809 Classical Mechanics Term Fall 2006
Quiz 2 November 15 2006
Instructions
bull Do not start until you are told to do so
bull Solve all problems
bull Put your name on the covers of all notebooks you are using
bull Show all work neatly in the white book label the problem you are working on
bull Mark the final answers
bull Books and notes are not to be used You may use your calculator
2
Useful Formulae
Newton and Basic Kinematics
F = p = ma for v c t=t v = v0 + dtprimea
t=0 t=t t=t
r = r0 + v0t + dtprime dtprimeprimeF (tprimeprime)m t=0 t =0
Gravitational Law
F = minus Gm1m2
r122r12
Lagrangian and Hamiltonian
partqL(q q) = T minus U H(p q) = T + U = p minus L
partt
Hamilton Equation of Motion
partH partH = minusp = q
partq partp
Generating function
partF (Q q) partF (Q q) = p = minusP
partq partQ
Poisson Brackets
partg partf partg partf [g f ] = minus
partq partp partp partq
Euler-Lagrange (without and with constraints)
partL d partL partL d partL partgminus = 0 minus + λ = 0 partx dt partx partx dt partx partx
Polar Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Orbit Equation
micro 1 u primeprime + u = minus F (u) with u =
2u2 r
ε =
3
Effective Potential
2
V (r) = U(r) + 2micror2
Keplerian Orbits
k α U(r) = minus = ε cos θ + 1
r r
α = 2
ε = 1 +2E2
τ 2 =4π2micro
a 3
microk microk2 k α α
rmin = a(1 minus ε) = rmax = a(1 + ε) =1 + ε 1 minus ε
Spherical Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Inelastic Scattering (coefficient of restitution)
|v2 minus v1||u2 minus u1|
Scattering
dσ dσ b db σ(θ) = = =
dΩ dφ sin θdθ sin θ dθ sin θ π θ
tan ψ = ζ = minus cos θ + (m1m2) 2 2
Vector in fixed frame expressed in terms of vector in rotating frame and rotation velocity
dX dX( )inertial = ( )rotating + (ω times X )dt dt
Acceleration in accelerated and rotating frame
a = g minus V minus (ω times r) minus 2(ω times v) minus (ω times (ω times r))
Useful Trigonometrical Formulas
sin(A + B) = sin A cos B + cos A sin B
cos(A + B) = cos A cos B minus sin A sin B
4
Problem 1 Canonical Transformation (35 points)
Consider a harmonic oscillator with Hamiltonian
p2 mω2q2
H = + 2m 2
Introduce transformation of variables from q(t) and p(t) to Q(t) = q(t + τ) and P (t) = p(t + τ) where τ is constant The goal of this problem is to find generating function F (Q q) of this canonical transformation of variables
a) Solve Hamilton equations of motion and find q(t) and p(t) for arbitrary initial conditions
b) Express P and p as functions of only q Q m ω and τ You may want first to express Q and P as the functions of q and p and then rearrange equations Note that there should be no time dependence in these expressions
c) Integrate p as a function of q to obtain q-dependence of F Remember to include the undetermined integrating constant(q) C(Q)
d) Use equation for P (Q q) to find C(Q) and determine F (Q q)
e) Verify that F (Q q) is the correct generating function
5
Problem 2 Scattering from a rotationally symmetric surface (30 points)
Consider small particles moving with velocity parallel to the z-axis Particles are scattering from a perfectly elastic and frictionless surface The surface is rotationally symmetric about the z-axis and the shape of the surface is ρ(z) = z3 for z gt 0 We want to find differential scattering cross section σ(θ)
a) Find the relationship between the scattering angle θ and the impact parameter Note that the surface at the impact point can be considered as a perfectly elastic wall tangential to the curve at that point
b) Extract b(θ) and determine the differential cross section
c) Make a sketch of the scattering angle at some representative point ρ(z) for the case of the surface that is frictionless but totally inelastic
d) Make a sketch of the scattering angle at some representative point ρ(z) for the case of surface that is elastic but it has very high friction
6
Problem 3 Motion in rotating frame (35 points)
Consider a cannon located at geographical lattitude of exactly 45o North Cannon can fire identical projectiles in East North West and South directions All projectiles have identical initial speed of v0 = 200 ms and the cannon always points up at exactly 45o to the horizontal In your calculations of the projectile trajectory you can ignore the curvature of the Earth Assume that there is no air resistance
Assume that the radius of the Earth is R = 6 middot106 m and that the angular velocity of Earthrsquos rotation is Ω = 7 middot 10minus5 sminus1 Gravitational acceleration is g = 10 ms2 Do your calculations in the coordinate system where the z-axis is vertical pointing up with 0 at the center of the Earth the x-axis points North and the y-axis points West
a) Assume that the Earth is not rotating Obtain the algebraic formulas and the numericals value for the total range in meters maximum height above the ground in meters and the projectile flight time in seconds
b) Assume now that the Earth is rotating with its usual Ω Write down an expresshy
sion for acceleration ai = (ax ay az) in terms of components of r = (x y z) and Ω v = (x y˙ z) Ignore very small terms proportional to Ω2x Ω2y and replace radicz with R Keep all variables in algebraic form but replace sin 45o and cos 45o with 1 2
Note the following sections can be quite time consuming Start them only after you have finalized the other problems and sections in this quiz
c) The gun is being shot in the four geographical directions ENW S Write down the expressions for acceleration individually for each direction In each case remove the very small terms and find cancellations of terms of roughly equal size Justify your choices Note that some numerical cancellations are possible since the speed of the projectile happens to be very close to the linear speed of the Earthrsquos surface at that lattitude
d) Based on the magnitudes and signs of the terms of a obtained in c) estimate the effect of the earthrsquos rotation on the position of the impact parameter of the projectile for each of the four cases Mark the location of the new impact point as compared to no-rotation impact point (as obtained in a)) on graphs similar to Figure 1 The center of the graph corresponds to the no-rotation impact position Do not do the precise calculations try only to estimate the direction and relative magnitude of the deviation All four graphs should be oriented with North at the top and East to the right
7
x
yNorth
East
West
South
Figure 1 Impact Point Graph
Massachusetts Institute of Technology Department of Physics
Course 809 Classical Mechanics Term Fall 2006
Quiz 1 October 4 2006
Instructions
bull Do not start until you are told to do so
bull Solve all problems
bull Put your name on the covers of all notebooks you are using
bull Show all work neatly in the blue book label the problem you are working on
bull Mark the final answers
bull Books and notes are not to be used Calculators are unnecessary
2
Useful Formulae
Newton and Basic Kinematics
F = p = ma for v c t=t
v = v0 +
dta t=0
t=t =t
r = r0 + v0t +
dt t
dtF (t)m t=0 t =0
Lagrangian and Hamiltonian
L(q q) = T minus U H(p q) = T + U = pq minus L
Euler-Lagrange (without and with constraints)
partL d partL partL d partL partgaminus = 0 minus + λa = 0 partx dt partx partx dt partx partxa
Polar Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Cylindrical Coordinates
x = r cos φ y = r sin φ z = z
Possibly useful integrals
dx dx = arctan(x) = arctanh(x)
1 + x2 1 minus x2
3
Problem 1 Variable Length Pendulum (35 points)
Consider a simple pendulum consisting of mass m attached to a string of length L After the pendulum is set into motion (at t = 0) the length of the string is lenghtened at a constant rate
dL = α = constant
dt The suspension point remains fixed
a) How many degrees of freedom does the system have
b) Write the Lagrangian for the pendulum Calculate partL is it equal to zero partt
c) Write the equations of motion for the pendulum do not solve Show that the equations of motion become the equations of the fixed length pendulum for α = 0
d) Write the Hamiltonian for the system
e) Calculate the total mechanical energy of the system Compare to the Hamiltoshynian
f) The energy of the system is not conserved What is the rate of change Give physical interpretation of the sources and magnitude of power flowing in or out of the system
Problem 2 Particle on a rotating wire (35 points)
A particle of mass m is constrained to move along a straight frictionless wire The wire is rotating in a vertical plane at a constant angular velocity Ω as shown in the Figure 1 The system is in the gravitational field with gravitational acceleration g pointing downwards At t = 0 the mass was stationary with respect to the wire and it was at a distance R0 from the axis of rotation
