Wedge

A wedge is a simple machine used to split, cut, or hold things in place. It is shaped like a triangle, with a thin edge on one end and a thick end on the other. When you push on the thick end, the wedge turns that push into a strong sideways force along its slanted sides. This force is what splits wood, cuts through food, or lifts a heavy object a tiny bit off the ground.

A wedge is really two inclined planes joined back to back. The longer and thinner the wedge, the less force you need to use. A short, fat wedge takes more muscle but splits things faster.

Wedges are everywhere once you start looking. The blade of an axe is a wedge. So is a knife, a chisel, a nail, and the front teeth in your mouth. Even a doorstop is a wedge, holding a door open by jamming itself into the small space near the floor.

People have used wedges for a very long time. Stone wedges chipped into sharp edges are some of the oldest tools ever found, going back more than two million years, long before modern humans existed. Early people used them to cut meat, shape wood, and crack bones. Every time you bite into an apple, you are using six of the oldest tools in the world: your front teeth.