Question

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

• A. $\sqrt{MK}L$
• B. $\frac{K{L}^2}{2M}$
• C. Zero
• D. $\frac{M{L}^2}{K}$

Answer 1

Answer: (A)

$\sqrt{MK}L$

Maximum compression of the spring occurs when velocity of the block zero.
$\therefore$, equating PE of the spring with KE of the block, $\frac{1}{2}K{L}^2=\frac{p^2}{2M}$
$p=\sqrt{MK}L$