a) Write the Lagrangian for a free mass constrained to the vertical plane in gravishytational field using polar coordinate system
b) Write explicitly the constraint equations that force the mass to remain on the rotating wire
c) Write equations of motion for all the coordinates introducing Lagrange Multiplishyers
4
m
g
R0 Ω
Figure 1 Particle on a rotating wire
d) Obtain the expressions for the forces of constraints Give the physical interpreshytation of these forces
e) For sufficiently large Ω the mass will be moving away from the rotation axis for all wire positions What is the minimum value of the angular velocity such that this is guaranteed
Problem 3 Double Pendulum (30 points)
Consider a system consisting of two masses m1 and m2 and connected with massless rigid rods of length L1 and L2 (see Figure 2) As the pendulum moves both masses remain in the vertical plane
L1
g
m 1
L 2
m 2
Figure 2 Double Pendulum
a) How many degrees of freedom does the system have
b) Write the Lagrangian for the system
c) Write equations of motion for the system Do not solve
Massachusetts Institute of Technology Department of Physics
Course 809 Classical Mechanics Term Fall 2006
Quiz 2 November 15 2006
Instructions
bull Do not start until you are told to do so
bull Solve all problems
bull Put your name on the covers of all notebooks you are using
bull Show all work neatly in the white book label the problem you are working on
bull Mark the final answers
bull Books and notes are not to be used You may use your calculator
2
Useful Formulae
Newton and Basic Kinematics
F = p = ma for v c t=t v = v0 + dtprimea
t=0 t=t t=t
r = r0 + v0t + dtprime dtprimeprimeF (tprimeprime)m t=0 t =0
Gravitational Law
F = minus Gm1m2
r122r12
Lagrangian and Hamiltonian
partqL(q q) = T minus U H(p q) = T + U = p minus L
partt
Hamilton Equation of Motion
partH partH = minusp = q
partq partp
Generating function
partF (Q q) partF (Q q) = p = minusP
partq partQ
Poisson Brackets
partg partf partg partf [g f ] = minus
partq partp partp partq
Euler-Lagrange (without and with constraints)
partL d partL partL d partL partgminus = 0 minus + λ = 0 partx dt partx partx dt partx partx
Polar Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Orbit Equation
micro 1 u primeprime + u = minus F (u) with u =
2u2 r
ε =
3
Effective Potential
2
V (r) = U(r) + 2micror2
Keplerian Orbits
k α U(r) = minus = ε cos θ + 1
r r
α = 2
ε = 1 +2E2
τ 2 =4π2micro
a 3
microk microk2 k α α
rmin = a(1 minus ε) = rmax = a(1 + ε) =1 + ε 1 minus ε
Spherical Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Inelastic Scattering (coefficient of restitution)
|v2 minus v1||u2 minus u1|
Scattering
dσ dσ b db σ(θ) = = =
dΩ dφ sin θdθ sin θ dθ sin θ π θ
tan ψ = ζ = minus cos θ + (m1m2) 2 2
Vector in fixed frame expressed in terms of vector in rotating frame and rotation velocity
dX dX( )inertial = ( )rotating + (ω times X )dt dt
Acceleration in accelerated and rotating frame
a = g minus V minus (ω times r) minus 2(ω times v) minus (ω times (ω times r))
Useful Trigonometrical Formulas
sin(A + B) = sin A cos B + cos A sin B
cos(A + B) = cos A cos B minus sin A sin B
4
Problem 1 Canonical Transformation (35 points)
Consider a harmonic oscillator with Hamiltonian
p2 mω2q2
H = + 2m 2
Introduce transformation of variables from q(t) and p(t) to Q(t) = q(t + τ) and P (t) = p(t + τ) where τ is constant The goal of this problem is to find generating function F (Q q) of this canonical transformation of variables
a) Solve Hamilton equations of motion and find q(t) and p(t) for arbitrary initial conditions
b) Express P and p as functions of only q Q m ω and τ You may want first to express Q and P as the functions of q and p and then rearrange equations Note that there should be no time dependence in these expressions
c) Integrate p as a function of q to obtain q-dependence of F Remember to include the undetermined integrating constant(q) C(Q)
d) Use equation for P (Q q) to find C(Q) and determine F (Q q)
e) Verify that F (Q q) is the correct generating function
5
Problem 2 Scattering from a rotationally symmetric surface (30 points)
Consider small particles moving with velocity parallel to the z-axis Particles are scattering from a perfectly elastic and frictionless surface The surface is rotationally symmetric about the z-axis and the shape of the surface is ρ(z) = z3 for z gt 0 We want to find differential scattering cross section σ(θ)
a) Find the relationship between the scattering angle θ and the impact parameter Note that the surface at the impact point can be considered as a perfectly elastic wall tangential to the curve at that point
b) Extract b(θ) and determine the differential cross section
c) Make a sketch of the scattering angle at some representative point ρ(z) for the case of the surface that is frictionless but totally inelastic
d) Make a sketch of the scattering angle at some representative point ρ(z) for the case of surface that is elastic but it has very high friction
6
Problem 3 Motion in rotating frame (35 points)
Consider a cannon located at geographical lattitude of exactly 45o North Cannon can fire identical projectiles in East North West and South directions All projectiles have identical initial speed of v0 = 200 ms and the cannon always points up at exactly 45o to the horizontal In your calculations of the projectile trajectory you can ignore the curvature of the Earth Assume that there is no air resistance
Assume that the radius of the Earth is R = 6 middot106 m and that the angular velocity of Earthrsquos rotation is Ω = 7 middot 10minus5 sminus1 Gravitational acceleration is g = 10 ms2 Do your calculations in the coordinate system where the z-axis is vertical pointing up with 0 at the center of the Earth the x-axis points North and the y-axis points West
a) Assume that the Earth is not rotating Obtain the algebraic formulas and the numericals value for the total range in meters maximum height above the ground in meters and the projectile flight time in seconds
b) Assume now that the Earth is rotating with its usual Ω Write down an expresshy
sion for acceleration ai = (ax ay az) in terms of components of r = (x y z) and Ω v = (x y˙ z) Ignore very small terms proportional to Ω2x Ω2y and replace radicz with R Keep all variables in algebraic form but replace sin 45o and cos 45o with 1 2
Note the following sections can be quite time consuming Start them only after you have finalized the other problems and sections in this quiz
c) The gun is being shot in the four geographical directions ENW S Write down the expressions for acceleration individually for each direction In each case remove the very small terms and find cancellations of terms of roughly equal size Justify your choices Note that some numerical cancellations are possible since the speed of the projectile happens to be very close to the linear speed of the Earthrsquos surface at that lattitude
d) Based on the magnitudes and signs of the terms of a obtained in c) estimate the effect of the earthrsquos rotation on the position of the impact parameter of the projectile for each of the four cases Mark the location of the new impact point as compared to no-rotation impact point (as obtained in a)) on graphs similar to Figure 1 The center of the graph corresponds to the no-rotation impact position Do not do the precise calculations try only to estimate the direction and relative magnitude of the deviation All four graphs should be oriented with North at the top and East to the right
7
x
yNorth
East
West
South
Figure 1 Impact Point Graph
2
Useful Formulae
Newton and Basic Kinematics
F = p = ma for v c t=t
v = v0 +
dta t=0
t=t =t
r = r0 + v0t +
dt t
dtF (t)m t=0 t =0
Lagrangian and Hamiltonian
L(q q) = T minus U H(p q) = T + U = pq minus L
Euler-Lagrange (without and with constraints)
partL d partL partL d partL partgaminus = 0 minus + λa = 0 partx dt partx partx dt partx partxa
Polar Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Cylindrical Coordinates
x = r cos φ y = r sin φ z = z
Possibly useful integrals
dx dx = arctan(x) = arctanh(x)
1 + x2 1 minus x2
3
Problem 1 Variable Length Pendulum (35 points)
Consider a simple pendulum consisting of mass m attached to a string of length L After the pendulum is set into motion (at t = 0) the length of the string is lenghtened at a constant rate
dL = α = constant
dt The suspension point remains fixed
a) How many degrees of freedom does the system have
b) Write the Lagrangian for the pendulum Calculate partL is it equal to zero partt
c) Write the equations of motion for the pendulum do not solve Show that the equations of motion become the equations of the fixed length pendulum for α = 0
d) Write the Hamiltonian for the system
e) Calculate the total mechanical energy of the system Compare to the Hamiltoshynian
