Q. 14

# Two billiard balls A and B, each of mass 50g and moving in opposite directions with speed of 5m s^{-1} each, collide and rebound with the same speed. If the collision lasts for 10^{-3} s, which of the following statements are true?

A. The impulse imparted to each ball is 0.25 kg m s^{-1} and the force on each ball is 250 N.

B. The impulse imparted to each ball is 0.25 kg m s^{-1} and the force exerted on each ball is 25 × 10^{-5} N.

C. The impulse imparted to each ball is 0.5 Ns.

D. The impulse and the force on each ball are equal in magnitude and opposite in direction.

Answer :

Given that speed of each ball v=5 m/s and mass of each ball m=0.005 kg.

So initial momentum of each ball

⇒

The direction of the velocity of each ball is reversed after the collision so final momentum of each ball

⇒

So from above result it is obvious that option (d) is correct.

As we know change in momentum of each ball is equal to impulse imparted to each ball

⇒

⇒

⇒

So from here we can say options (a) and (b) are wrong and option (d) is correct.

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