SSC CPO - Engineering Mechanics 1000+ MCQ [Solved] PDF Download

1. Three forces acting on a rigid body are represented in magnitude, direction and line of action by the three sides of a triangle taken in order. The forces are equivalent to a couple whose moment is equal to
A. Area of the triangle
B. Twice the area of the triangle
C. Half the area of the triangle
D. None of these
Answer : B

2. Moment of inertia of a rectangular section having width (b) and depth (d) about an axis passing through its C.G. and parallel to the width (b), is
A. db³/12
B. bd³/12
C. db³/36
D. bd³/36
Answer : B

3. The resultant of the two forces P and Q is R. If Q is doubled, the new resultant is perpendicular to P. Then
A. P = Q
B. Q = R
C. Q = 2R
D. None of these
Answer : B

4. Moment of inertia of a circular section about its diameter (d) is
A. ?d³/16
B. ?d³/32
C. ?d⁴/32
D. ?d⁴/64
Answer : D

5. The matter contained in a body, is called
A. Impulsive force
B. Mass
C. Weight
D. Momentum
Answer : B

6. 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

7. The moment of inertia of a solid sphere of mass m and radius r is
A. 2mr²/3
B. 2mr²/5
C. mr²
D. mr²/2
Answer : B

8. 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

9. The moment of inertia of a solid cylinder of mass m, radius r and length l about the longitudinal axis or polar axis is
A. mr²/2
B. mr²/4
C. mr²/6
D. mr²/8
Answer : A

10. 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

11. 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

12. In order to double the period of simple pendulum, the length of the string should be
A. Halved
B. Doubled
C. Quadrupled
D. None of these
Answer : C

13. Pick up the incorrect statement from the following:
A. The C.G. of a circle is at its centre
B. The C.G. of a triangle is at the intersection of its medians
C. The C.G. of a rectangle is at the intersection of its diagonals
D. The C.G. of a semicircle is at a distance of r/2 from the centre
Answer : D

14. In a framed structure, as shown in the below figure, the force in the member AB is __________ the force in member AC.
A. Half
B. Equal to
C. Double
D. None of these
Answer : A

15. 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

16. A body of mass m moving with a constant velocity v strikes another body of same mass moving with same velocity but in opposite direction. The common velocity of both the bodies after collision is
A. v
B. 2v
C. 4v
D. 8v
Answer : B

17. 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

18. The forces which meet at one point, but their lines of action __________ on the same plane, are Known as non-coplanar concurrent forces.
A. Lie
B. Do not lie
C. Either A or B
D. None of these
Answer : B

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

20. When a body of mass moment of inertiaI (about a given axis) is rotated about that axis with an angular velocity to, then the kinetic energy of rotation is
A. I?
B. I?²
C. 0.5 I?
D. 0.5 I?²
Answer : D

21. 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

22. The force applied on a body of mass 100 kg to produce an acceleration of 5 m/s², is
A. 20 N
B. 100 N
C. 500 N
D. None of these
Answer : C

23. 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

24. Which of the following is not the unit of distance?
A. Angstrom
B. Light year
C. Micron
D. Milestone
Answer : D

25. 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

26. 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

27. In the shown figure, if the angle of inclination of the plane is increased, then acceleration of the system will
A. Increase
B. Decrease
C. Remain the same
D. None of these
Answer : B

28. If the number of pulleys in a system is equal to its velocity ratio, then it is a __________ system of pulleys
A. First
B. Second
C. Third
D. None of these
Answer : B

29. The maximum efficiency of a lifting machine is
A. 1/m
B. V.R./m
C. m/V.R.
D. 1/(m × V.R.)
Answer : D

30. The time of flight (t) of a projectile on an upward inclined plane is (where u = Velocity of projection, ? = Angle of projection, and ? = Inclination of the plane with the horizontal.)
A. t = g cos ?/2u sin (? - ?)
B. t = 2u sin (? - ?)/g cos ?
C. t = g cos ?/2u sin (? + ?)
D. t = 2u sin (? + ?)/g cos ?
Answer : B

31. The amplitude is always __________ radius of the circle.
A. Equal to
B. Less than
C. Greater than
D. None of these
Answer : A

32. 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

33. 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

34. The efficiency of a lifting machine is the ratio of
A. Output to the input
B. Work done by the machine to the work done on the machine
C. Mechanical advantage to the velocity ratio
D. All of the above
Answer : D

35. According to Newton's first law of motion,
A. Everybody continues in its state of rest or of uniform motion, in a straight line, unless it is acted upon by some external force
B. The rate of change of momentum is directly proportional to the impressed force, and takes place in the same direction, in which the force acts
C. To every action, there is always an equal and opposite reaction
D. None of the above
Answer : A

36. For any system of coplanar forces, the condition of equilibrium is that the
A. Algebraic sum of the horizontal components of all the forces should be zero
B. Algebraic sum of the vertical components of all the forces should be zero
C. Algebraic sum of moments of all the forces about any point should be zero
D. All of the above
Answer : D

37. 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

38. The coefficient of friction depends on
A. Area of contact
B. Shape of surfaces
C. Strength of surfaces
D. Nature of surface
Answer : D

39. 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

40. 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

41. In he 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

42. 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

43. When a person, on a bicycle, drives round a curve, he has to lean __________ to maintain equilibrium.
A. Inward
B. Outward
C. Towards front
D. Towards back
Answer : A

44. The angular velocity (in rad/s) of a body rotating at N revolutions per minute is
A. ?N/60
B. ?N/180
C. 2?N/60
D. 2?N/180
Answer : C

45. 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 gravity
C. Centre of percussion
D. Centre of mass
Answer : B

46. The periodic time of one oscillation for a simple pendulum is (where l = Length of the pendulum.)
A. (1/2?). ?(l/g)
B. (1/2?). ?(g/l)
C. 2?. ?(l/g)
D. None of these
Answer : C

47. 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

48. 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

49. Which of the following is not the unit of power?
A. kW (kilowatt)
B. hp (horse power)
C. kcal/sec
D. kcal/kg sec
Answer : D

50. The motion of a wheel of a car is
A. Purely translation
B. Purely rotational
C. Combined translation and rotational
D. None of these
Answer : C