f) The energy of the system is not conserved What is the rate of change Give physical interpretation of the sources and magnitude of power flowing in or out of the system
Problem 2 Particle on a rotating wire (35 points)
A particle of mass m is constrained to move along a straight frictionless wire The wire is rotating in a vertical plane at a constant angular velocity Ω as shown in the Figure 1 The system is in the gravitational field with gravitational acceleration g pointing downwards At t = 0 the mass was stationary with respect to the wire and it was at a distance R0 from the axis of rotation
a) Write the Lagrangian for a free mass constrained to the vertical plane in gravishytational field using polar coordinate system
b) Write explicitly the constraint equations that force the mass to remain on the rotating wire
c) Write equations of motion for all the coordinates introducing Lagrange Multiplishyers
4
m
g
R0 Ω
Figure 1 Particle on a rotating wire
d) Obtain the expressions for the forces of constraints Give the physical interpreshytation of these forces
e) For sufficiently large Ω the mass will be moving away from the rotation axis for all wire positions What is the minimum value of the angular velocity such that this is guaranteed
Problem 3 Double Pendulum (30 points)
Consider a system consisting of two masses m1 and m2 and connected with massless rigid rods of length L1 and L2 (see Figure 2) As the pendulum moves both masses remain in the vertical plane
L1
g
m 1
L 2
m 2
Figure 2 Double Pendulum
a) How many degrees of freedom does the system have
b) Write the Lagrangian for the system
c) Write equations of motion for the system Do not solve
Massachusetts Institute of Technology Department of Physics
Course 809 Classical Mechanics Term Fall 2006
Quiz 2 November 15 2006
Instructions
bull Do not start until you are told to do so
bull Solve all problems
bull Put your name on the covers of all notebooks you are using
bull Show all work neatly in the white book label the problem you are working on
bull Mark the final answers
bull Books and notes are not to be used You may use your calculator
2
Useful Formulae
Newton and Basic Kinematics
F = p = ma for v c t=t v = v0 + dtprimea
t=0 t=t t=t
r = r0 + v0t + dtprime dtprimeprimeF (tprimeprime)m t=0 t =0
Gravitational Law
F = minus Gm1m2
r122r12
Lagrangian and Hamiltonian
partqL(q q) = T minus U H(p q) = T + U = p minus L
partt
Hamilton Equation of Motion
partH partH = minusp = q
partq partp
Generating function
partF (Q q) partF (Q q) = p = minusP
partq partQ
Poisson Brackets
partg partf partg partf [g f ] = minus
partq partp partp partq
Euler-Lagrange (without and with constraints)
partL d partL partL d partL partgminus = 0 minus + λ = 0 partx dt partx partx dt partx partx
Polar Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Orbit Equation
micro 1 u primeprime + u = minus F (u) with u =
2u2 r
ε =
3
Effective Potential
2
V (r) = U(r) + 2micror2
Keplerian Orbits
k α U(r) = minus = ε cos θ + 1
r r
α = 2
ε = 1 +2E2
τ 2 =4π2micro
a 3
microk microk2 k α α
rmin = a(1 minus ε) = rmax = a(1 + ε) =1 + ε 1 minus ε
Spherical Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Inelastic Scattering (coefficient of restitution)
|v2 minus v1||u2 minus u1|
Scattering
dσ dσ b db σ(θ) = = =
dΩ dφ sin θdθ sin θ dθ sin θ π θ
tan ψ = ζ = minus cos θ + (m1m2) 2 2
Vector in fixed frame expressed in terms of vector in rotating frame and rotation velocity
dX dX( )inertial = ( )rotating + (ω times X )dt dt
Acceleration in accelerated and rotating frame
a = g minus V minus (ω times r) minus 2(ω times v) minus (ω times (ω times r))
Useful Trigonometrical Formulas
sin(A + B) = sin A cos B + cos A sin B
cos(A + B) = cos A cos B minus sin A sin B
4
Problem 1 Canonical Transformation (35 points)
Consider a harmonic oscillator with Hamiltonian
p2 mω2q2
H = + 2m 2
Introduce transformation of variables from q(t) and p(t) to Q(t) = q(t + τ) and P (t) = p(t + τ) where τ is constant The goal of this problem is to find generating function F (Q q) of this canonical transformation of variables
a) Solve Hamilton equations of motion and find q(t) and p(t) for arbitrary initial conditions
b) Express P and p as functions of only q Q m ω and τ You may want first to express Q and P as the functions of q and p and then rearrange equations Note that there should be no time dependence in these expressions
c) Integrate p as a function of q to obtain q-dependence of F Remember to include the undetermined integrating constant(q) C(Q)
d) Use equation for P (Q q) to find C(Q) and determine F (Q q)
e) Verify that F (Q q) is the correct generating function
5
Problem 2 Scattering from a rotationally symmetric surface (30 points)
Consider small particles moving with velocity parallel to the z-axis Particles are scattering from a perfectly elastic and frictionless surface The surface is rotationally symmetric about the z-axis and the shape of the surface is ρ(z) = z3 for z gt 0 We want to find differential scattering cross section σ(θ)
a) Find the relationship between the scattering angle θ and the impact parameter Note that the surface at the impact point can be considered as a perfectly elastic wall tangential to the curve at that point
b) Extract b(θ) and determine the differential cross section
c) Make a sketch of the scattering angle at some representative point ρ(z) for the case of the surface that is frictionless but totally inelastic
d) Make a sketch of the scattering angle at some representative point ρ(z) for the case of surface that is elastic but it has very high friction
6
Problem 3 Motion in rotating frame (35 points)
Consider a cannon located at geographical lattitude of exactly 45o North Cannon can fire identical projectiles in East North West and South directions All projectiles have identical initial speed of v0 = 200 ms and the cannon always points up at exactly 45o to the horizontal In your calculations of the projectile trajectory you can ignore the curvature of the Earth Assume that there is no air resistance
Assume that the radius of the Earth is R = 6 middot106 m and that the angular velocity of Earthrsquos rotation is Ω = 7 middot 10minus5 sminus1 Gravitational acceleration is g = 10 ms2 Do your calculations in the coordinate system where the z-axis is vertical pointing up with 0 at the center of the Earth the x-axis points North and the y-axis points West
a) Assume that the Earth is not rotating Obtain the algebraic formulas and the numericals value for the total range in meters maximum height above the ground in meters and the projectile flight time in seconds
b) Assume now that the Earth is rotating with its usual Ω Write down an expresshy
sion for acceleration ai = (ax ay az) in terms of components of r = (x y z) and Ω v = (x y˙ z) Ignore very small terms proportional to Ω2x Ω2y and replace radicz with R Keep all variables in algebraic form but replace sin 45o and cos 45o with 1 2
Note the following sections can be quite time consuming Start them only after you have finalized the other problems and sections in this quiz
c) The gun is being shot in the four geographical directions ENW S Write down the expressions for acceleration individually for each direction In each case remove the very small terms and find cancellations of terms of roughly equal size Justify your choices Note that some numerical cancellations are possible since the speed of the projectile happens to be very close to the linear speed of the Earthrsquos surface at that lattitude
d) Based on the magnitudes and signs of the terms of a obtained in c) estimate the effect of the earthrsquos rotation on the position of the impact parameter of the projectile for each of the four cases Mark the location of the new impact point as compared to no-rotation impact point (as obtained in a)) on graphs similar to Figure 1 The center of the graph corresponds to the no-rotation impact position Do not do the precise calculations try only to estimate the direction and relative magnitude of the deviation All four graphs should be oriented with North at the top and East to the right
7
x
yNorth
East
West
South
Figure 1 Impact Point Graph
3
Problem 1 Variable Length Pendulum (35 points)
Consider a simple pendulum consisting of mass m attached to a string of length L After the pendulum is set into motion (at t = 0) the length of the string is lenghtened at a constant rate
dL = α = constant
dt The suspension point remains fixed
a) How many degrees of freedom does the system have
b) Write the Lagrangian for the pendulum Calculate partL is it equal to zero partt
c) Write the equations of motion for the pendulum do not solve Show that the equations of motion become the equations of the fixed length pendulum for α = 0
d) Write the Hamiltonian for the system
