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 `(l_(0))/4`. The coefficient of friction between each block and the surface (assuming it to be same between any of the blocks and the surface) is :

Options

A. `(Kl_(0))/(40 mg)`
B. `(Kl_(0))/(8 mg)`
C. `(3 Kl_(0))/( 8 mg)`
D. `17/20 (Kl_(0))/(mg)`

Explanation

Work energy theoram,
`-mu g(l_(0)+(l_(0))/4)=1/2K((l_(0))/4)^(2)-1/2Kl_(0)^(2) mu=(3Kl_(0))/(8 mg)`