MCQ
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. Initially $M _2$ is at rest and $M _1$ is moving toward $M _2$ with speed $v$ and collides head$-$on with $M _2$.


- AWhile spring is fully compressed all the $KE$ of $M_1$ is stored as $PE$ of spring.
- BIf the surface on which blocks are moving has friction, then collision cannot be elastic.
- CIf spring is massless, the final state of the $M_1$ is state of rest.
- ✓Both $B$ and $C$

