### Civil Engineering - Applied Mechanics MCQs Part 5

1. The centre of gravity of a homogenous body is the point at which the whole

A.
volume of the body is assumed to be concentrated
B.
area of the surface of the body is assumed to be concentrated
C.
weight of the body is assumed to be concentrated
D.
all the above.

2. Pick up the correct statement from the following :

A.
If two equal and perfectly elastic smooth spheres impinge directly, they interchange their velocities.
B.
If a sphere impinges directly on an equal sphere which is at rest, then a fraction (1 - e2) the original kinetic energy is lost by the impact.
C.
If a smooth sphere impinges on another sphere, which is at rest, the latter will move along the line of centres.
D.
If two equal spheres which are perfectly elastic impinge at right angles, their direction after impact will still be at right angles.
E.
All the above.

3. Centre of gravity of a thin hollow cone lies on the axis of symmmetry at a height of

A.
one-half of the total height above base
B.
one-third of the total height above base
C.
one-fourth of the total height above base
D.
none of these.

4. A ball of mass 1 kg moving with a velocity of 2 m/sec collides a stationary ball of mass 2 kg and comes to rest after impact. The velocity of the second ball after impact will be

A.
zero
B.
0.5 m/sec
C.
1.0 m/sec
D.
2.0 m/sec.

5. Periodic time of a particle moving with simple harmonic motion is the time taken by the particle for

A.
half oscillation
B.
quarter oscillation
C.
complete oscillation
D.
none of these.

6. The reaction at the central support B of the beam ABC hinged at D shown in below figure is

A. 2 t
B. 5.8 t
C. 0.2 t
D. 3.5 t.

7. The motion of a bicycle wheel is

A. translatory
B. rotary
C. rotary and translatory
D. curvilinear

8. The displacement of a particle which moves along a straight line is given by S = 4t3 + 3t2 - 10 where S is in meters and t is in seconds. The time taken by the particle to acquire a velocity of 18 m/sec from rest, is

A. sec
B. 1 sec
C. 1.5 sec
D. 1.5 sec.

9. If the resultant of two forces P and Q acting at an angle θ makes an angle α with P, then tan α equals

A.
B.
C.
D.

10. Pick up the correct statement from the following. The kinetic energy of a body

A. before impact is equal to that after impact
B. before impact is less than that after impact
C. before impact is more than that after impact
D. remains constant
E. none of these.

11. A particle moving with a simple harmonic motion, attains its maximum velocity when it passes

A. the extreme point of the oscillation
B. through the mean position
C. through a point at half amplitude
D. none of these.

12. The moment of intertia of a circular lamina of diameter d, about an axis perpendicular to the plane of the lamina and passing through its centre, is

A.
B.
C.
D.
E.

13. The unit of impulse, is

A. kg.m/sec
B. kg.m/sec3
C. kg.m/sec2
D. kg.m2/sec.

14. If l is the span of a light suspension bridge whose each cable carries total weight (w) and the central dip is y, the horizontal pull at each support, is

A.
B.
C.
D. wl.

15. The practical units of work, is

A. erg
B. joule
C. Newton
D. dyne.

16. The rate of change of displacement of a body with respect to its surrounding, is known

A. velocity
B. acceleration
C. speed
D. none of these.

17. The C.G. of a hemisphere from its base measured along the vertical radius is at a distance of

A.
B.
C.
D.
E. R/2.

18. The Centre of gravity of a 10 x 15 x 5 cm T section from its bottom, is

A. 7.5 cm
B. 5.0 cm
C. 8.75 cm
D. 7.85 cm
E. none of above.

19. For a self-locking machine, the efficiency should be

A. less than 60%
B. 50%
C. more than 50%
D. None of these.

20. When a body moves round a fixed axis, it has

A. a rotary motion
B. a circular motion
C. a translatory
D. a rotary motion and translatory motion.

21. Power developed by a torque, is

A. 2πNT kg m/min
B.
C.
D. all the above.

22. From a solid cylinder of height 8 cm and radius 4 cm, a right circular cone is scooped out on the same base and having the same height as that of the cylinder. The c.g. of the remainder is at a height of

A. 4.5 cm
B. 5.0 cm
C. 5.25 cm
D. 5.5 cm.

23. The unit of moments in M.K.S system, is

A. kgm
B. kg/m2
C. kg/sec2
D. kg/sec.

24. The rotational velocity of a satellite is increased by 450 m per second if its launch is done from equator

A. eastward
B. northward
C. westward
D. southward
E. upward.

25. On a mass m describing a circular path of radius r, the centrifugal force

A. acts tangentially to the circular path
B. acts towards the centre of rotation
C. acts away from the centre of rotation
D. is

26. In the structure shown in below figure, the member which carries zero force, is

A. AB
B. BC
C. BE
D. BD
E. All the above.

27. When a body falls freely under gravitational force, it possesses

A. maximum weight
B. minimum weight
C. no weight
D. no effect on its weight.

28. A rigid body suspended Vertically at a point and oscillating with a small amplitude under the action of the force of gravity, is called

