A block of mass `m` slides down a wedge of mass `M` as shown . The whole system is at rest , when the height of the block is `h` above the ground. The wedge surface is smooth and gradually flattens. There is no friction between wedge and ground.

If there would have been friction wedge and block , which of the following quantities would still remains conserved ?

Options

A. Linear momentum of the system along horizontal direction
B. Linear momentum of the system along vertical direction
C. Linear momentum of the system along a tangent to the curved surface of the wedge
D. Mechanical energy of the system

Answer

A

Explanation

Linear momentum is conserved only in horizontal direction.
Net `F_(ext)` on system is zero in horizontal direction therefore linear momentum is conserved only in horizontal direction.