Engineering Mechanics 1000+ MCQ with answer for LIC ADO

1. The centre of percussion of the homogeneous rod of length L suspended at the top will be
A. L/2
B. L/3
C. 3L/4
D. 2L/3
Answer : D

2. Work done is said to be zero, when
A. Some force acts on a body, but displacement is zero
B. No force acts on a body but some displacement takes place
C. Either (A) or (B)
D. None of the above
Answer : C

3. 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

4. Two forces are acting at an angle of 120°. The bigger force is 40 N and the resultant is perpendicular to the smaller one. The smaller force is
A. 20 N
B. 40 N
C. 120 N
D. None of these
Answer : A

5. The maximum height of a projectile on a horizontal plane, is
A. u² sin²?/2g
B. u² cos²?/2g
C. u² sin²?/g
D. u² cos²?/g
Answer : A

6. A semicircular disc rests on a horizontal surface with its top flat surface horizontal and circular portion touching down. The coefficient of friction between semi circular disc and horizontal surface is ?. This disc is to be pulled by a horizontal force applied at one edge and it always remains horizontal. When the disc is about to start moving, its top horizontal force will
A. Remain horizontal
B. Slant up towards direction of pull
C. Slant down towards direction of pull
D. None of the above
Answer : C

7. A screw jack used for lifting the loads is
A. A reversible machine
B. A non-reversible machine
C. An ideal machine
D. None of these
Answer : B

8. The moment of inertia of a thin disc of mass m and radius r, about an axis through its centre of gravity and perpendicular to the plane of the disc is
A. mr²/2
B. mr²/4
C. mr²/6
D. mr²/8
Answer : A

9. The forces, which meet at one point, but their lines of action do not lie in a plane, are called
A. Coplanar non-concurrent forces
B. Non-coplanar concurrent forces
C. Non-coplanar non-concurrent forces
D. Intersecting forces
Answer : B

10. The product of either force of couple with the arm of the couple is called
A. Resultant couple
B. Moment of the forces
C. Resulting couple
D. Moment of the couple
Answer : D

11. If a number of forces are acting at a point, their resultant is given by
A. (?V)² + (?H)²
B. ?[(?V)² + (?H)²]
C. (?V)² +(?H)² +2(?V)(?H)
D. ?[(?V)² +(?H)² +2(?V)(?H)]
Answer : B

12. 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

13. Centre of gravity of a solid cone lies on the axis at the height
A. One fourth of the total height above base
B. One third of the total height above base
C. One-half of the total height above base
D. Three eighth of the total height above the base
Answer : A

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

15. Lami's theorem states that
A. Three forces acting at a point will be in equilibrium
B. Three forces acting at a point can be represented by a triangle, each side being proportional to force
C. If three forces acting upon a particle are represented in magnitude and direction by the sides of a triangle, taken in order, they will be in equilibrium
D. If three forces acting at a point are in equilibrium, each force is proportional to the sine of the angle between the other two
Answer : D

16. The centre of gravity of a semi-circle lies at a distance of __________ from its base measured along the vertical radius.
A. 3r/ 8
B. 4r/ 3?
C. 8r/3
D. 3r/4?
Answer : B

17. The total momentum of a system of masses (i. e. moving bodies) in any one direction remains constant, unless acted upon by an external force in that direction. This statement is called
A. Newton's first law of motion
B. Newton's second law of motion
C. Principle of conservation of energy
D. Principle of conservation of momentum
Answer : D

18. A circular hole of 50 mm diameter is cut out from a circular disc of 100 mm diameter as shown in the below figure. The centre of gravity of the section will lie
A. In the shaded area
B. In the hole
C. At O
D. None of these
Answer : A

19. The point, through which the whole weight of the body acts, irrespective of its position, is known as
A. Moment of inertia
B. Centre of gravty
C. Centre of percussion
D. Centre of mass
Answer : B

20. The maximum frictional force which comes into play when a body just begins to slide over another surface is called
A. Limiting friction
B. Sliding friction
C. Rolling friction
D. Kinematic friction
Answer : A

21. Kinetic friction is the
A. Tangent of angle between normal reaction and the resultant of normal reaction and the limiting friction
B. Ratio of limiting friction and normal reaction
C. The friction force acting when the body is just about to move
D. The friction force acting when the body is in motion
Answer : D

22. According to the law of moments, if a number of coplanar forces acting on a particle are in equilibrium, then
A. Their algebraic sum is zero
B. Their lines of action are at equal distances
C. The algebraic sum of their moments about any point in their plane is zero
D. The algebraic sum of their moments about any point is equal to the moment of their resultant force about the same point.
Answer : C

23. The maximum acceleration of a particle moving with simple harmonic motion is
A. ?
B. ?r
C. ?²r
D. ?/r
Answer : C

24. When the spring of a watch is wound, it will possess
A. Strain energy
B. Kinetic energy
C. Heat energy
D. Electrical energy
Answer : A

