| 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.
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