A college student lifts a box of books with a mass of 20kg and gives it to her father to carry down the hall. It takes the student 3 seconds to lift the box to waist height of 1m and the trip down the 25m hall takes 5 minutes. Assume that while the box is being lifted its velocity is constant.
(1) How much work does the student do in order to lift the box?
The force on the box due to gravity is
Since the box is not accelerating in the y direction, the net force must equal 0 and the student must exert a force of 196N away from the ground. This force is exerted in the same direction as the direction of motion, so f is 0 and cosf = 1. The work equation therefore reduces to
