A man wants to slide down a block of mass `m` which is kept on a fixed inclined plane of inclination `30^(@)` as shown in the figure .Initially the block is not sliding .
To just start sliding the man pushed the block down the inclined with a force `F`. Now , the block starts accelerating. To move it downwards with conatant speed the man starts pulling the block with same force. Surface are such that ratio of maximum static friction to kinetic friction is `2` Now, answer the following questions.

What minimum force is required to move it up the incline with constant speed?

Options

A. `(2)/(3) mg`
B. `(mg)/(2)`
C. `(7 mg)/(6)`
D. `(5 mg)/(6)`

Answer

D

Explanation

`F'' = mg sin theta + mu_(k) mg cos theta`
`= (mg)/(2) + ((2)/(3 sqrt(3))) mg ((sqrt3)/(2))`
`= (5 mg)/(6)`