Section: Mechanical Comprehension

28) Which mechanical components are typically used between a wheel and an axle to reduce friction?

1. springs
2. hinges
3. bearings
4. levers

A set of bearings is typically a set of small metal balls packed in a groove and lubricated with grease or oil. The wheel rubs against one side of each ball, and the axle rubs against the other side. The net effect is that the wheel rolls much more easily.