Answer the following in brief:
 
Imagine a rubber ball and an iron ball of equal size placed on the smooth floor inside a moving train. If the train is stopped suddenly by applying the brakes, predict the behaviour of the balls. Explain your answer using the concept of inertia
 
, the balls  rolling in the direction in which the train was moving.
 
This is because, after applying the brakes, train  but the balls  due to inertia.
 
Since the mass between two balls is not the same, the inertia of the iron ball is  than the inertia of the rubber ball.
 
Hence, rubber ball rolls  than the iron ball.