Civil Engineering - Applied Mechanics MCQs Part 1

1. The centre of gravity of a triangle is at the point where three

A.
medians of the triangle meet
B.
perpendicular bisectors of the sides of the triangle meet
C.
bisectors of the angle of the triangle meet
D.
none of these.

2. The forces which meet at one point and have their lines of action in different planes are called

A.
coplaner non-concurrent forces
B.
non-coplaner concurrent forces
C.
non-coplaner non-current forces
D.
intersecting forces
E.
none of these.

3. At a given instant ship A is travelling at 6 km/h due east and ship B is travelling at 8 km/h due north. The velocity of B relative to A is

A.
7 km/hrs
B.
2 km/hrs
C.
1 km/hrs
D.
10 km/hrs
E.
14 km/hrs.

4. The equation of motion of a particle starting from rest along a straight line is x = t3 - 3t2 + 5. The ratio of the accelerations after 5 sec and 3 sec will be

A.
2
B.
3
C.
4
D.
5

5. The locus of the instantaneous centre of a moving rigid body, is

A.
straight line
B.
involute
C.
centroid
D.
spiral.

6. A projectile is thrown at an angle a to the horizontal with α velocity v. It will have the maximum centripetal acceleration

A. at the start
B. at the top of the trajectory
C. as it strikes the ground
D. else where.

7. The c.g. of the shaded area of the below figure whose curve OM is a parabola from y-axis, is

A.
B.
C.
D.
E.

8. The unit of Moment of Inertia of a body, is

A. m
B. m2
C. m3
D. m4
E. none of these.

9. If a body moves in such a way that its velocity increases by equal amount in equal intervals of time, it is said to be moving with

A. a uniform retardation
B. a uniform acceleration
C. a variable acceleration
D. a variable retardation
E. none of these.

10. If the gravitational accelerational at any place is doubled, the weight of a body, will

A. be reduced to half
B. be doubled
C. not be affected
D. none of these.

11. A cable loaded with 0.5 tonne per horizontal metre span is stretched between supports in the same horizontal line 400 m apart. If central dip is 20 m, the minimum tension in the cable, will be

A. 200 tonnes at the centre
B. 500 tonnes at the centre
C. 200 tonnes at the right support
D. 200 tonnes at the left support.

12. A particle moves along a straight line such that distance x traversed in t seconds is given by x = t2(t + 1), the acceleration of the particle, will be

A. 3t3 - 2t
B. 3t2 + 2t
C. 6t - 2
D. 6t + 2
E. 3t - 2

13. The Law of Polygon of Forces states that

A. if a polygen representing the forces acting at point in a body is closed, the forces are in equilibrium
B. if forces acting on a point can be represented in magnitde and direction by the sides of a polygon taken in order, then the resultant of the forces will be represented in magnitude and direction by the closing side of the polygon
C. if forces acting on a point can be represented of a polygon taken in order, their sides of a polygon taken in order, their resultant will be represented in magnitude and direction by the closing side of the polygon, taken in opposite order
D. if forces acting on a point can be represented in magnitude and direction by the sides of a polygon in order, the forces are in equilibrium.

14. Parallelogram Law of Forces states, "if two forces acting simultaneously on a particle be represented in magnitude and direction by two adjacent sides of a parallelogram, their resultant may be represented in magnitude and direction by

A. its longer side"
B. its shorter side"
C. the diagonal of the parallelogram which does not pass through the point of intersection of the forces"
D. the diagonal of the parallelogram which passes through the point of intersection of the forces"
E. half the sum of the diagonals".

15. Which one of the following statements is true ?

A. The tangent of the angle of friction is equal to coefficeint of friction
B. The angle of repose is equal to angle of friction
C. The tangent of the angle of repose is equal to coefficient of friction
D. All the above.

16. The beam shown in below figure is supported by a hinge at A and a roller at B. The reaction RA of the hinged support A of the beam, is

A. 10.8 t
B. 10.6 t
C. 10.4 t
D. 10.2 t.

17. The product of mass and velocity of a moving a body, is called

A. moment
B. momentum
C. power
D. impulse.

18. Engineer's units of force, is

A. Newton in absolute units
B. Dyne in absolute units
C. Newton and dyne in absolute units
D. All the above.

19. Joule is the unit of

A. work
B. force
C. power
D. torque
E. none of these.

20. The maximum velocity of a body vibrating with a simple harmonic motion of amplitude 150 mm and frequency 2 vibrations/sec, is

A. 188.5 m/sec
B. 18.85 m/sec
C. 1.885 m/sec
D. 0.18845 m/sec.

21. If the tension in a cable supporting a lift moving upwards is twice the tension when the lift is movng downwards, the acceleration of the lift, is

A.
B.
C.
D.

22. One Newton force, is

A. 103 dynes
B. 104 dynes
C. 105 dynes
D. 106 dynes
E. 107 dynes.

23. The masses of two balls are in the ratio of 2 : 1 and their respective velocities are in the ratio of 1 : 2 but in opposite direction before impact. If the coefficient of restitution is , the velocities of separation of the balls will be equal to

A. original velocity in the same direction
B. half the original velocity in the same direction
C. half the original velocity in the opposite direction
D. original velocity in the opposite direction

