Simple machine

In physics, a simple machine is any device that only requires the application of a single force to work.

The traditional list of simple machines is:

• The inclined plane
• The screw
• The wedge
• The lever
• The wheel
• The pulley

Some say there are only five, with the wedge being a moving inclined plane.

All of these convert low forces into high forces or vice versa, and the ratio of the input force to the output force is the mechanical advantage. Mechanical advantage for a lever is equal to the ratio of the length of its two arms, for example, and the mechanical advantage for an inclined plane with the force acting parallel to the plane is the cosecant of the angle of inclination. The mechanical advantage of a simple machine is also affected by factors such as friction and elasticity, however, and so will usually differ somewhat from its theoretical value.

These simple machines fall into two general classes; those dependent on the vector resolution of forces (inclined plane, wedge, screw, toggle joint) and those in which there is an equilibrium of torques (lever, pulley, wheel). 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.

See also:

• Invention

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There was also a record label named Simple Machines: http://www.simplemachines.net which closed as of April 1998.