Question

A ball falls to the ground as shown below. A* Potential energy = 120J Kinetic energy =0 B* Kinetic energy = 50J C* Potential Energy = 0 1) What is the KE of ball when it hits the ground? 2) what is PE of the ball at B? 3) Which law have you made in answering this question?

Answer 1

1) By conservation of total mechanical energy:

total energy at A= total energy at C
(PE + KE) at A= (PE + KE) at C
120+0 =K.E +0
so K.E = 120J

2)...
(PE + KE) at A= (PE + KE) at B
120+0 = PE + 50
so PE = 70 J

3) We got the answer by applying law of conservation of total mechanical energy.