a bat hitting a baseball a paper clip attracted to a magnet a refrigerator pushed across the floor a bicycle tire rubbing against the road
I gave my students this multiple choice question: Which of these is an example of a non-contact force acting on an object?

Only one answer is correct among these 4 choices:
- a bat hitting a baseball
- a paper clip attracted to a magnet
- a refrigerator pushed across the floor
- a bicycle tire rubbing against the road

Could you tell me which one is correct?

a paper clip attracted to a magnet