Question

Two blocks each of mass $m$ are joined together using an ideal spring of force constant $K$ and natural length $l_0$. The blocks are touching each other when the system is released from rest on a rough horizontal surface. Both the blocks come to rest simultaneously when the extension in the spring is $\frac{l_0}{4}$. Find the coefficient of friction between each block and the surface. (Assume $\mu$ to be same for both blocks and surface)

Answer 1

Extension $x=l/4$

Therefore

$kx=frkl/4=\mu mg\mu =\frac{kl}{4mg}$