1000+ Engineering Mechanics Multiple Choice Question Answer [Solved]

1. The moment of inertia of a square of side (a) about an axis through its centre of gravity is
A. a⁴/4
B. a⁴/8
C. a⁴/12
D. a⁴/36
Answer : C

2. The unit of work in S.I. units is
A. Newton
B. erg
C. kg-m
D. joule
Answer : D

3. Two balls of equal mass and of perfectly elastic material are lying on the floor. One of the balls with velocity v is made to strike the second ball. Both the balls after impact will move with a velocity
A. v
B. v/2
C. v/4
D. v/8
Answer : B

4. The range of a projectile is maximum, when the angle of projection is
A. 30°
B. 45°
C. 60°
D. 90°
Answer : B

5. If the gravitational acceleration at any place is doubled, then the weight of a body will be
A. g/2
B. g
C. ?2.g
D. 2g
Answer : D

6. Two like parallel forces are acting at a distance of 24 mm apart and their resultant is 20 N. It the line of action of the resultant is 6 mm from any given force, the two forces are
A. 15 N and 5 N
B. 20 N and 5 N
C. 15 N and 15 N
D. None of these
Answer : A

7. One end of a helical spring is fixed while the other end carries the load W which moves with simple harmonic motion. The frequency of motion is given by (where ? = Deflection of the spring.)
A. 2?. ?(g/?)
B. 1/2?. ?(g/?)
C. 2?. ?(?/g)
D. 1/2?. ?(?/g)
Answer : B

8. If tension in the cable supporting a lift moving downwards is half the tension when it is moving upwards, the acceleration of the lift is
A. g/2
B. g/3
C. g/4
D. None of these
Answer : D

9. The unit of force in S.I. system of units is
A. Dyne
B. Kilogram
C. Newton
D. Watt
Answer : C

10. In a screw jack, the effort required to lower the load is __________ the effort required to raise the same load.
A. Less than
B. Equal to
C. More than
D. None of these
Answer : A

11. D' Alembert's principle is used for
A. Reducing the problem of kinetics to equivalent statics problem
B. Determining stresses in the truss
C. Stability of floating bodies
D. Designing safe structures
Answer : A

12. According to Lamis theorem
A. The three forces must be equal
B. The three forces must be at 120° to each other
C. The three forces must be in equilibrium
D. If the three forces acting at a point are in equilibrium, then each force is proportional to the sine of the angle between the other two
Answer : D

13. Which of the following are vector quantities?
A. Angular displacement
B. Angular velocity
C. Angular acceleration
D. All of these
Answer : D

14. Which of the following is a vector quantity?
A. Energy
B. Mass
C. Momentum
D. Angle
Answer : C

15. The unit of angular velocity is
A. m/min
B. rad/s
C. Revolutions/min
D. Both (B) and (C)
Answer : D

16. The mechanical advantage of a lifting machine is the ratio of
A. Distance moved by effort to the distance moved by load
B. Load lifted to the effort applied
C. Output to the input
D. All of the above
Answer : B

17. When a body falls freely under gravitational force, it possesses __________ weight.
A. No
B. Minimum
C. Maximum
D. None of these
Answer : A

18. Which of the following is not a vector quantity?
A. Weight
B. Velocity
C. Acceleration
D. Force
Answer : A

19. The moment of inertia of a thin rod of mass m and length l, about an axis through its centre of gravity and perpendicular to its length is
A. ml²/4
B. ml²/ 6
C. ml²/8
D. ml²/12
Answer : D

20. For a self locking machine, the efficiency must be
A. Equal to 50 %
B. Less than 50 %
C. Greater than 50 %
D. 100 %
Answer : B

21. On a ladder resting on smooth ground and leaning against vertical wall, the force of friction will be
A. Towards the wall at its upper end
B. Away from the wall at its upper end
C. Upwards at its upper end
D. Downwards at its upper end
Answer : C

22. The process of finding out the resultant force is called __________ of forces.
A. Composition
B. Resolution
C. Decomposition
D. None of these
Answer : A

23. In the lever of third order, load W, effort P and fulcrum F are oriented as ollows
A. W between P and F
B. F between W and P
C. P between W and F
D. W, P and F all on one side
Answer : A

24. In determining stresses in frames by methods of sections, the frame is divided into two parts by an imaginary section drawn in such a way as not to cut more than
A. Two members with unknown forces of the frame
B. Three members with unknown forces of the frame
C. Four members with unknown forces of the frame
D. Three members with known forces of the frame
Answer : B

25. The static friction
A. Bears a constant ratio to the normal reaction between the two surfaces
B. Is independent of the area of contact, between the two surfaces
C. Always acts in a direction, opposite to that in which the body tends to move
D. All of the above
Answer : D

26. A rubber ball is dropped from a height of 2 m. If there is no loss of velocity after rebounding, the ball will rise to a height of
A. 1 m
B. 2 m
C. 3 m
D. 4 m
Answer : B

