- #1

bigsmile

- 6

- 0

1) Just before the ball hits the bottom, the sum of its kinetic and potential energy is:

**Zero J**

2) After the ball comes to a stop in the mud, the sum of its potential and kinetic energy is:

**-196 J**

On #1, why is "sum of kinetic and potential energy" turns to zero? I just guess it is due to conservation of energy, but I don't know how to use Math to prove it.

I know in theory Sum of all work equals the change of KE. I am not sure how to apply here. Before the ball hits the bottom, it should still have velocity and KE >0,

In addition, I really don't understand why the answer in both #1 and #2 are different. I thought the answer to #2 is also zero too due to conservation of energy. Why is the sum equal to a) a negative 196 instead of +196 and b) final potential energy of -196 J?

I am very confused. Please help.