It's perhaps the second week of your introductory physics course. Your instructor starts talking about friction and writes the following two formulas on the board. Then there is probably some sort of ...

Friction is the force between two surfaces that are sliding, or trying to slide, across each other. For example, when you try to push a book along the floor, friction makes this difficult. Friction ...

This acts when an object is at rest and prevents it from starting to move. It increases up to a certain limit as you apply an external force to initiate motion. This acts when an object is already in ...