Equilibrium of body on the rough inclined plane:
If the inclination is less than angle of friction, the body remains in equilibrium without any external force. If body is to be moved upwards or downwards in this condition an external force is needed. But if the inclination of plane is more than the angle of friction, body will not remain in equilibrium. The body will move upward and downward external force will be needed to keep the body in equilibrium.
This type of problems is solved by resolving the forces along the plane and perpendicular to planes. The force of friction (F), which is always equal to µ.R, is acting in opposite direction of motion of the body