Q: What is the term for force that opposes motion between any touching surfaces?


Read this paragraph and choose the correct option from the provided answers:

All machines make work easier, but they don’t increase the amount of work that is done. You can never get more work out of a machine than you put into it. In fact, a machine always does less work on an object than the user does on the machine. That’s because a machine must use some of the work put into it to overcome friction. Friction is the force that opposes motion between any surfaces that are touching. All machines involve motion, so they all have friction. How much work is needed to overcome friction in a machine depends on the machine’s efficiency.

 Choices:

- gravity

- stress

- tension

- friction


A:
friction