e) Calculate the total mechanical energy of the system Compare to the Hamiltoshynian
f) The energy of the system is not conserved What is the rate of change Give physical interpretation of the sources and magnitude of power flowing in or out of the system
Problem 2 Particle on a rotating wire (35 points)
A particle of mass m is constrained to move along a straight frictionless wire The wire is rotating in a vertical plane at a constant angular velocity Ω as shown in the Figure 1 The system is in the gravitational field with gravitational acceleration g pointing downwards At t = 0 the mass was stationary with respect to the wire and it was at a distance R0 from the axis of rotation
a) Write the Lagrangian for a free mass constrained to the vertical plane in gravishytational field using polar coordinate system
b) Write explicitly the constraint equations that force the mass to remain on the rotating wire
c) Write equations of motion for all the coordinates introducing Lagrange Multiplishyers
4
m
g
R0 Ω
Figure 1 Particle on a rotating wire
d) Obtain the expressions for the forces of constraints Give the physical interpreshytation of these forces
e) For sufficiently large Ω the mass will be moving away from the rotation axis for all wire positions What is the minimum value of the angular velocity such that this is guaranteed
Problem 3 Double Pendulum (30 points)
Consider a system consisting of two masses m1 and m2 and connected with massless rigid rods of length L1 and L2 (see Figure 2) As the pendulum moves both masses remain in the vertical plane
L1
g
m 1
L 2
m 2
Figure 2 Double Pendulum
a) How many degrees of freedom does the system have
b) Write the Lagrangian for the system
c) Write equations of motion for the system Do not solve
Massachusetts Institute of Technology Department of Physics
Course 809 Classical Mechanics Term Fall 2006
Quiz 2 November 15 2006
Instructions
bull Do not start until you are told to do so
bull Solve all problems
bull Put your name on the covers of all notebooks you are using
bull Show all work neatly in the white book label the problem you are working on
bull Mark the final answers
bull Books and notes are not to be used You may use your calculator
2
Useful Formulae
Newton and Basic Kinematics
F = p = ma for v c t=t v = v0 + dtprimea
t=0 t=t t=t
r = r0 + v0t + dtprime dtprimeprimeF (tprimeprime)m t=0 t =0
Gravitational Law
F = minus Gm1m2
r122r12
Lagrangian and Hamiltonian
partqL(q q) = T minus U H(p q) = T + U = p minus L
partt
Hamilton Equation of Motion
partH partH = minusp = q
partq partp
Generating function
partF (Q q) partF (Q q) = p = minusP
partq partQ
Poisson Brackets
partg partf partg partf [g f ] = minus
partq partp partp partq
Euler-Lagrange (without and with constraints)
partL d partL partL d partL partgminus = 0 minus + λ = 0 partx dt partx partx dt partx partx
Polar Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Orbit Equation
micro 1 u primeprime + u = minus F (u) with u =
2u2 r
ε =
3
Effective Potential
2
V (r) = U(r) + 2micror2
Keplerian Orbits
k α U(r) = minus = ε cos θ + 1
r r
α = 2
ε = 1 +2E2
τ 2 =4π2micro
a 3
microk microk2 k α α
rmin = a(1 minus ε) = rmax = a(1 + ε) =1 + ε 1 minus ε
Spherical Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Inelastic Scattering (coefficient of restitution)
|v2 minus v1||u2 minus u1|
Scattering
dσ dσ b db σ(θ) = = =
dΩ dφ sin θdθ sin θ dθ sin θ π θ
tan ψ = ζ = minus cos θ + (m1m2) 2 2
Vector in fixed frame expressed in terms of vector in rotating frame and rotation velocity
dX dX( )inertial = ( )rotating + (ω times X )dt dt
Acceleration in accelerated and rotating frame
a = g minus V minus (ω times r) minus 2(ω times v) minus (ω times (ω times r))
Useful Trigonometrical Formulas
sin(A + B) = sin A cos B + cos A sin B
cos(A + B) = cos A cos B minus sin A sin B
4
Problem 1 Canonical Transformation (35 points)
Consider a harmonic oscillator with Hamiltonian
p2 mω2q2
H = + 2m 2
Introduce transformation of variables from q(t) and p(t) to Q(t) = q(t + τ) and P (t) = p(t + τ) where τ is constant The goal of this problem is to find generating function F (Q q) of this canonical transformation of variables
a) Solve Hamilton equations of motion and find q(t) and p(t) for arbitrary initial conditions
b) Express P and p as functions of only q Q m ω and τ You may want first to express Q and P as the functions of q and p and then rearrange equations Note that there should be no time dependence in these expressions
c) Integrate p as a function of q to obtain q-dependence of F Remember to include the undetermined integrating constant(q) C(Q)
d) Use equation for P (Q q) to find C(Q) and determine F (Q q)
e) Verify that F (Q q) is the correct generating function
5
Problem 2 Scattering from a rotationally symmetric surface (30 points)
Consider small particles moving with velocity parallel to the z-axis Particles are scattering from a perfectly elastic and frictionless surface The surface is rotationally symmetric about the z-axis and the shape of the surface is ρ(z) = z3 for z gt 0 We want to find differential scattering cross section σ(θ)
a) Find the relationship between the scattering angle θ and the impact parameter Note that the surface at the impact point can be considered as a perfectly elastic wall tangential to the curve at that point
b) Extract b(θ) and determine the differential cross section
c) Make a sketch of the scattering angle at some representative point ρ(z) for the case of the surface that is frictionless but totally inelastic
d) Make a sketch of the scattering angle at some representative point ρ(z) for the case of surface that is elastic but it has very high friction
6
Problem 3 Motion in rotating frame (35 points)
Consider a cannon located at geographical lattitude of exactly 45o North Cannon can fire identical projectiles in East North West and South directions All projectiles have identical initial speed of v0 = 200 ms and the cannon always points up at exactly 45o to the horizontal In your calculations of the projectile trajectory you can ignore the curvature of the Earth Assume that there is no air resistance
Assume that the radius of the Earth is R = 6 middot106 m and that the angular velocity of Earthrsquos rotation is Ω = 7 middot 10minus5 sminus1 Gravitational acceleration is g = 10 ms2 Do your calculations in the coordinate system where the z-axis is vertical pointing up with 0 at the center of the Earth the x-axis points North and the y-axis points West
a) Assume that the Earth is not rotating Obtain the algebraic formulas and the numericals value for the total range in meters maximum height above the ground in meters and the projectile flight time in seconds
b) Assume now that the Earth is rotating with its usual Ω Write down an expresshy
sion for acceleration ai = (ax ay az) in terms of components of r = (x y z) and Ω v = (x y˙ z) Ignore very small terms proportional to Ω2x Ω2y and replace radicz with R Keep all variables in algebraic form but replace sin 45o and cos 45o with 1 2
Note the following sections can be quite time consuming Start them only after you have finalized the other problems and sections in this quiz
c) The gun is being shot in the four geographical directions ENW S Write down the expressions for acceleration individually for each direction In each case remove the very small terms and find cancellations of terms of roughly equal size Justify your choices Note that some numerical cancellations are possible since the speed of the projectile happens to be very close to the linear speed of the Earthrsquos surface at that lattitude
d) Based on the magnitudes and signs of the terms of a obtained in c) estimate the effect of the earthrsquos rotation on the position of the impact parameter of the projectile for each of the four cases Mark the location of the new impact point as compared to no-rotation impact point (as obtained in a)) on graphs similar to Figure 1 The center of the graph corresponds to the no-rotation impact position Do not do the precise calculations try only to estimate the direction and relative magnitude of the deviation All four graphs should be oriented with North at the top and East to the right
7
x
yNorth
East
West
South
Figure 1 Impact Point Graph
4
m
g
R0 Ω
Figure 1 Particle on a rotating wire
d) Obtain the expressions for the forces of constraints Give the physical interpreshytation of these forces
e) For sufficiently large Ω the mass will be moving away from the rotation axis for all wire positions What is the minimum value of the angular velocity such that this is guaranteed
Problem 3 Double Pendulum (30 points)
Consider a system consisting of two masses m1 and m2 and connected with massless rigid rods of length L1 and L2 (see Figure 2) As the pendulum moves both masses remain in the vertical plane
