A 10.0 kg box is placed on a ramp that is inclined at 30.0 degrees to the horizontal.

Determine the force of friction required to keep the block stationary.
Determine the minimum coefficient of friction required to keep the box stationary.

1 answer

force down ramp = m g sin 30
= .5 m g

normal force = m g cos 30
maximum friction force = mu m g cos 30

slides if:
.5 m g > mu m g cos 30
so
mu >/= .5/cos 30 = .58