A sufficiently long plane of mass `4kg` is placed on a smooth horizontal surfaces A small block of mass `2kg` is placed over the plank and is beging acted upon by a time verying horizontal force `F = (0.5t)` where F is in newton and t is in second as shown in figure. The coefficient of friction slipping the plank and the block is given is `mu_(s) = mu_(k) = mu` time `t = 12s` the relative slipping between the plank and the block is just likely to accor

The coefficient of friction `mu` is equal to

Options

A. `0.10`
B. `0.15`
C. `0.20`
D. `0.30`

Answer

c

Explanation

`0.5t = mu mg (1+ (m)/(M)), t = 12 s`
`rArr mu = 0.2`