A mass of 3kg rests on a rough plane inclined at 60 degrees to the horizontal. The coefficient of friction is 1/5. Find the force P acting parallel to the plane applied to the mass, in order to just prevent motion down the plane.

Firstly draw a diagram of the problem.Then resolve the forces into their components parallel and perpendicular to the plane.Resolving parallel: P + Fmax = 3gsin(60) equation 1.Resolving perpendicular: R = 3gcos(60) =14.7N equation 2. Then substitute Fmax= Mu.R into equation 1 and then sub R (equation 2) into equation 1. Then solve to find P. P = 3gsin(60)- Mu.R P = 3gsin(60) - 0.2x14.7= 22.5 N