Question

A block of mass $m$ rests on a stationary wedge of mass $M$. The wedge can slide freely on a smooth horizontal surface as shown in figure. If the block starts from rest, then:

• A. The position of the centre of mass of the system will change
• B. The position of the centre of mass of the system will change along the vertical but not along the horizontal
• C. The total energy of the system will remain constant
• D. All of the above

Answer 1

Answer: (D)

All of the above

Since there is external force in the horizontal direction, COM will have no acceleration horizontally.
Initially, both wedge and block are at rest, COM is at rest.
From momentum conservation, COM will remain at rest.
There is external force in the vertical direction, hence, COM will move in this direction. Option (B) is correct.
Option(A) is correct, since COM will move in the vertical direction.
Option(C) is correct since there are no dissipative forces like friction.
Hence, all of the options are correct.