Q: A ball is bouncing elastically with as 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.

(a) The direction of motion of the ball changes every 10.

(b) Speed of ball changes every 10

(c) Average speed of ball over any 20 interval is fixed

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

Ans: (b) , (c) & (d)