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8/17/2019 EM102 Topic 1
1/28
Statics, Fourteenth EditionR.C. Hibbeler
Copyright ©2016 by Pearson Education, Inc.All rights reserved.
EM102 Engineering Statics
1. Introduction
2. Force vectors
3. Rigid bodies
4. Equilibrium of rigid bodies
5. Structural analysis
6. Friction
7. Distribution of forces
Dr. Elango Natarajan
Assistant Professor
Aug 2015
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Statics, Fourteenth EditionR.C. Hibbeler
Copyright ©2016 by Pearson Education, Inc.All rights reserved.
References
• ENGINEERING MECHANICS/STATICS (12th Edition), by R.C. Hibbler.
Prentice Hall. 2010.
• VECTOR MECHANICS FOR ENGINEER: STATICS, by F.P. Beer, E.R.
Johnston. McGraw Hill. 2012.
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Statics, Fourteenth EditionR.C. Hibbeler
Copyright ©2016 by Pearson Education, Inc.All rights reserved.
EM102 Engineering Statics
Topic 1: Introduction
Fundamental concepts,
unit of measurements,procedure for analysis,
numerical accuracy.
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Statics, Fourteenth EditionR.C. Hibbeler
Copyright ©2016 by Pearson Education, Inc.All rights reserved.
In-Class activities:
• Reading Quiz
• What is Mechanics?• System of Units
• Numerical Calculations
• Concept Quiz
• Problem-Solving Strategy
• Attention Quiz
Today’s Objectives:Students will be able to:
a) Explain mechanics/statics.
b) Work with two types of units.
c) Round the final answer appropriately.
d) Apply problem-solving strategies.
MECHANICS, UNITS, NUMERICAL CALCULATIONS &GENERAL PROCEDURE FOR ANALYSIS
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Statics, Fourteenth EditionR.C. Hibbeler
Copyright ©2016 by Pearson Education, Inc.All rights reserved.
Study of what happens to a “thing” (the technical name is“BODY”) when FORCES are applied to it.
Either the body or forces can be large or small.
WHAT IS MECHANICS?
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Statics, Fourteenth EditionR.C. Hibbeler
Copyright ©2016 by Pearson Education, Inc.All rights reserved.
Recap
•Load or Force - a push or pull exerted by a body.
•Types of loads – static load and dynamic load
•Stress - pressure or tension exerted on a
material or object.
•Strain – the relative change occurred due to the
application of force on a body or object.
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Statics, Fourteenth EditionR.C. Hibbeler
Copyright ©2016 by Pearson Education, Inc.All rights reserved.
Recap
•Modulus of elasticity
•Stiffness
8/17/2019 EM102 Topic 1
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Statics, Fourteenth EditionR.C. Hibbeler
Copyright ©2016 by Pearson Education, Inc.All rights reserved.
Statics Dynamics
Rigid Bodies
(Things that do not change shape)
Deformable Bodies
(Things that do change shape)
Incompressible Compressible
Fluids
Mechanics
BRANCHES OF MECHANICS
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Statics, Fourteenth EditionR.C. Hibbeler
Copyright ©2016 by Pearson Education, Inc.All rights reserved.
Rigid body
•Rigid body can be considered as a combination of
large number of particles in which all the particles
remain at a fixed distance from one another both
before and after applying a load.
•The deformation of such bodies is very small.
•Machines, mechanisms are considered to be rigid
bodies.
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Statics, Fourteenth EditionR.C. Hibbeler
Copyright ©2016 by Pearson Education, Inc.All rights reserved.
Statics & Dynamics
•Statics deals with the equilibrium of bodies that are
either rest or move with a constant velocity.
•Dynamics is concerned with the accelerated motion
of bodies.
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Statics, Fourteenth EditionR.C. Hibbeler
Copyright ©2016 by Pearson Education, Inc.All rights reserved.
1. The subject of mechanics deals with what happens to a bodywhen ______ is/are applied to it.
A) a magnetic field B) heat C) forces
D) neutrons E) lasers
2. ________________ still remains the basis of most of today’s
engineering sciences.
A) Newtonian Mechanics B) Relativistic Mechanics
C) Greek Mechanics C) Euclidean Mechanics
READING QUIZ
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Statics, Fourteenth EditionR.C. Hibbeler
Copyright ©2016 by Pearson Education, Inc.All rights reserved.
Four fundamental physical quantities (or dimensions).
