How do gears provide a mechanical advantage?

A.T.

As Drakkith said, gears are basically levers that can operate continuously. See:
http://en.wikipedia.org/wiki/Lever

They allow you to trade distance for force, or the other way around. For example this simple gear outputs less force, but more velocity than goes in:

Here the lever mechanism is indicated as a red line:

A.T.	As Drakkith said, gears are basically levers that can operate continuously. See: http://en.wikipedia.org/wiki/Lever They allow you to trade distance for force, or the other way around. For example this simple gear outputs less force, but more velocity than goes in: Here the lever mechanism is indicated as a red line: