a thin rod, of length L = 0.80 m and negligible mass that can pivot about one end to rotate in a vertical circle. A heavy ball of mass m = 9.0 kg is attached to the other end. The rod is pulled aside through an angle ? = 36.0° and released.
a. As the ball descends to its lowest point, how much work does its weight do on it?
b. As the ball descends to its lowest point, what is the change in the gravitational potential energy of the ball-Earth system?
c. If the gravitational potential energy is taken to be zero at the lowest point, what is its value just as the ball is released?