R= mg cos a + Psin a Note: If the surface is smooth, then F=0
Examples
. A body of mass 5 kg rests on an inclined
plane whose angle of inclination to the
horizontal can be varied. If the coefficient of
friction between the body and the surface of
the inclined plane is 0.3, at what angle does
the body start to slide down from the plane?
Solution
RR
D