A 350 piano slides 3.8 down a 31 incline and is kept from accelerating by a man who is pushing back on it parallel to the incline (see the figure ).

A 350 piano slides 3.8 down a 31 incline and is kept from accelerating by a man who is pushing back on it parallel to the incline (see the figure ). The effective coefficient of kinetic friction is 0.40.