1. What is the gravitational energy (relative to the unstretched surface of the trampoline) of the 20 kg ball at its apex 2 m above the trampoline?

E= mgh = 20(10)(2) =400 J Therefore, the gravitational energy is 400 J.

2. What is the kinetic energy of the ball just before impacting the trampoline?

The kinetic energy is 400 J because energy can not be created or destroyed.

3. At maximum stretch at the bottom of the motion, what is the sum of the elastic and gravitational energy of the ball?

use g= 10 N/kg