Code No: CE1501 R14Model Question Paper

I B. Tech I Semester External ExaminationsENGINEERING MECHANICS

(Common to Civil Engineering, Mechanical Engineering)Time: 3 Hours Max. Marks: 60

Note: All Questions from Part A are to be answered at one place.

Answer any Four Questions from Part B

PART - A 6 X 2 = 12 M

1. All ball of weight ‘W’ is supported on a smooth vertical wall by tieing a rod as shown in Fig.1(a).

Draw the free body diagram showing the forces acting on the ball.

2. A body of weight 200N is placed on a rough horizontal plane as in Fig1(b). If the coefficient of friction

between the body and the plane is 0.3, determine the horizontal force required to impend motion.

3. For a triangle of base width 4cm and altitude height 6cm, find the moment of inertia about its base.

4. State Pappu’s theorem to determine the volume of solids.

5. A lift has an upward acceleration of 9.81m/s2. What pressure will a man weighing 500N exert on the

floor of the lift?

6. A body, with initial velocity zero, falls vertically from a height ‘h’ and strikes the ground. Using work

– energy principle, find the striking velocity.

PART- B 4 X 12 = 48 M

1. a) A regular hexagon is subjected to an action of five forces originating from one node point

towards other five node points as shown in Fig.1(a). Show that the resultant passes through

50N force. 6M

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b) A rigid bar AB is supported in a vertical plane and carries a load Q at its free end as shown in

Fig.1(b). Neglecting the weight of the bar itself, compute the magnitude of the tensile forces S

induced in the horizontal string CD. 6M

2.

a) What is the value of P in the system shown in Fig.2(a) to cause motion to impend? Assume

pulley is smooth and coefficient of friction between the other contact surfaces is 0.20.

6M

b) Derive the expression for the ratio of tensions on tight side and slack side of a flat belt passing

over pulley, when it is just on the point of slipping. 6M

3.

a) Determine the moment of inertia of the following I – section shown in Fig.3(a) about both

‘xx’ and ‘yy’ axes passing through its centroid. 6M

b) Using Pappu’s & Guldinus theorem, determine the volume of a sphere. 6M

4.

a) Derive the expression for Mass moment of inertia of right circular cone about its axis of

rotation whose base radius is ‘R’ and altitude height ‘h’. 6M

b) In frame shown in Fig.4(b), diagonal member AC is attached in horizontal direction. If a

360N weight is suspended at the bottom of the frame, how much compressive force will be

induced in the diagonal AC? Assume bars are weightless, θ = 350 and L=1.7m. Use virtual

work principle. 6M

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5.

a) A bullet moving at the rate of 250m/sec is fired into a log of wood. The bullet penetrates to a

depth of 0.4m. If the bullet moving with the same velocity is fired into a similar piece of wood

of 0.2m thick, with what velocity would the bullet emerge outside? Take the resistance is

uniform in both the cases. 6M

b) Two weights 800N and 200N are connected by thread and move along a rough horizontal

plane under the action of a force 400N applied to 800N weight as shown in Fig.5(b). If the

coefficient of friction between sliding weights and the plane is 0.3, determine the acceleration

of the system and tension in the string. 6M

6.

a) Two blocks in Fig.6(a) having weights P=10kg and Q=5kg and coefficient of friction between

block P and the horizontal plane is μ =0.25. If the system is released from rest and the block Q

falls a vertical distance h = 0.6m, what velocity ‘v’ will acquire? Use work – Energy principle.

Neglect friction in pulley. 6M

(b) A glass marble, whose weight is 0.2N, falls from a height of 8m and rebounds to a height of 6

meters. Find the impulse and the average force between the marble and the floor, if the time

during which they are in contact is 1/10 of a second 6M

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