L1
g
m 1
L 2
m 2
Figure 2 Double Pendulum
a) How many degrees of freedom does the system have
b) Write the Lagrangian for the system
c) Write equations of motion for the system Do not solve
Massachusetts Institute of Technology Department of Physics
Course 809 Classical Mechanics Term Fall 2006
Quiz 2 November 15 2006
Instructions
bull Do not start until you are told to do so
bull Solve all problems
bull Put your name on the covers of all notebooks you are using
bull Show all work neatly in the white book label the problem you are working on
bull Mark the final answers
bull Books and notes are not to be used You may use your calculator
2
Useful Formulae
Newton and Basic Kinematics
F = p = ma for v c t=t v = v0 + dtprimea
t=0 t=t t=t
r = r0 + v0t + dtprime dtprimeprimeF (tprimeprime)m t=0 t =0
Gravitational Law
F = minus Gm1m2
r122r12
Lagrangian and Hamiltonian
partqL(q q) = T minus U H(p q) = T + U = p minus L
partt
Hamilton Equation of Motion
partH partH = minusp = q
partq partp
Generating function
partF (Q q) partF (Q q) = p = minusP
partq partQ
Poisson Brackets
partg partf partg partf [g f ] = minus
partq partp partp partq
Euler-Lagrange (without and with constraints)
partL d partL partL d partL partgminus = 0 minus + λ = 0 partx dt partx partx dt partx partx
Polar Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Orbit Equation
micro 1 u primeprime + u = minus F (u) with u =
2u2 r
ε =
3
Effective Potential
2
V (r) = U(r) + 2micror2
Keplerian Orbits
k α U(r) = minus = ε cos θ + 1
r r
α = 2
ε = 1 +2E2
τ 2 =4π2micro
a 3
microk microk2 k α α
rmin = a(1 minus ε) = rmax = a(1 + ε) =1 + ε 1 minus ε
Spherical Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Inelastic Scattering (coefficient of restitution)
|v2 minus v1||u2 minus u1|
Scattering
dσ dσ b db σ(θ) = = =
dΩ dφ sin θdθ sin θ dθ sin θ π θ
tan ψ = ζ = minus cos θ + (m1m2) 2 2
Vector in fixed frame expressed in terms of vector in rotating frame and rotation velocity
dX dX( )inertial = ( )rotating + (ω times X )dt dt
Acceleration in accelerated and rotating frame
a = g minus V minus (ω times r) minus 2(ω times v) minus (ω times (ω times r))
Useful Trigonometrical Formulas
sin(A + B) = sin A cos B + cos A sin B
cos(A + B) = cos A cos B minus sin A sin B
4
Problem 1 Canonical Transformation (35 points)
Consider a harmonic oscillator with Hamiltonian
p2 mω2q2
H = + 2m 2
Introduce transformation of variables from q(t) and p(t) to Q(t) = q(t + τ) and P (t) = p(t + τ) where τ is constant The goal of this problem is to find generating function F (Q q) of this canonical transformation of variables
a) Solve Hamilton equations of motion and find q(t) and p(t) for arbitrary initial conditions
b) Express P and p as functions of only q Q m ω and τ You may want first to express Q and P as the functions of q and p and then rearrange equations Note that there should be no time dependence in these expressions
c) Integrate p as a function of q to obtain q-dependence of F Remember to include the undetermined integrating constant(q) C(Q)
d) Use equation for P (Q q) to find C(Q) and determine F (Q q)
e) Verify that F (Q q) is the correct generating function
5
Problem 2 Scattering from a rotationally symmetric surface (30 points)
Consider small particles moving with velocity parallel to the z-axis Particles are scattering from a perfectly elastic and frictionless surface The surface is rotationally symmetric about the z-axis and the shape of the surface is ρ(z) = z3 for z gt 0 We want to find differential scattering cross section σ(θ)
a) Find the relationship between the scattering angle θ and the impact parameter Note that the surface at the impact point can be considered as a perfectly elastic wall tangential to the curve at that point
b) Extract b(θ) and determine the differential cross section
c) Make a sketch of the scattering angle at some representative point ρ(z) for the case of the surface that is frictionless but totally inelastic
d) Make a sketch of the scattering angle at some representative point ρ(z) for the case of surface that is elastic but it has very high friction
6
Problem 3 Motion in rotating frame (35 points)
Consider a cannon located at geographical lattitude of exactly 45o North Cannon can fire identical projectiles in East North West and South directions All projectiles have identical initial speed of v0 = 200 ms and the cannon always points up at exactly 45o to the horizontal In your calculations of the projectile trajectory you can ignore the curvature of the Earth Assume that there is no air resistance
Assume that the radius of the Earth is R = 6 middot106 m and that the angular velocity of Earthrsquos rotation is Ω = 7 middot 10minus5 sminus1 Gravitational acceleration is g = 10 ms2 Do your calculations in the coordinate system where the z-axis is vertical pointing up with 0 at the center of the Earth the x-axis points North and the y-axis points West
a) Assume that the Earth is not rotating Obtain the algebraic formulas and the numericals value for the total range in meters maximum height above the ground in meters and the projectile flight time in seconds
b) Assume now that the Earth is rotating with its usual Ω Write down an expresshy
sion for acceleration ai = (ax ay az) in terms of components of r = (x y z) and Ω v = (x y˙ z) Ignore very small terms proportional to Ω2x Ω2y and replace radicz with R Keep all variables in algebraic form but replace sin 45o and cos 45o with 1 2
Note the following sections can be quite time consuming Start them only after you have finalized the other problems and sections in this quiz
c) The gun is being shot in the four geographical directions ENW S Write down the expressions for acceleration individually for each direction In each case remove the very small terms and find cancellations of terms of roughly equal size Justify your choices Note that some numerical cancellations are possible since the speed of the projectile happens to be very close to the linear speed of the Earthrsquos surface at that lattitude
d) Based on the magnitudes and signs of the terms of a obtained in c) estimate the effect of the earthrsquos rotation on the position of the impact parameter of the projectile for each of the four cases Mark the location of the new impact point as compared to no-rotation impact point (as obtained in a)) on graphs similar to Figure 1 The center of the graph corresponds to the no-rotation impact position Do not do the precise calculations try only to estimate the direction and relative magnitude of the deviation All four graphs should be oriented with North at the top and East to the right
7
x
yNorth
East
West
South
Figure 1 Impact Point Graph
Massachusetts Institute of Technology Department of Physics
Course 809 Classical Mechanics Term Fall 2006
Quiz 2 November 15 2006
Instructions
bull Do not start until you are told to do so
bull Solve all problems
bull Put your name on the covers of all notebooks you are using
bull Show all work neatly in the white book label the problem you are working on
bull Mark the final answers
bull Books and notes are not to be used You may use your calculator
2
Useful Formulae
Newton and Basic Kinematics
F = p = ma for v c t=t v = v0 + dtprimea
t=0 t=t t=t
r = r0 + v0t + dtprime dtprimeprimeF (tprimeprime)m t=0 t =0
Gravitational Law
F = minus Gm1m2
r122r12
Lagrangian and Hamiltonian
partqL(q q) = T minus U H(p q) = T + U = p minus L
partt
Hamilton Equation of Motion
partH partH = minusp = q
partq partp
Generating function
partF (Q q) partF (Q q) = p = minusP
partq partQ
Poisson Brackets
partg partf partg partf [g f ] = minus
partq partp partp partq
Euler-Lagrange (without and with constraints)
partL d partL partL d partL partgminus = 0 minus + λ = 0 partx dt partx partx dt partx partx
Polar Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Orbit Equation
micro 1 u primeprime + u = minus F (u) with u =
2u2 r
ε =
3
Effective Potential
2
V (r) = U(r) + 2micror2
Keplerian Orbits
k α U(r) = minus = ε cos θ + 1
r r
α = 2
ε = 1 +2E2
τ 2 =4π2micro
a 3
microk microk2 k α α
rmin = a(1 minus ε) = rmax = a(1 + ε) =1 + ε 1 minus ε
Spherical Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Inelastic Scattering (coefficient of restitution)
|v2 minus v1||u2 minus u1|
Scattering
dσ dσ b db σ(θ) = = =
dΩ dφ sin θdθ sin θ dθ sin θ π θ
tan ψ = ζ = minus cos θ + (m1m2) 2 2
Vector in fixed frame expressed in terms of vector in rotating frame and rotation velocity
dX dX( )inertial = ( )rotating + (ω times X )dt dt
Acceleration in accelerated and rotating frame
a = g minus V minus (ω times r) minus 2(ω times v) minus (ω times (ω times r))
Useful Trigonometrical Formulas
sin(A + B) = sin A cos B + cos A sin B
cos(A + B) = cos A cos B minus sin A sin B
