A long plank of mass M is initially at rest on a frictionless surface. A small block with mass m and initial speed `u_(0)` slides on top of the larger plank. The coefficient of friction between the block and plank is `mu`
Net work done by friction if the top block falls off the plank after sliding over its length L is
A. `- mumgL`
B. `-mu((M+m)/(M))gL`
C. `-mu((M)/(M+m))gL`
D. `-mu MgL`
