Roll one ball toward another, and see what happens when they collide. Place a glass of water in the freezer, and see how long the water takes to become solid. Compress a spring by different amounts, and see how far it can launch a ball into the air. Roll a ball from the top of an inclined plane and determine the amount of time it takes to get to the bottom.
I gave my students this multiple choice question: Which investigation might be used to demonstrate potential energy?

Only one answer is correct among these 4 choices:
- Roll one ball toward another, and see what happens when they collide.
- Place a glass of water in the freezer, and see how long the water takes to become solid.
- Compress a spring by different amounts, and see how far it can launch a ball into the air.
- Roll a ball from the top of an inclined plane and determine the amount of time it takes to get to the bottom.

Could you tell me which one is correct?

Compress a spring by different amounts, and see how far it can launch a ball into the air.