A ball kept in a close 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

Options

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

B

Explanation

As no external force acts on the ball `+` box system, hence velcilty of the system remains constant.