Two blocks `M_(1) and M_(2)` having equal mass are free to move on a horizontal frictionless surface . `M_(2)` is attached to a massless spring as shown in figure .Intially `M_(2)` is at rest and `M_(1)` is moving toward `M_(2)` with speed v and collides head - on with `M_(2)` .

Options

A. While spring is fully compressed all the KE of `M_(1)` is stored as PE of spring .
B. While spring fully compressed the system momentum is not conserved ,through final momentum is equal to intial momentum .
C. If spring surface on which blocksare moving has friction , then collision cannot be elastic
D. If the surface o which blocks are moving has friction ,then collision cannot be elastic

Answer

C

Explanation

When `m_(1)` comes in contact with `M_(2),M_(1)` is retarded and `M_(2)` is accelerated .
(A) The spring will continue to compress until the two blocks acquire will be conserved .
(C ) Is spring is massless whole energy of `M_(1)` will be impared to `M_(2) and M_(1)` will be at rest , then
(D) Collision is inelastic ,even if friction is not involved .