We use the wheel and axle in gears. Gears have teeth around the outer rim.When the teeth of two gears fit together and one gear turns, it will cause the other gear to turn, but in the opposite direction. When the gear are the same size and they have the same number of teeth, they both turn at the same speed. If one gear is larger than the other, however, the smaller gear will turn faster. We use gears to regulate speed and direction of motion in complex machines and to increase/decrease the force applied