gravity acting on the wagon friction acting on the wagon the mass of the wagon the mass of the child
I gave my students this multiple choice question: A child rides a wagon down a hill. Eventually, the wagon comes to a stop. Which is most responsible for causing the wagon to stop?

Only one answer is correct among these 4 choices:
- gravity acting on the wagon
- friction acting on the wagon
- the mass of the wagon
- the mass of the child

Could you tell me which one is correct?

friction acting on the wagon