4
Problem 1 Canonical Transformation (35 points)
Consider a harmonic oscillator with Hamiltonian
p2 mω2q2
H = + 2m 2
Introduce transformation of variables from q(t) and p(t) to Q(t) = q(t + τ) and P (t) = p(t + τ) where τ is constant The goal of this problem is to find generating function F (Q q) of this canonical transformation of variables
a) Solve Hamilton equations of motion and find q(t) and p(t) for arbitrary initial conditions
b) Express P and p as functions of only q Q m ω and τ You may want first to express Q and P as the functions of q and p and then rearrange equations Note that there should be no time dependence in these expressions
c) Integrate p as a function of q to obtain q-dependence of F Remember to include the undetermined integrating constant(q) C(Q)
d) Use equation for P (Q q) to find C(Q) and determine F (Q q)
e) Verify that F (Q q) is the correct generating function
5
Problem 2 Scattering from a rotationally symmetric surface (30 points)
Consider small particles moving with velocity parallel to the z-axis Particles are scattering from a perfectly elastic and frictionless surface The surface is rotationally symmetric about the z-axis and the shape of the surface is ρ(z) = z3 for z gt 0 We want to find differential scattering cross section σ(θ)
a) Find the relationship between the scattering angle θ and the impact parameter Note that the surface at the impact point can be considered as a perfectly elastic wall tangential to the curve at that point
b) Extract b(θ) and determine the differential cross section
c) Make a sketch of the scattering angle at some representative point ρ(z) for the case of the surface that is frictionless but totally inelastic
d) Make a sketch of the scattering angle at some representative point ρ(z) for the case of surface that is elastic but it has very high friction
6
Problem 3 Motion in rotating frame (35 points)
Consider a cannon located at geographical lattitude of exactly 45o North Cannon can fire identical projectiles in East North West and South directions All projectiles have identical initial speed of v0 = 200 ms and the cannon always points up at exactly 45o to the horizontal In your calculations of the projectile trajectory you can ignore the curvature of the Earth Assume that there is no air resistance
Assume that the radius of the Earth is R = 6 middot106 m and that the angular velocity of Earthrsquos rotation is Ω = 7 middot 10minus5 sminus1 Gravitational acceleration is g = 10 ms2 Do your calculations in the coordinate system where the z-axis is vertical pointing up with 0 at the center of the Earth the x-axis points North and the y-axis points West
a) Assume that the Earth is not rotating Obtain the algebraic formulas and the numericals value for the total range in meters maximum height above the ground in meters and the projectile flight time in seconds
b) Assume now that the Earth is rotating with its usual Ω Write down an expresshy
sion for acceleration ai = (ax ay az) in terms of components of r = (x y z) and Ω v = (x y˙ z) Ignore very small terms proportional to Ω2x Ω2y and replace radicz with R Keep all variables in algebraic form but replace sin 45o and cos 45o with 1 2
Note the following sections can be quite time consuming Start them only after you have finalized the other problems and sections in this quiz
c) The gun is being shot in the four geographical directions ENW S Write down the expressions for acceleration individually for each direction In each case remove the very small terms and find cancellations of terms of roughly equal size Justify your choices Note that some numerical cancellations are possible since the speed of the projectile happens to be very close to the linear speed of the Earthrsquos surface at that lattitude
d) Based on the magnitudes and signs of the terms of a obtained in c) estimate the effect of the earthrsquos rotation on the position of the impact parameter of the projectile for each of the four cases Mark the location of the new impact point as compared to no-rotation impact point (as obtained in a)) on graphs similar to Figure 1 The center of the graph corresponds to the no-rotation impact position Do not do the precise calculations try only to estimate the direction and relative magnitude of the deviation All four graphs should be oriented with North at the top and East to the right
7
x
yNorth
East
West
South
Figure 1 Impact Point Graph
2
Useful Formulae
Newton and Basic Kinematics
F = p = ma for v c t=t v = v0 + dtprimea
t=0 t=t t=t
r = r0 + v0t + dtprime dtprimeprimeF (tprimeprime)m t=0 t =0
Gravitational Law
F = minus Gm1m2
r122r12
Lagrangian and Hamiltonian
partqL(q q) = T minus U H(p q) = T + U = p minus L
partt
Hamilton Equation of Motion
partH partH = minusp = q
partq partp
Generating function
partF (Q q) partF (Q q) = p = minusP
partq partQ
Poisson Brackets
partg partf partg partf [g f ] = minus
partq partp partp partq
Euler-Lagrange (without and with constraints)
partL d partL partL d partL partgminus = 0 minus + λ = 0 partx dt partx partx dt partx partx
Polar Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Orbit Equation
micro 1 u primeprime + u = minus F (u) with u =
2u2 r
ε =
3
Effective Potential
2
V (r) = U(r) + 2micror2
Keplerian Orbits
k α U(r) = minus = ε cos θ + 1
r r
α = 2
ε = 1 +2E2
τ 2 =4π2micro
a 3
microk microk2 k α α
rmin = a(1 minus ε) = rmax = a(1 + ε) =1 + ε 1 minus ε
Spherical Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Inelastic Scattering (coefficient of restitution)
|v2 minus v1||u2 minus u1|
Scattering
dσ dσ b db σ(θ) = = =
dΩ dφ sin θdθ sin θ dθ sin θ π θ
tan ψ = ζ = minus cos θ + (m1m2) 2 2
Vector in fixed frame expressed in terms of vector in rotating frame and rotation velocity
dX dX( )inertial = ( )rotating + (ω times X )dt dt
Acceleration in accelerated and rotating frame
a = g minus V minus (ω times r) minus 2(ω times v) minus (ω times (ω times r))
Useful Trigonometrical Formulas
sin(A + B) = sin A cos B + cos A sin B
cos(A + B) = cos A cos B minus sin A sin B
4
Problem 1 Canonical Transformation (35 points)
Consider a harmonic oscillator with Hamiltonian
p2 mω2q2
H = + 2m 2
Introduce transformation of variables from q(t) and p(t) to Q(t) = q(t + τ) and P (t) = p(t + τ) where τ is constant The goal of this problem is to find generating function F (Q q) of this canonical transformation of variables
a) Solve Hamilton equations of motion and find q(t) and p(t) for arbitrary initial conditions
b) Express P and p as functions of only q Q m ω and τ You may want first to express Q and P as the functions of q and p and then rearrange equations Note that there should be no time dependence in these expressions
c) Integrate p as a function of q to obtain q-dependence of F Remember to include the undetermined integrating constant(q) C(Q)
d) Use equation for P (Q q) to find C(Q) and determine F (Q q)
e) Verify that F (Q q) is the correct generating function
5
Problem 2 Scattering from a rotationally symmetric surface (30 points)
Consider small particles moving with velocity parallel to the z-axis Particles are scattering from a perfectly elastic and frictionless surface The surface is rotationally symmetric about the z-axis and the shape of the surface is ρ(z) = z3 for z gt 0 We want to find differential scattering cross section σ(θ)
a) Find the relationship between the scattering angle θ and the impact parameter Note that the surface at the impact point can be considered as a perfectly elastic wall tangential to the curve at that point
b) Extract b(θ) and determine the differential cross section
c) Make a sketch of the scattering angle at some representative point ρ(z) for the case of the surface that is frictionless but totally inelastic
d) Make a sketch of the scattering angle at some representative point ρ(z) for the case of surface that is elastic but it has very high friction
6
Problem 3 Motion in rotating frame (35 points)
Consider a cannon located at geographical lattitude of exactly 45o North Cannon can fire identical projectiles in East North West and South directions All projectiles have identical initial speed of v0 = 200 ms and the cannon always points up at exactly 45o to the horizontal In your calculations of the projectile trajectory you can ignore the curvature of the Earth Assume that there is no air resistance
Assume that the radius of the Earth is R = 6 middot106 m and that the angular velocity of Earthrsquos rotation is Ω = 7 middot 10minus5 sminus1 Gravitational acceleration is g = 10 ms2 Do your calculations in the coordinate system where the z-axis is vertical pointing up with 0 at the center of the Earth the x-axis points North and the y-axis points West
