The block of mass M nbsp; moving on the

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The block of mass $M$  moving on the frictionless horizontal surface collides with the spring of spring constant $K$ and compresses it by length $L$. The maximum momentum of the block after collision is

A

Zero

B

$\frac{{M{L^2}}}{K}$

C

$\sqrt {MK} \,L$

D

$\frac{{K{L^2}}}{{2M}}$

The block of mass $M$  moving on the frictionless horizontal surface collides with the spring of spring constant $K$ and compresses it by length $L$. The maximum momentum of the block after collision is

When block of mass $M$  collides with the spring its kinetic energy gets converted into elastic potential energy of the spring.
From the law of conservation of energy
$\frac{1}{2}M{v^2} = \frac{1}{2}K{L^2}$ $\therefore $ $v = \sqrt {\frac{K}{M}} L$
Where $ v$  is the velocity of block by which it collides with spring. So, its maximum momentum
$P = Mv = M\sqrt {\frac{K}{M}} \,L$ = $\sqrt {MK} \,L$
After collision the block will rebound with same linear momentum.