A 400 kg piano slides 4.0 m down a 30 degree incline and is kept from accelerating by a man who is pushing back on it parallel to the incline.
A. Determine the force exerted by the man.
B. Determine the work done by the man on the piano.
C. Determine the work done by the force of gravity.
D. Determine the net work done on the piano. Ignore friction.