27. The three forces of 100 N, 200 N and 300 N have their lines of action parallel to each other but act in the opposite directions. These forces are known as
A. Coplanar concurrent forces
B. Coplanar non-concurrent forces
C. Like parallel forces
D. Unlike parallel forces
Answer : D

28. Angle of friction is the
A. Angle between normal reaction and the resultant of normal reaction and the limiting friction
B. Ratio of limiting friction and normal reaction
C. The ratio of minimum friction force to the friction force acting when the body is just about to move
D. The ratio of minimum friction force to friction force acting when the body is in motion
Answer : A

29. A lead ball with a certain velocity is made to strike a wall, it falls down, but rubber ball of same mass and with same velocity strikes the same wall, it rebounds. Select the correct reason from the following:
A. Both the balls undergo an equal change in momentum
B. The change in momentum suffered by rubber ball is more than the lead ball
C. The change in momentum suffered by rubber ball is less than the lead ball
D. None of the above
Answer : B

30. The bellow figure shows the two equal forces at right angles acting at a point. The value of force R acting along their bisector and in opposite direction is
A. P/2
B. 2P
C. ?2 × P
D. P/?2
Answer : C

31. A body will begin to move down an inclined plane if the angle of inclination of the plane is _________ the angle of friction.
A. Equal to
B. Less than
C. Greater than
D. None of these
Answer : C

32. Concurrent forces are those forces whose lines of action
A. Lie on the same line
B. Meet at one point
C. Meet on the same plane
D. None of these
Answer : B

33. Moment of inertia of a hollow rectangular section as shown in the below figure about X-X axis, is
A. (BD³/12) - (bd³/12)
B. (DB³/12) - (db³/12)
C. (BD³/36) - (bd³/36)
D. (DB³/36) - (db³/36)
Answer : A

34. The friction experienced by a body, when in motion, is known as
A. Rolling friction
B. Dynamic friction
C. Limiting friction
D. Static friction
Answer : B

35. When trying to turn a key into a lock, following is applied
A. Coplanar force
B. Non-coplanar forces
C. Moment
D. Couple
Answer : D

36. The centre of gravity of a triangle lies at the point of
A. Concurrence of the medians
B. Intersection of its altitudes
C. Intersection of bisector of angles
D. Intersection of diagonals
Answer : A

37. The Cartesian equation of trajectory is (where u = Velocity of projection, ? = Angle of projection, and x, y = Co-ordinates of any point on the trajectory after t seconds.)
A. y = (gx²/2u² cos²?) + x. tan?
B. y = (gx²/2u² cos²?) - x. tan?
C. y = x. tan? - (gx²/2u² cos²?)
D. y = x. tan? + (gx²/2u² cos²?)
Answer : C

38. Tension in the cable supporting a lift is more when the lift is moving __________ with an acceleration.
A. Upwards
B. Downwards
C. Horizontal
D. None of these
Answer : A

39. A weight of 1000 N can be lifted by an effort of 80 N. If the velocity ratio is 20, the machine is
A. Reversible
B. Non-reversible
C. Ideal
D. None of these
Answer : A

40. The horizontal range of a projectile (R) is given by
A. R = u² cos2?/g
B. R = u² sin2?/g
C. R = u² cos?/g
D. R = u² sin?/g
Answer : B

41. The velocity ratio in case of an inclined plane inclined at angle ? to the horizontal and weight being pulled up the inclined plane by vertical effort is
A. sin?
B. cos?
C. tan?
D. cosec?
Answer : A

42. In actual machines, mechanical advantage is __________ velocity ratio.
A. Equalto
B. Less than
C. Greater than
D. None of these
Answer : B

43. Which of the following is a scalar quantity?
A. Force
B. Speed
C. Velocity
D. Acceleration
Answer : B

44. The law of the machine is (where P = Effort applied to lift the load, m = A constant which is equal to the slope of the line, W = Load lifted, and C = Another constant which represents the machine friction.)
A. P = mW - C
B. P = m/W + C
C. P = mW + C
D. P = C - mW
Answer : C

45. If the masses of both the bodies, as shown in the below figure, are reduced to 50 percent, then tension in the string will be
A. Same
B. Half
C. Double
D. None of these
Answer : B

46. The centre of percussion is below the centre of gravity of the body and is at a distance equal to
A. h/kG
B. h²/kG
C. kG²/h
D. h × kG
Answer : C

47. A flywheel on a motor goes from rest to 1000 rpm in 6 sec. The number of revolutions made is nearly equal to
A. 25
B. 50
C. 100
D. 250
Answer : B

48. The unit of power in S.I. units is
A. Horsepower
B. Joule
C. Watt
D. kg-m
Answer : C

49. The moment of inertia of a solid cone of mass m and base radius r about its vertical axis is
A. 3mr²/5
B. 3mr²/10
C. 2mr²/5
D. 4mr²/5
Answer : B

50. If a number of coplanar forces acting at a point be in equilibrium, the sum of clockwise moments must be __________ the sum of anticlockwise moments, about any point.
A. Equal to
B. Less than
C. Greater than
D. None of these
Answer : A