Engineering Mechanics online - Set 21 - ObjectiveBooks
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# Practice Test: Question Set - 21

1. If u1 and u2 are the velocities of two moving bodies in the same direction before impact and v1 and v2 are their velocities after impact, then coefficient of restitution is given by
(A) (v1 - v2)/(u1 - u2)
(B) (v₂ - v₁)/(u1 - u2)
(C) (u1 - u2)/(v1 - v2)
(D) (u₂ + u₁)/(v₂ + v₁)

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

3. The range of projectile on a downward inclined plane is ________ the range on upward inclined plane for the same velocity of projection and angle of projection.
(A) Less than
(B) More than
(C) Equal to
(D) None of These

4. The point, through which the whole weight of the body acts, irrespective of its position, is known as
(A) Moment of inertia
(B) Center of gravity
(C) Center of percussion
(D) Center of mass

5. The total energy possessed by a system of moving bodies
(A) Is constant at every instant
(B) Varies from point to point
(C) Is maximum in the start and minimum at the end
(D) Is minimum in the start and maximum at the end

6. The acceleration of a body sliding down an inclined surface is
(A) g sinθ
(B) g cosθ
(C) g tanθ
(D) None of these

7. 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

8. A machine having an efficiency less than 50%, is known as
(A) Reversible machine
(B) Non-reversible machine
(C) Neither reversible nor non-reversible machine
(D) Ideal machine

9. Static friction is always __________ dynamic friction.
(A) Equal to
(B) Less than
(C) Greater than
(D) None of these

10. In the shown figure, the tension (T) in the string will be

(A) m₁. m₂. g/(m₁ + m₂)
(B) 2m₁. m₂. g/(m₁ + m₂)
(C) (m₁ + m₂)/ m₁. m₂. g
(D) (m₁ + m₂)/2m₁. m₂. g

11. A body of weight 'W' is required to move up on rough inclined plane whose angle of inclination with the horizontal is 'α'. The effort applied parallel to the plane is given by (where μ = tanφ = Coefficient of friction between the plane and the body.)
(A) P = W tanα
(B) P = W tan (α + φ)
(C) P = W (sinα + μcosα)
(D) P = W (cosα + μsinα)

12. A smooth cylinder lying on a __________ is in neutral equilibrium.
(A) Curved surface
(B) Convex surface
(C) Horizontal surface
(D) None of these

13. The unit of energy in S.I. units is
(A) Dyne
(B) Watt
(C) kg-m
(D) Joule

14. A ladder is resting on a rough ground and leaning against a smooth vertical wall. The force of friction will act
(A) Downward at its upper end
(B) Upward at its upper end
(C) Zero at its upper end
(D) Perpendicular to the wall at its upper end

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

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