A block of mass `1kg` is pushed on a non-movable wedge of mass `2kg` and height `h=30cm` with a velocity `u=6m//sec`. Before striking the wedge it travels `2m` on a rough horizontal portion. Velocity is just sufficient for the block to reach the top of the wedge. Assuming all surfaces are smooth except the given horizontal part and collision of block and wedge is jerkless, the friction coefficition of the rough horizontal part is `:`

Options

A. `0.125`
B. `0.377`
C. `0.675`
D. `0.45`

Answer

C

Explanation

velocity of the block after passing through the rough surface is `v=sqrt(36+2mug(2))=sqrt(36-40mu)`
Apply work energy theorem
`mu mg (2)+mgh=KE_(i)-KE_(f) ...(1)`
at the highest point
`V_(block)=V_(wed g e)`
`2-mu+3=(1)/(2)1(6)^(2)-(1)/(2)3v^(2)`
`mu=(54)/(80)=0.675`