a) Assume that the Earth is not rotating Obtain the algebraic formulas and the numericals value for the total range in meters maximum height above the ground in meters and the projectile flight time in seconds
b) Assume now that the Earth is rotating with its usual Ω Write down an expresshy
sion for acceleration ai = (ax ay az) in terms of components of r = (x y z) and Ω v = (x y˙ z) Ignore very small terms proportional to Ω2x Ω2y and replace radicz with R Keep all variables in algebraic form but replace sin 45o and cos 45o with 1 2
Note the following sections can be quite time consuming Start them only after you have finalized the other problems and sections in this quiz
c) The gun is being shot in the four geographical directions ENW S Write down the expressions for acceleration individually for each direction In each case remove the very small terms and find cancellations of terms of roughly equal size Justify your choices Note that some numerical cancellations are possible since the speed of the projectile happens to be very close to the linear speed of the Earthrsquos surface at that lattitude
d) Based on the magnitudes and signs of the terms of a obtained in c) estimate the effect of the earthrsquos rotation on the position of the impact parameter of the projectile for each of the four cases Mark the location of the new impact point as compared to no-rotation impact point (as obtained in a)) on graphs similar to Figure 1 The center of the graph corresponds to the no-rotation impact position Do not do the precise calculations try only to estimate the direction and relative magnitude of the deviation All four graphs should be oriented with North at the top and East to the right
7
x
yNorth
East
West
South
Figure 1 Impact Point Graph
ε =
3
Effective Potential
2
V (r) = U(r) + 2micror2
Keplerian Orbits
k α U(r) = minus = ε cos θ + 1
r r
α = 2
ε = 1 +2E2
τ 2 =4π2micro
a 3
microk microk2 k α α
rmin = a(1 minus ε) = rmax = a(1 + ε) =1 + ε 1 minus ε
Spherical Coordinates
x = r sin θ cos φ y = r sin θ sin φ z = r cos θ
Inelastic Scattering (coefficient of restitution)
|v2 minus v1||u2 minus u1|
Scattering
dσ dσ b db σ(θ) = = =
dΩ dφ sin θdθ sin θ dθ sin θ π θ
tan ψ = ζ = minus cos θ + (m1m2) 2 2
Vector in fixed frame expressed in terms of vector in rotating frame and rotation velocity
dX dX( )inertial = ( )rotating + (ω times X )dt dt
Acceleration in accelerated and rotating frame
a = g minus V minus (ω times r) minus 2(ω times v) minus (ω times (ω times r))
Useful Trigonometrical Formulas
sin(A + B) = sin A cos B + cos A sin B
cos(A + B) = cos A cos B minus sin A sin B
4
Problem 1 Canonical Transformation (35 points)
Consider a harmonic oscillator with Hamiltonian
p2 mω2q2
H = + 2m 2
Introduce transformation of variables from q(t) and p(t) to Q(t) = q(t + τ) and P (t) = p(t + τ) where τ is constant The goal of this problem is to find generating function F (Q q) of this canonical transformation of variables
a) Solve Hamilton equations of motion and find q(t) and p(t) for arbitrary initial conditions
b) Express P and p as functions of only q Q m ω and τ You may want first to express Q and P as the functions of q and p and then rearrange equations Note that there should be no time dependence in these expressions
c) Integrate p as a function of q to obtain q-dependence of F Remember to include the undetermined integrating constant(q) C(Q)
d) Use equation for P (Q q) to find C(Q) and determine F (Q q)
e) Verify that F (Q q) is the correct generating function
5
Problem 2 Scattering from a rotationally symmetric surface (30 points)
Consider small particles moving with velocity parallel to the z-axis Particles are scattering from a perfectly elastic and frictionless surface The surface is rotationally symmetric about the z-axis and the shape of the surface is ρ(z) = z3 for z gt 0 We want to find differential scattering cross section σ(θ)
a) Find the relationship between the scattering angle θ and the impact parameter Note that the surface at the impact point can be considered as a perfectly elastic wall tangential to the curve at that point
b) Extract b(θ) and determine the differential cross section
c) Make a sketch of the scattering angle at some representative point ρ(z) for the case of the surface that is frictionless but totally inelastic
d) Make a sketch of the scattering angle at some representative point ρ(z) for the case of surface that is elastic but it has very high friction
6
Problem 3 Motion in rotating frame (35 points)
Consider a cannon located at geographical lattitude of exactly 45o North Cannon can fire identical projectiles in East North West and South directions All projectiles have identical initial speed of v0 = 200 ms and the cannon always points up at exactly 45o to the horizontal In your calculations of the projectile trajectory you can ignore the curvature of the Earth Assume that there is no air resistance
Assume that the radius of the Earth is R = 6 middot106 m and that the angular velocity of Earthrsquos rotation is Ω = 7 middot 10minus5 sminus1 Gravitational acceleration is g = 10 ms2 Do your calculations in the coordinate system where the z-axis is vertical pointing up with 0 at the center of the Earth the x-axis points North and the y-axis points West
a) Assume that the Earth is not rotating Obtain the algebraic formulas and the numericals value for the total range in meters maximum height above the ground in meters and the projectile flight time in seconds
b) Assume now that the Earth is rotating with its usual Ω Write down an expresshy
sion for acceleration ai = (ax ay az) in terms of components of r = (x y z) and Ω v = (x y˙ z) Ignore very small terms proportional to Ω2x Ω2y and replace radicz with R Keep all variables in algebraic form but replace sin 45o and cos 45o with 1 2
Note the following sections can be quite time consuming Start them only after you have finalized the other problems and sections in this quiz
c) The gun is being shot in the four geographical directions ENW S Write down the expressions for acceleration individually for each direction In each case remove the very small terms and find cancellations of terms of roughly equal size Justify your choices Note that some numerical cancellations are possible since the speed of the projectile happens to be very close to the linear speed of the Earthrsquos surface at that lattitude
d) Based on the magnitudes and signs of the terms of a obtained in c) estimate the effect of the earthrsquos rotation on the position of the impact parameter of the projectile for each of the four cases Mark the location of the new impact point as compared to no-rotation impact point (as obtained in a)) on graphs similar to Figure 1 The center of the graph corresponds to the no-rotation impact position Do not do the precise calculations try only to estimate the direction and relative magnitude of the deviation All four graphs should be oriented with North at the top and East to the right
7
x
yNorth
East
West
South
Figure 1 Impact Point Graph
4
Problem 1 Canonical Transformation (35 points)
Consider a harmonic oscillator with Hamiltonian
p2 mω2q2
H = + 2m 2
Introduce transformation of variables from q(t) and p(t) to Q(t) = q(t + τ) and P (t) = p(t + τ) where τ is constant The goal of this problem is to find generating function F (Q q) of this canonical transformation of variables
a) Solve Hamilton equations of motion and find q(t) and p(t) for arbitrary initial conditions
b) Express P and p as functions of only q Q m ω and τ You may want first to express Q and P as the functions of q and p and then rearrange equations Note that there should be no time dependence in these expressions
c) Integrate p as a function of q to obtain q-dependence of F Remember to include the undetermined integrating constant(q) C(Q)
d) Use equation for P (Q q) to find C(Q) and determine F (Q q)
e) Verify that F (Q q) is the correct generating function
5
Problem 2 Scattering from a rotationally symmetric surface (30 points)
Consider small particles moving with velocity parallel to the z-axis Particles are scattering from a perfectly elastic and frictionless surface The surface is rotationally symmetric about the z-axis and the shape of the surface is ρ(z) = z3 for z gt 0 We want to find differential scattering cross section σ(θ)
a) Find the relationship between the scattering angle θ and the impact parameter Note that the surface at the impact point can be considered as a perfectly elastic wall tangential to the curve at that point
b) Extract b(θ) and determine the differential cross section
c) Make a sketch of the scattering angle at some representative point ρ(z) for the case of the surface that is frictionless but totally inelastic
d) Make a sketch of the scattering angle at some representative point ρ(z) for the case of surface that is elastic but it has very high friction