25. A force while acting on a body may
A. Change its motion
B. Balance the forces, already acting on it
C. Give rise to the internal stresses in it
D. All of these
Answer : D

26. The efficiency of a screw jack is maximum, when (where ? = Helix angle, and ? = Angle of friction.)
A. ? = 45° + ?/2
B. ? = 45° - ?/2
C. ? = 90° + ?
D. ? = 90° - ?
Answer : B

27. The velocity ratio of a first system of pulleys with 4 pulleys is
A. 4
B. 8
C. 16
D. 20
Answer : C

28. If a rigid body is in equilibrium under the action of three forces, then
A. These forces are equal
B. The lines of action of these forces meet in a point
C. The lines of action of these forces are parallel
D. Both (B) and (C) above
Answer : D

29. Which of the following statement is correct?
A. The kinetic energy of a body during impact remains constant.
B. The kinetic energy of a body before impact is equal to the kinetic energy of a body after impact.
C. The kinetic energy of a body before impact is less than the kinetic energy of a body after impact.
D. The kinetic energy of a body before impact is more than the kinetic energy of a body after impact.
Answer : D

30. The angle which an inclined plane makes with the horizontal when a body placed on it is about to move down is known as angle of
A. Friction
B. Limiting friction
C. Repose
D. Kinematic friction
Answer : C

31. The coefficient of friction depends upon
A. Nature of surfaces
B. Area of contact
C. Shape of the surfaces
D. All of the above
Answer : A

32. The rate of change of displacement of a body is called
A. Velocity
B. Acceleration
C. Momentum
D. None of these
Answer : A

33. If the resultant of two equal forces has the same magnitude as either of the forces, then the angle between the two forces is
A. 30°
B. 60°
C. 90°
D. 120°
Answer : D

34. Moment of inertia of a triangular section of base (b) and height (h) about an axis passing through its vertex and parallel to the base, is __________ than that passing through its C.G. and parallel to the base.
A. Nine times
B. Six times
C. Four times
D. Two times
Answer : A

35. The motion of a particle round a fixed axis is
A. Translatory
B. Rotary
C. Circular
D. Translatory as well as rotary
Answer : C

36. Which of the following is the locus of a point that moves in such a manner that its distance from a fixed point is equal to its distance from a fixed line multiplied by a constant greater than one
A. Ellipse
B. Hyperbola
C. Parabola
D. Circle
Answer : B

37. The linear velocity of a body rotating at ? rad/s along a circular path of radius r is given by
A. ?/r
B. ?.r
C. ?²/r
D. ?².r
Answer : B

38. In order to completely specify angular displacement by a vector, it must fix
A. Direction of the axis of rotation
B. Magnitude of angular displacement
C. Sense of angular displacement
D. All of these
Answer : D

39. The overturning of a vehicle on a level circular path can be avoided if the velocity of vehicle is __________ ?(gra/h)
A. Less than
B. Greater than
C. Equal to
D. None of these
Answer : A

40. 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

41. Center of percussion is
A. The point of C.G.
B. The point of metacenter
C. The point of application of the resultant of all the forces tending to cause a body to rotate about a certain axis
D. Point of suspension
Answer : C

42. The velocity ratio for the first system of pulleys is (where n is the number of pulleys.)
A. n
B. n²
C. 2n
D. 2n - 1
Answer : C

43. Mass moment of inertia of a uniform thin rod of mass M and length (l) about its mid-point and perpendicular to its length is
A. (2/3) Ml²
B. (1/3) Ml²
C. (3/4) Ml²
D. (1/12) Ml²
Answer : D

44. The centre of gravity a T-section 100 mm × 150 mm × 50 mm from its bottom is
A. 50 mm
B. 75 mm
C. 87.5 mm
D. 125 mm
Answer : C

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

46. Which of the following statement is incorrect?
A. A force acting in the opposite direction to the motion of the body is called force of friction
B. The ratio of the limiting friction to the normal reaction is called coefficient of friction
C. A machine whose efficiency is 100% is known as an ideal machine
D. The velocity ratio of a machine is the ratio of load lifted to the effort applied
Answer : D

47. 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

48. A pair of smith's tongs is an example of the lever of
A. Zeroth order
B. First order
C. Second order
D. Third order
Answer : C

49. The resultant of two equal forces P making an angle ?, is given by
A. 2P sin?/2
B. 2P cos?/2
C. 2P tan?/2
D. 2P cot?/2
Answer : B

50. In the shown figure, the tension (T) in the string will be
A. m?. m?. g/(m? + m?)
B. 2m?. m?. g/(m? + m?)
C. (m? + m?)/ m?. m?. g
D. (m? + m?)/2m?. m?. g
Answer : B