|A simple machine is any device that only requires the application of a single force to work. Simple machines all convert a smaller amount of force exerted over a larger distance to a greater amount of force exerted over a shorter distance, or vice versa.
The ratio of the output force to the input force is the called mechanical advantage. The mechanical advantage of a lever is equal to the ratio of its two arms. For example, the mechanical advantage of an inclined plane (with the force acting parallel to the plane) is the cosecant of the angle of inclination.
- Note: Real machines are also affected by factors such as friction and elasticity, so the actual mechanical advantage of a simple machine will usually differ from its theoretical value.
Simple machines are often used in combination as components of more complex machines; for example the Archimedes screw, which is a pump, is an example of a complex machine where the screw is a helical inclined plane.