6
Problem 3 Motion in rotating frame (35 points)
Consider a cannon located at geographical lattitude of exactly 45o North Cannon can fire identical projectiles in East North West and South directions All projectiles have identical initial speed of v0 = 200 ms and the cannon always points up at exactly 45o to the horizontal In your calculations of the projectile trajectory you can ignore the curvature of the Earth Assume that there is no air resistance
Assume that the radius of the Earth is R = 6 middot106 m and that the angular velocity of Earthrsquos rotation is Ω = 7 middot 10minus5 sminus1 Gravitational acceleration is g = 10 ms2 Do your calculations in the coordinate system where the z-axis is vertical pointing up with 0 at the center of the Earth the x-axis points North and the y-axis points West
a) Assume that the Earth is not rotating Obtain the algebraic formulas and the numericals value for the total range in meters maximum height above the ground in meters and the projectile flight time in seconds
b) Assume now that the Earth is rotating with its usual Ω Write down an expresshy
sion for acceleration ai = (ax ay az) in terms of components of r = (x y z) and Ω v = (x y˙ z) Ignore very small terms proportional to Ω2x Ω2y and replace radicz with R Keep all variables in algebraic form but replace sin 45o and cos 45o with 1 2
Note the following sections can be quite time consuming Start them only after you have finalized the other problems and sections in this quiz
c) The gun is being shot in the four geographical directions ENW S Write down the expressions for acceleration individually for each direction In each case remove the very small terms and find cancellations of terms of roughly equal size Justify your choices Note that some numerical cancellations are possible since the speed of the projectile happens to be very close to the linear speed of the Earthrsquos surface at that lattitude
d) Based on the magnitudes and signs of the terms of a obtained in c) estimate the effect of the earthrsquos rotation on the position of the impact parameter of the projectile for each of the four cases Mark the location of the new impact point as compared to no-rotation impact point (as obtained in a)) on graphs similar to Figure 1 The center of the graph corresponds to the no-rotation impact position Do not do the precise calculations try only to estimate the direction and relative magnitude of the deviation All four graphs should be oriented with North at the top and East to the right
7
x
yNorth
East
West
South
Figure 1 Impact Point Graph
5
Problem 2 Scattering from a rotationally symmetric surface (30 points)
Consider small particles moving with velocity parallel to the z-axis Particles are scattering from a perfectly elastic and frictionless surface The surface is rotationally symmetric about the z-axis and the shape of the surface is ρ(z) = z3 for z gt 0 We want to find differential scattering cross section σ(θ)
a) Find the relationship between the scattering angle θ and the impact parameter Note that the surface at the impact point can be considered as a perfectly elastic wall tangential to the curve at that point
b) Extract b(θ) and determine the differential cross section
c) Make a sketch of the scattering angle at some representative point ρ(z) for the case of the surface that is frictionless but totally inelastic
d) Make a sketch of the scattering angle at some representative point ρ(z) for the case of surface that is elastic but it has very high friction
6
Problem 3 Motion in rotating frame (35 points)
Consider a cannon located at geographical lattitude of exactly 45o North Cannon can fire identical projectiles in East North West and South directions All projectiles have identical initial speed of v0 = 200 ms and the cannon always points up at exactly 45o to the horizontal In your calculations of the projectile trajectory you can ignore the curvature of the Earth Assume that there is no air resistance
Assume that the radius of the Earth is R = 6 middot106 m and that the angular velocity of Earthrsquos rotation is Ω = 7 middot 10minus5 sminus1 Gravitational acceleration is g = 10 ms2 Do your calculations in the coordinate system where the z-axis is vertical pointing up with 0 at the center of the Earth the x-axis points North and the y-axis points West
a) Assume that the Earth is not rotating Obtain the algebraic formulas and the numericals value for the total range in meters maximum height above the ground in meters and the projectile flight time in seconds
b) Assume now that the Earth is rotating with its usual Ω Write down an expresshy
sion for acceleration ai = (ax ay az) in terms of components of r = (x y z) and Ω v = (x y˙ z) Ignore very small terms proportional to Ω2x Ω2y and replace radicz with R Keep all variables in algebraic form but replace sin 45o and cos 45o with 1 2
Note the following sections can be quite time consuming Start them only after you have finalized the other problems and sections in this quiz
c) The gun is being shot in the four geographical directions ENW S Write down the expressions for acceleration individually for each direction In each case remove the very small terms and find cancellations of terms of roughly equal size Justify your choices Note that some numerical cancellations are possible since the speed of the projectile happens to be very close to the linear speed of the Earthrsquos surface at that lattitude
d) Based on the magnitudes and signs of the terms of a obtained in c) estimate the effect of the earthrsquos rotation on the position of the impact parameter of the projectile for each of the four cases Mark the location of the new impact point as compared to no-rotation impact point (as obtained in a)) on graphs similar to Figure 1 The center of the graph corresponds to the no-rotation impact position Do not do the precise calculations try only to estimate the direction and relative magnitude of the deviation All four graphs should be oriented with North at the top and East to the right
7
x
yNorth
East
West
South
Figure 1 Impact Point Graph
6
Problem 3 Motion in rotating frame (35 points)
Consider a cannon located at geographical lattitude of exactly 45o North Cannon can fire identical projectiles in East North West and South directions All projectiles have identical initial speed of v0 = 200 ms and the cannon always points up at exactly 45o to the horizontal In your calculations of the projectile trajectory you can ignore the curvature of the Earth Assume that there is no air resistance
Assume that the radius of the Earth is R = 6 middot106 m and that the angular velocity of Earthrsquos rotation is Ω = 7 middot 10minus5 sminus1 Gravitational acceleration is g = 10 ms2 Do your calculations in the coordinate system where the z-axis is vertical pointing up with 0 at the center of the Earth the x-axis points North and the y-axis points West
a) Assume that the Earth is not rotating Obtain the algebraic formulas and the numericals value for the total range in meters maximum height above the ground in meters and the projectile flight time in seconds
b) Assume now that the Earth is rotating with its usual Ω Write down an expresshy
sion for acceleration ai = (ax ay az) in terms of components of r = (x y z) and Ω v = (x y˙ z) Ignore very small terms proportional to Ω2x Ω2y and replace radicz with R Keep all variables in algebraic form but replace sin 45o and cos 45o with 1 2
Note the following sections can be quite time consuming Start them only after you have finalized the other problems and sections in this quiz
c) The gun is being shot in the four geographical directions ENW S Write down the expressions for acceleration individually for each direction In each case remove the very small terms and find cancellations of terms of roughly equal size Justify your choices Note that some numerical cancellations are possible since the speed of the projectile happens to be very close to the linear speed of the Earthrsquos surface at that lattitude
d) Based on the magnitudes and signs of the terms of a obtained in c) estimate the effect of the earthrsquos rotation on the position of the impact parameter of the projectile for each of the four cases Mark the location of the new impact point as compared to no-rotation impact point (as obtained in a)) on graphs similar to Figure 1 The center of the graph corresponds to the no-rotation impact position Do not do the precise calculations try only to estimate the direction and relative magnitude of the deviation All four graphs should be oriented with North at the top and East to the right
7
x
yNorth
East
West
South
Figure 1 Impact Point Graph
7
x
yNorth
East
West
South
Figure 1 Impact Point Graph