Answer to Question #169220 in Physics for Tiny

Question

Two balls of the same size but of different material, rubber and iron are kept on the smooth floor of a moving train. The brakes are applied suddenly to stop the train. Will the balls start rolling? If so, in which direction? Will they move with the same speed? Give reason for your answer.

Answer 1

The balls will start rolling because they have a mass and they will try to continue their motion according to Newton's first law.

They will roll in the direction of train's motion. They will move at the same speed if they are on a smooth surface because they will just try to keep their initial speed of motion that is equal to the speed of the train before it started decelerating.