Question

If µs = 0.40 and m g = 20 N , what minimum force F will keep the box from falling?

Answer 1

`50 N`

Explanation:

Here, frictional force acting upwards is `mu*N`

which will prevent the block from falling if its magnitude will be equal to its weight i.e `mg`

so, `mu N = mg`

or, `N=50`

now,from the free body diagram drawn,force (`F`) required to do such will be equals to the normal reaction(`N`) provided by the wall on the block.

so,`F= 50 N`