Two balls of the same size but of different materials,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 reasons for your answer.

(N/A) Yes,the balls will start rolling in the direction in which the train was moving.
Due to the application of the brakes,the train comes to rest,but due to the property of inertia,the balls try to remain in their state of motion; therefore,they begin to roll forward.
Since the masses of the rubber and iron balls are different,their inertia of motion is different.
Consequently,the inertial forces acting on them are not the same,and they will move with different speeds.