24. The angle which an inclined surface makes with the horiontal when a body placed on it is on the point of moving down, is called

A. angle of repose
B. angle of friction
C. angle of inclination
D. none of these.

25. Work may be defined as

A. force x distance
B. force x velocity
C. force x acceleration
D. none of these.

26. A square hole is punched out of a circular lamina, the diagonal of the square being the radius of the circle. If r is the radius of the circle, the C.G. of the remainder from the corner of the square on the circumference will be

A.
B.
C.
D.

27. A bullet weighing 200 g is fired horizontally with a velocity of 25 m/sec from a gun carried on a carriage which together with the gun weighs 100 kg. The velocity of recoil of the gun, will be

A. 0.01 m/sec
B. 0.05 m/sec
C. 1.00 m/sec
D. 1.5 m/see.

28. The tension in a cable supporting a lift

A. is more when the lift is moving downwards
B. is less when the lift is moving upwards
C. remains constant whether its moves downwards or upwards
D. is less when the lift is moving downwards.

29. A satellite moves in its orbit around the earth due to

A. Gravitational force
B. Centripetal force
C. Centrifugal force
D. none of these.

30. If g1 and g2 are the gravitational accelerations on two mountains A and B respectively, the weight of a body when transported from A to B will be multiplied by

A. g1
B. g2
C.
D.

31. If three rigid rods are hinged together to form a triangle and are given rotary as well as translatory motion, the number of instantaneous centres of the triangle, will be

A. 1
B. 2
C. 3
D. 4
E. 5.

32. The mechanical advantage of an ideal machine is 100. For moving the local through 2 m, the effort moves through

A. 0.02 m
B. 2 m
C. 2.5 m
D. 20 m.

33. When a body in equilibrium undergoes an infinitely small displacement, work imagined to be done, is known as

A. imaginary work
B. negative work
C. virtual work
D. none of these.

34. The resultant of two forces P and Q acting at an angle θ, is

A. P2 + Q2 + 2P sin θ
B. P2 + Q2 + 2PQ cos θ
C. P2 + Q2 + 2PQ tan θ
D.
E.

35. To attain the synchronous orbit, the launch of a satellite, is done from a place

A. on equator
B. on 30° latitude
C. on 45° latitude
D. on 60° latitude
E. on the poles.

36. The vertical reaction at the support A of the structure shown in below figure, is

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

37. Pick up the correct statement from the following :

A. Nature plays an important role in the launch of a satellite
B. The earth's gravity reduces the speed of a satellite by 32 km per second
C. The gravitational force relents as the satellite climbs higher
D. The gravitational intensity declines with height
E. All the above.

38. If the radius of the earth is 600 km the height of a mountain above sea level at the top of which a beat seconds pendulum at sea level, looses 27 seconds a day, is

A. 500 metres
B. 1000 metres
C. 1500 metres
D. 2000 metres
E. 25000 metres.

39. The total time of collision and restitution of two bodies, is called

A. time of collision
B. period of collision
C. period of impact
D. all the above.

40. The length of a Second's pendulum, is

A. 99.0 cm
B. 99.4 cm
C. 100 cm
D. 101 cm
E. 101.10 cm.

41. A load of 500 kg was lifted through a distance of 13 cm. by an effort of 25 kg which moved through a distance of 650 cm. The efficiency of the lifting machine is

A. 50%
B. 40%
C. 55%
D. 30%.

42. Maximum efficiency of a screw jack for the angle of friction φ, is

A.
B.
C.
D.

43. A string of length 90 cm is fastened to two points A and B at the same level 60 cm apart. A ring weighing 120 g is slided on the string. A horizontal force P is applied to the ring such that it is in equilibrium vertically below B. The value of P is :

A. 40 g
B. 60 g
C. 80 g
D. 100 g.

44. The reaction at the support A of the beam shown in below figure is

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

45. u1 and u2 are the velocities of approach of two moving bodies in the same direction and their corresponding velocities of separation are v1 and v2. As per Newton's law of collision of elastic bodies, the coefficient of restitution (e) is given by

A.
B.
C.
D.

46. The c.g. of a thin hollow cone of height h, above its base lies on the axis, at a height of

A.
B.
C.
D.

47. Two forces act an angle of 120°. If the greater force is 50 kg and their resultant is perpendicular to the smaller force, the smaller force is

A. 20 kg
B. 25 kg
C. 30 kg
D. 35 kg
E. 40 kg.

48. The C.G. of a right circular cone lies on its axis of symmetry at a height of

A. h/2
B. h/3
C. h/4
D. h/5
E. h/6.

49. A uniform rod 9 m long weighing 40 kg is pivoted at a point 2 m from one end where a weight of 120 kg is suspended. The required force acting at the end in a direction perpendicular to rod to keep it equilibrium, at an inclination 60° with horizontal, is

A. 40 kg
B. 60 kg
C. 10 kg
D. 100 kg.

50. If a particle is projected inside a horizontal tunnel which is 554 cm high with a velocity of 60 m per sec, the angle of projection for maximum range, is

A. 8°
B. 9°
C. 10°
D. 11°
E. 12°.