Question

A ball kept in a closed box moves in the box making collisions with the walls. The box is kept on a smooth surface. The velocity of the centre of mass

• A. Of the box remains constant
• B. Of the (box + ball) system remains constant
• C. Of the ball remains constant
• D. Of the ball relative to the box remains constant

Answer 1

The correct option is B Of the (box + ball) system remains constant

As no external force acts on the (ball + box) system, hence velocity of the system remains constant.