In the figure, the block B of mass m starts from rest at the top of a wedge W of mass M. All surfaces are without friction. W can slide on the ground. B slides down onto the ground, moves along it with a speed v, has an elastic collision with the wall, and climbs back two W.

Options

A. B will reach the top of W again
B. From the beginning, till the collision with the wall, the centre of mass of B plus W' does not move horizontally.
C. After the collision the centre of mass of B plus W' moves with the velocity `(2mv)/(m+M)`
D. When B reaches its highest position on W, the speed of W is `(2mv)/(m+W)`

Answer

B, C, D