7.3-kg box is being lifted by means of a light rope that is threaded through a single, light, frictionless pulley that is attached to the ceiling.
a) If the box is being lifted at a constant speed of 2.0 m/s, what is the power delivered by the person pulling on the rope?
b) If the box is lifted, at constant acceleration, from rest on the floor to a height of 1.5 m above the floor in 0.42 s, what average power is delivered by the person pulling on the rope?