A block of mass m slides down an inclined plane of inclination ? with uniform speed. The coefficient of friction between the block and the plane is µ . Find the contact force between the block and the plane.

The normal reaction for the block on the plane is mgcos? .

The contact force between them is the friction(f)=µmgcos?

µmgcos? .

If the speed is to be constant then there shouldn't be no accelaration..The condition is tan(angle of inclination of the inclined plane)=coefficient of friction.

since the block is moving with constant velocity that means net force acting on the body is 0..

friction force(f) = mgsin@       ...............1

           f = u(normal reaction)

            f =uN

        mgsin@ = uN

          N = mgsin@/u    (contact force)