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A ball is bouncing elastically with a sp...

A ball is bouncing elastically with a speed `1 m//s` between walls of a railway compartment of size `10 m` in a direction perpendicular to walls. The train is moving at a constant velocity of `10 m//s` parallel to the direction of motion of the ball. As seen from the ground, choose the correct option

A

(a) the direction os motion of the ball changes every ` 10 secends.

B

(b) speed of ball changes every ` 10 seconds`.

C

(c ) average speed of ball over any `20 second ` interval is fixed.

D

(d) the acceleration of ball is the same as from the train.

Text Solution

Verified by Experts

The correct Answer is:
B, C, D
Since the ball is moving with a very amll speed in the moving train, the direction of motion of the ball is the same as that of the train. The direction of motion of ball does not change with respect to observer on ground.
The speed of the ball s=as observed by observre on ground befre collidion with side of train is ` 10 + 1 = 11 m//s` and after elastic elastic collistion os ` 10 -1 = 9 m//s`.
Since the collision of the ball with side of reain is perfectly elastic, the total momentum and kinetic energy ar conserved. so averge speed of the ball over any ` 20` seconds interval is condtant as onserved by observe on ground. ltBrgt Since train is moving with constant velocity . if is an intertial frame. so acceleration of ball is same as from the train.
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