• Length
• Mass
• Time
• Force
Newton’s 2nd Law relates them: F = m × a
We use this equation to develop systems of units.
Units are arbitrary names we give to the physical quantities.
UNITS OF MEASUREMENT(Section 1.3)
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Statics, Fourteenth EditionR.C. Hibbeler
Copyright ©2016 by Pearson Education, Inc.All rights reserved.
Force, mass, time and acceleration are related by Newton’s 2nd law. Three of these are assigned units (called base units)
and the fourth unit is derived. Which one is derived varies by
the system of units.
UNIT SYSTEMS
We will work with two unit systems in statics:
• International System (SI)
• U.S. Customary (USCS)
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Statics, Fourteenth EditionR.C. Hibbeler
Copyright ©2016 by Pearson Education, Inc.All rights reserved.
Table 1-1 in the textbook summarizes these unit systems.
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Statics, Fourteenth EditionR.C. Hibbeler
Copyright ©2016 by Pearson Education, Inc.All rights reserved.
COMMON CONVERSION FACTORS
Work problems in the units given unless otherwise instructed!
Answer is 209.06 N
Can you convert a force value of 47 lb into SI units?
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Statics, Fourteenth EditionR.C. Hibbeler
Copyright ©2016 by Pearson Education, Inc.All rights reserved.
• No plurals (e.g., m = 5 kg, not kgs )
• Separate units with a • (e.g., meter second = m • s )
• Most symbols are in lowercase.
• Key exceptions are N, Pa, M and G.
• Exponential powers apply to units, e.g., cm • cm = cm2
• Compound prefixes should not be used.
• Table 1-3 in the textbook shows prefixes used in the SI
system
THE INTERNATIONAL SYSTEM OF UNITS(Section 1.4)
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Statics, Fourteenth EditionR.C. Hibbeler
Copyright ©2016 by Pearson Education, Inc.All rights reserved.
Table 1 – 3 shows some of the prefixes usedin the SI system.
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Statics, Fourteenth EditionR.C. Hibbeler
Copyright ©2016 by Pearson Education, Inc.All rights reserved.
DIMENSION
Dimension is a measure of physical quantity without numerical values.
Example: Length, Area, Diameter, Weight
Unit is a way to assign a number to the dimension.
Example: mm, kg.
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Statics, Fourteenth EditionR.C. Hibbeler
Copyright ©2016 by Pearson Education, Inc.All rights reserved.
NUMERICAL CALCULATIONS(Section 1.5)
Be consistent when rounding off.
- greater than 5, round up (3528 3530)- smaller than 5, round down (0.03521 0.0352)
- equal to 5, see your textbook for an explanation.
Use an appropriate number of significant figures (3 foranswer, at least 4 for intermediate calculations). Why?
Must have dimensional “homogeneity.” Dimensions have to be the same on both sides of the equal sign, (e.g. distance =
speed time.)
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Statics, Fourteenth EditionR.C. Hibbeler
Copyright ©2016 by Pearson Education, Inc.All rights reserved.
1. Evaluate the situation in which mass (kg), force (N), and
length (m) are the base units and recommend one of the
following.
A) A new system of units will have to be formulated.
B) Only the unit of time have to be changed from second to
something else.
C) No changes are required.D) The above situation is not feasible.
CONCEPT QUIZ
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Copyright ©2016 by Pearson Education, Inc.All rights reserved.
2. Give the most appropriate reason for using three significantfigures in reporting results of typical engineering calculations.
A) Historically slide rules could not handle more than three
significant figures.
B) Three significant figures gives better than one-percent
accuracy.
C) Telephone systems designed by engineers have area codes
consisting of three figures.
D) Most of the original data used in engineering calculations do
not have accuracy better than one percent.
CONCEPT QUIZ (continued)
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Copyright ©2016 by Pearson Education, Inc.All rights reserved.
2. In the three-step approach to problem solving called IPE,
what does P stand for?
A) Position B) Plan C) Problem
D) Practical E) Possible
1. For a static’s problem, your calculations show the final answer as12345.6 N. What should you write as your final answer?
A) 12345.6 N B) 12.3456 kN C) 12 kN
D) 12.3 kN E) 123 kN
ATTENTION QUIZ
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Statics, Fourteenth EditionR.C. Hibbeler
Copyright ©2016 by Pearson Education, Inc.All rights reserved.
example_01_01
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example_01_02
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example_01_03
continued on next slide
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Copyright ©2016 by Pearson Education, Inc.All rights reserved.
example_01_03 (continued)
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