A. simple pendulum
B. compour pendulum
C. Second's pendulum
D. none of these.

29. If a ball which is dropped from a height of 2.25 m on a smooth floor attains the height of bounce equal to 1.00 m, the coefficient of the restitution between the ball and floor, is

A. 0.25
B. 0.50
C. 0.67
D. 0.33
E. 0.75

30. The piston of a steam engine moves with a simple harmonic motion. The crank rotates 120 r.p.m. and the stroke length is 2 metres. The linear velocity of the piston when it is at a distance of 0.5 metre from the centre, is

A. 5.88 m/sec
B. 8.88 m/sec
C. 10.88 m/sec
D. 12.88 m/sec.

31. The frequency of oscillation on moon as compared to that on earth, will be

A. 2.44 times more
B. 2.44 times less
C. 3 times less
D. 3 times more.

32. Moment of interia of a squares of side fa about an axis through its centre of gravity, is

A. b3/4
B. b4/12
C. b4/3
D. b4/8
E. b4/36.

33. The reaction at the support D of the continuous beam ABCD, hinged at two points shown in below figure is

A. 1.6 t ↑
B. 1.6 t ↓
C. 0.5 t ↑
D. 0.5 t ↓
E. 8.5 t ↑

34. When a body slides down an inclined surface, the acceleration (f) of the body, is given by

A. f = g
B. f = g sin θ
C. f = g cos θ
D. f = g tan θ.

35. The velocity ratio of an inclined plane of inclination θ with horizontal for lifting a load is

A. sin θ
B. cos θ
C. tan θ
D. sec θ
E. cosec θ.

36. Pick up the incorrect statement from the following. In a simple harmonic motion

A. velocity is maximum at its mean position
B. velocity is minimum at the end of the storke
C. acceleration is minimum at the end of the stroke
D. acceleration is zero at the mean position.

37. The gravitational force makes a satellite go round the earth in a circular orbit, if it is projected with an initial velocity of

A. 8.04 km/sec at a height of 285 km
B. 11.11 km/sec at a height of 37, 400 km
C. 11.26 km/sec, the satellite escapes the pull of the earth
D. all the above.

38. The point about which combined motion of rotation and translation of a rigid body takes place, is known as

A. Virtual centre
B. Instantaneous centre
C. Instantaneous axis
D. Point of rotation
E. All the above.

39. A particle is dropped from the top of a tower 60 m high and another is projected upwards from the foot of the tower to meet the first particle at a height of 15.9 m. The velocity of projection of the second particle is

A. 16 m/sec
B. 18 m/sec
C. 20 m/sec
D. 22 m/sec.

40. A point subjected to a number of forces will be in equilibrium, if

A. sum of resolved parts in any two directions at right angles, are both zero
B. algebraic sum of the forces is zero
C. two resolved parts in any two directions at right angles are equal
D. algebraic sum of the moments of the forces about the point is zero
E. none of these.

41. The moment of inertia of a triangular section (base b, height h) about centroidal axis parallel to the base, is

A.
B.
C.
D.
E.

42. The horizontal reaction at the support A of the structure shown in below figure, is

A. zero
B. 1 t
C. 2 t
D. 3 t
E. 2.5 t.

43. Periodic time of body moving with simple harmonic motion, is

A. directly proportional to its angular velocity
B. directly porportional to the square of its angular velocity
C. inversly proportional to the square of its angular velocity
D. inversely proportional to its angular velocity.

44. On a ladder resting on a rough ground and leaning against a smooth vertical wall, the force of friction acts

A. downwards at its upper end
B. upwards at its upper end
C. perpendicular to the wall at its upper end
D. zero at its upper end
E. none of these.

45. The centre of gravity of a plane lamina will not be at its geometrical centre if it is a

A. circle
B. equilateral triangle
C. rectangle
D. square
E. right angled triangle.

46. The motion of a particle moving with S.H.M. from an extremity to the other, constitutes

A. half an oscillation
B. one full oscillation
C. two oscillations
D. none of these.

47. Two parallel forces 20 kg and 15 kg act. In order that the distance of the resultant from 20 kg force may be the same as that of the former resultant was from 15 kg, the 20 kg force is diminished by

A. 5.5 kg
B. 6.25 kg
C. 8.75 kg
D. 10.5 kg.

48. The velocity of a moving body, is

A. a vector quantity
B. a scalar quantity
C. a constant quantity
D. none of these.

49. If two equal forces of magnitude P act at an angle θ, their resultant, will be

A. P cos θ/2
B. 2P sin θ/2
C. P tan θ/2
D. 2P cos θ/2
E. P sin θ/2.

50. A body of weight 14 g appears to weight 13 g when weighed by a spring balance in a moving lift. The acceleration of the lift at that moment was

A. 0.5 m/sec2
B. 0.7 m/sec2
C. 1 m/sec2
D. 1 cm/sec2.