Page 71 - CITS - WCS - Mechanical

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c. 0.5 mg
d. 5 mg
Answer: (a) 0.5 g
Explanation: Given, velocity, v = 5 m/s = 500 cm/s, momentum, p = 250 g cm/s, mass, m =?
We know that, momentum of a body is given by p = mv
or, m = p/v = 250/500 = 0.5 g
7. Which of the following is true about force?
a. Force is invisible
b. Force can move a body

c. It can deform a body
d. All of the above
Answer: (d) all of the above
Explanation: All of the given points are true for force.
8. A goalkeeper in a football game pulls his hands backwards after holding the ball shot at the goal. This enables
the goalkeeper to

a. increase the rate of change of momentum
b. decrease the rate of change of momentum
c. increase the force exerted by the balls on the hands
d. exert larger force on the ball
Answer: (b) decrease the rate of change of momentum
Explanation: A goalkeeper in a football game pulls his hands backwards after holding the ball shot at the goal,
enabling the goalkeeper to decrease the rate of change of momentum.
9.Which law is also known as the law of inertia?
a. Newton’s first law of motion
b. Newton’s second law of motion
c. Newton’s third law of motion
d. Law of conservation of momentum
Answer: (a) Newton’s first law of motion
Explanation: The inertia of a body is the tendency to not change its static or motional state. Newton’s first law of
motion says that a static body will remain motionless, and a body in motion will stay in motion until a force acts on
it. Therefore, Newton’s first law is associated with inertia and is also known as the law of inertia.
10. A passenger in a moving train tosses a coin that falls behind him. It means that the motion of the train is

a. uniform
b. accelerated
c. retarded
d. along circular tracks
Answer: (b) accelerated
Explanation: A passenger in a moving train tosses a coin that falls behind him. It means that the motion of the
train is accelerated.

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CITS : WCS - Mechanical - Exercise 4