Friction both ways

A cycle needs its brakes to grip. It needs its chain to move easily.

The rule

We need friction to grip, walk, write and stop. To grip is to hold without slipping. We reduce friction where it wastes effort or wears parts. Wear is the slow rubbing away of a surface.

Oil, and smooth shapes, reduce friction. Oil makes a thin layer between the surfaces. So they rub less.

Try the lab to finish this lesson.