DRDO - Engineering Mechanics 1000+ MCQ [Solved] PDF Download

1. 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

2. A pendulum which executes one beat per second is known as
A. Simple pendulum
B. Compound pendulum
C. Torsional pendulum
D. Second's pendulum
Answer : D

3. The unit of force in S.I. units is
A. kilogram
B. Newton
C. Watt
D. Dyne
Answer : B

4. If a number of forces act simultaneously on a particle, it is possible
A. Not a replace them by a single force
B. To replace them by a single force
C. To replace them by a single force through C.G.
D. To replace them by a couple
Answer : B

5. In order to determine the effects of a force, acting on a body, we must know
A. Magnitude of the force
B. Line of action of the force
C. Nature of the force i.e. whether the force is push or pull
D. All of the above
Answer : D

6. Varingon's theorem of moments states that 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 : D

7. 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

8. The acceleration of a body sliding down an inclined surface is
A. g sin?
B. g cos?
C. g tan?
D. None of these
Answer : A

9. The velocity of a body on reaching the ground from a height h, is
A. 2.?(gh)
B. ?(gh)
C. ?(2gh)
D. 2g.?h
Answer : C

10. 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

11. The maximum mechanical advantage of a lifting machine is
A. 1 + m
B. 1 - m
C. 1 / m
D. m
Answer : C

12. A block of mass 20 kg lying on a rough horizontal plane is connected by a light string passing over a smooth pulley to another mass 5 kg, which can move freely in the Vertical direction, as shown in the below figure. The tension in the string will __________ with the increase in coefficient of friction.
A. Increase
B. Decrease
C. Not be effected
D. None of these
Answer : A

13. The angle between two forces when the resultant is maximum and minimum respectively are:
A. 0° and 180°
B. 180° and 0°
C. 90° and 180°
D. 90° and 0°
Answer : A

14. 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

15. The acceleration of a particle moving with simple harmonic motion is __________ at the mean position.
A. Zero
B. Minimum
C. Maximum
D. None of these
Answer : A

16. If three forces acting in different planes can be represented by a triangle, these will be in
A. Non-equilibrium
B. Partial equilibrium
C. Full equilibrium
D. Unpredictable
Answer : A

17. 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

18. The law of motion involved in the recoil of gun is
A. Newton's first law of motion
B. Newton's second law of motion
C. Newton's third law of motion
D. None of these
Answer : C

19. If P is the force acting on the body, m is the mass of the body and a is the acceleration of the body, then according to Newton's second law of motion,
A. P + m.a = 0
B. P - m.a = 0
C. P × m.a = 0
D. P/m.a = 0
Answer : B

20. The periodic time of a particle with simple harmonic motion is __________ proportional to the angular velocity.
A. Directly
B. Inversely
C. Square root
D. None of these
Answer : B

21. 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

22. The moment of inertia of a square of side a about its diagonal is
A. a²/8
B. a³/12
C. a⁴/12
D. a⁴/16
Answer : C

23. The centre of gravity of a quadrant of a circle lies along its central radius (r) at a distance of
A. 0.5r
B. 0.6 r
C. 0.7 r
D. 0.8 r
Answer : B

24. If three forces acting in one plane upon a rigid body, keep it in equilibrium, then they must either
A. Meet in a point
B. Be all parallel
C. At least two of them must meet
D. All the above are correct
Answer : D

25. 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

26. A force is completely defined when we specify
A. Magnitude
B. Direction
C. Point of application
D. All of the above
Answer : D

27. If the body falls freely under gravity, then the gravitational acceleration is taken as
A. +8.9 m/s²
B. -8.9 m/s²
C. +9.8 m/s²
D. -9.8 m/s²
Answer : C

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

29. A smooth cylinder lying on its convex surface remains in __________ equilibrium.
A. Stable
B. Unstable
C. Neutral
D. None of these
Answer : B

