Imagine you need to load a heavy box into a truck. Lifting it straight up is really hard. But if you slide it up a long slanted board, the job gets much easier. That slanted board is a simple machine called an inclined plane, or a ramp.

An inclined plane is just a flat surface with one end higher than the other. Instead of lifting a load straight up, you push it up the gentle slope. The ramp holds up part of the load's weight for you, so your push does not have to.

Using a ramp means you push with less force, but you have to push for a longer distance. You trade a short, hard lift for a long, easy push. The load ends up just as high, but your arms are much happier.

The gentler the slope, the easier the push. A long ramp that rises slowly is easier to climb than a short, steep one. That is why wheelchair ramps zigzag back and forth instead of going straight up.

Ramps are everywhere once you start looking. Slides at the park, roads that wind up a hill, and the sloped board that helps a truck get loaded are all inclined planes. Even a staircase is a ramp cut into steps.

Long ago, builders used giant ramps to raise the heavy stones of pyramids and castles. Without engines or cranes, a simple slope let many workers push a huge block up to the top.