a book sitting on a shelf a ball rolling down a hill a runner about to start a race a window getting hot from the sun
I gave my students this multiple choice question: Which is an example of kinetic energy?

Only one answer is correct among these 4 choices:
- a book sitting on a shelf
- a ball rolling down a hill
- a runner about to start a race
- a window getting hot from the sun

Could you tell me which one is correct?

a ball rolling down a hill