30. The velocity of a particle (v) moving with simple harmonic motion, at any instant is given by (where r = Amplitude of motion, and y = Displacement of the particle from mean position.)
A. ?.?(y² - r²)
B. ?.?(r² - y²)
C. ?².?(y² - r²)
D. ?².?(r² - y²)
Answer : B

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

32. If a given force (or a given system of forces) acting on a body __________ the position of the body, but keeps it in equilibrium, then its effect is to produce internal stress in the body.
A. Change
B. Does not change
C. Changes periodically
D. None of these
Answer : B

33. The velocity ratio of a differential wheel and axle with D as the diameter of effort wheel and d1 and d2 as the diameters of larger and smaller axles respectively, is
A. D/(d? + d?)
B. D/(d? - d?)
C. 2D/(d? + d?)
D. 2D/(d? - d?)
Answer : D

34. According to parallel axis theorem, the moment of inertia of a section about an axis parallel to the axis through centre of gravity (i.e. I_P) is given by(where, A = Area of the section, I_G = Moment of inertia of the section about an axis passing through its C.G., and h = Distance between C.G. and the parallel axis.)
A. I_P = I_G + Ah²
B. I_P = I_G - Ah²
C. I_P = I_G / Ah²
D. I_P = Ah² / I_G
Answer : A

35. Which of the following is an equation of linear motion? (where, u and v = Initial and final velocity of the body, a = Acceleration of the body, and s = Displacement of the body in time t seconds.)
A. v = u + a.t
B. s = u.t + ½ a.t²
C. v² = u² + 2a.s
D. All of these
Answer : D

36. 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

37. The unit of moment of inertia of an area is
A. kg-m²
B. kg-m-s²
C. kg/m²
D. m⁴
Answer : D

38. 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

39. On the ladder resting on the ground and leaning against a smooth vertical wall, the force of friction will be
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
Answer : D

40. A particle moves along a straight line such that distance (x) traversed in t seconds is given by x = t² (t - 4), the acceleration of the particle will be given by the equation
A. 6t² - 8t
B. 3t² + 2t
C. 6f - 8
D. 6f - 4
Answer : C

41. The velocity ratio of a differential pulley block with D and d as the diameters of larger and smaller pulley, is A. D/(D - d)
B. D/(D + d)
C. 2D/(D - d)
D. 2D/(D + d)
Answer : C

42. If a suspended body is struck at the centre of percussion, then the pressure on die axis passing through the point of suspension will be
A. Maximum
B. Minimum
C. Zero
D. Infinity
Answer : C

43. Tangent of angle of friction is equal to
A. Kinetic friction
B. Limiting friction
C. Angle of repose
D. Coefficient of friction
Answer : D

44. The maximum efficiency of a screw jack is
A. (1 - sin?)/(1 + sin?)
B. (1 + sin?)/(1 - sin?)
C. (1 - tan?)/(1 + tan?)
D. (1 + tan?)/(1 - tan?)
Answer : A

45. According to principle of moments
A. If a system of coplanar forces is in equilibrium, then their algebraic sum is zero
B. If a system of coplanar forces is in equilibrium, then the algebraic sum of their moments about any point in their plane is zero
C. The algebraic sum of the moments of any two forces about any point is equal to moment of the resultant about the same point
D. Positive and negative couples can be balanced
Answer : B

46. Limiting force of friction is the
A. Tangent of angle between normal reaction and the resultant of normal reaction and 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 : C

47. A cable with a uniformly distributed load per horizontal meter run will take the following shape
A. Straight line
B. Parabola
C. Hyperbola
D. Elliptical
Answer : B

48. A machine having an efficiency greater than 50%, is known as
A. Reversible machine
B. Non-reversible machine
C. Neither reversible nor non-reversible machine
D. Ideal machine
Answer : A

49. 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

50. The power developed by a body acted upon by a torque T Newton metre (N - m) and revolving at ? radian/s is given by
A. T.? (in watts)
B. T.?/60 (in watts)
C. T.?/75 (in kilowatts)
D. T.?/4500 (in kilowatts)
Answer : A