Gears

Gears are one way to transfer motion from one place to another. They work together in groups of two or more. One gear turns another, which may turn another, and so on... Gears are measured by counting the number of teeth they have. When used with an axle, gears are an example of the simple machine called the "wheel and axle". Gears can mesh together in many different ways to transfer motion. Gears can increase or decrease force, torque or speed or change direction.

For more information on gears from www.howstuffworks.com: Click Here