two balls of 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 ?Why they move with the same speed ?Give reasons for your answer .

Answer 1

The balls were moving when the train was moving. So when the train brakes are applied, the balls keep moving forward.

Exactly what does Newtons first law of motion state?

http://www.physicsclassroom.com/class/newtlaws/u2l1a.cfm