# Wikijunior:How Things Work/Inclined Plane

An inclined plane is any sloped surface, like a slide or a ramp. The inclined plane is one of the six simple machines. It is a flat surface whose ends are at different heights. An inclined plane is a machine that does not always move.

## Who invented it?

Inclined planes occur in nature, so in that sense no one created them, they only needed to be noticed. For example, mountains form inclined planes and animals use them for climbing. They will often choose paths that are not as steep, but longer to save effort (power).

Stairways are a kind of inclined plane. One of the earliest known stairways was built as part of a wall surrounding Tel e-Sultan in the present-day city of Jericho. These stairs were built around 8,000 BC. In Egypt about 2,500 BC, it is believed that people made earth ramps as a way to move heavy stones for the Pyramids

## How does it work?

An inclined plane makes it easier to raise something heavy, like a rock. Instead of lifting the rock straight up, you can raise it from its original location with less force by pushing it up a ramp. But there are some considerations that need to be taken, the distance the object must travel is always increased (not a straight vertical) and some of the energy is expended in the attrition with the surface. In a steep ramp, it will be harder to push the rock but you won't need to push it as far. If you push it up a ramp that is not as steep, it will have to be longer. Because work is force multiplied by distance, the amount of work remains mostly the same, In a steep ramp, it will be harder to push the rock/load but you won't need to push it as far. There maybe economical benefits in using a smaller force and having more time, as the load can easily be made to stay at rest as it travels the inclined plane, something that will be harder or even impractical in a straight vertical lift.

## How dangerous is it?

Like all the other simple machines that multiply force, it can be dangerous. If you go down a slide too fast you could lose control and hurt yourself. Avalanches and mud slides are examples of natural disasters that are dangerous because of the power of an inclined plane. If you go down a really steep inclined plane you could get hurt.

## How does it vary?

There are many devices based on the principles of the inclined plane.

Ramps and slides are one common example of the inclined plane. Ramps enable accessing heights that would be too difficult to scale vertically. Chutes and slides allow people and things to be safely lowered from a height. Eliminating friction from a slide increases the maximum speed at which an object can move down the slide. Because of this, slides are one of the most common and popular forms of entertainment and are common on playgrounds all over the world. In the sport skiing, participants accelerate to extremely high speeds utilizing only the inclined plane of a mountain slope provided by nature.

The roof of a house is usually an inclined plane. The incline allows it to shed water and snow.

Water wheels use inclined planes mounted around a rotating wheel to gain energy from moving water. They transform the force of the water into torque that turns a shaft. Similarly, sails extract the momentum of moving air to drive a vehicle, and windmills catch the wind in order to move a set of sails around a shaft to perform work.

Aircraft wings provide lift by redirecting momentum generated from lateral movement. Air flows faster over the top of the wing than it flows over the bottom. Propellers are inclined planes that transmits power by converting rotational motion into thrust.

Two of the other six simple machines are based on the inclined plane. The wedge is a compound portable inclined plane. It is made of two inclined planes that meet at an edge. The screw is an inclined plane wrapped around a cylinder.

## How has it changed the world?

It has changed the world by making heavy things easier to lift up, so people could use less power and energy.

## What idea(s) and/or inventions had to be developed before it could be created?

The inclined plane is such a simple machine, nothing had to be invented before it. It does run parallel with the basic notions about gravity, momentum, forces and energy.