### Multiple Choice Questions and Answers (MCQs) on Engineering Mechanics

01. 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

02. The bellow figure shows the three coplanar forces P, Q and R acting at a point O. If these forces are in equilibrium, then

(A) P/sin β = Q/sin α = R/sin ɣ
(B) P/sin α = Q/sin β = R/sin ɣ
(C) P/sin ɣ = Q/sin α = R/sin β
(D) P/sin α = Q/sin ɣ = R/sin β

03. 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

04. The angle of inclination of the plane at which the body begins to move down the plane, is called

(A) Angle of friction
(B) Angle of repose
(C) Angle of projection
(D) None of these

05. Pick up wrong statement about friction force for dry surfaces. Friction force is

(A) Proportional to normal load between the surfaces
(B) Dependent on the materials of contact surface
(C) Proportional to velocity of sliding
(D) Independent of the area of contact surfaces

06. The term ‘Centroid’ is

(A) The same as centre of gravity
(B) The point of suspension
(C) The point of application of the resultant of all the forces tending to cause a body to rotate about a certain axis
(D) None of the above

07. The C.G. of a plane lamina will not be at its geometrical centre in the case of a

(A) Right angled triangle
(B) Equilateral triangle
(C) Square
(D) Circle

08. 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

09. 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

10. Forces are called coplanar when all of them acting on body lie in

(A) One point
(B) One plane
(C) Different planes
(D) Perpendicular planes

11. 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

12. 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

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

14. The periodic time (T) is given by (where, ω = Angular velocity of particle in rad/s.)

(A) ω/2π
(B) 2π/ω
(C) 2π × ω
(D) π/ω

15. The resultant of two forces P and Q (such that P > Q) acting along the same straight line, but in opposite direction, is given by

(A) P + Q
(B) P – Q
(C) P / Q
(D) Q / P

16. When two elastic bodies collide with each other,

(A) The two bodies will momentarily come to rest after collision
(B) The two bodies tend to compress and deform at the surface of contact
(C) The two bodies begin to regain their original shape
(D) All of the above

17. The coefficient of friction depends upon

(A) Nature of surfaces
(B) Area of contact
(C) Shape of the surfaces
(D) All of the above

18. The angular velocity (in rad/s) of a body rotating at N revolutions per minute is

(A) πN/60
(B) πN/180
(C) 2πN/60
(D) 2πN/180

19. A block of mass m1, placed on an inclined smooth plane is connected by a light string passing over a smooth pulley to mass m2, which moves vertically downwards as shown in the below figure. The tension in the string is

(A) m1/m2
(B) m1. g. sin α
(C) m1.m2/m1 + m2
(D) m1. m2.g (1 + sin α)/(m1 + m2)

20. 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

21. 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

22. The algebraic sum of moments of the forces forming couple about any point in their plane is

(A) Equal to the moment of the couple
(B) Constant
(C) Both of above are correct
(D) Both of above are wrong

23. In the lever of third order, load ‘W’, effort ‘P’ and fulcrum ‘F’ are oriented as follows

(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

24. Which of the following statement is correct?

(A) The algebraic sum of the forces, constituting the couple is zero
(B) The algebraic sum of the forces, constituting the couple, about any point is the same
(C) A couple cannot be balanced by a single force but can be balanced only by a couple of opposite sense
(D) All of the above