GEAR BASICS CLOZE
distance final gear input invented larger many properly simple together wheel
To understand the
you first have to understand the lever. The lever and fulcrum make up a
machine where a stiff beam (the lever) rotates about a fixed pivot (the fulcrum).
The principle of the lever has been used since before written language. Levers were initially
so that heavy stone blocks could be moved using only muscle power. Levers still form the operating principle behind
common machines, both powered and hand operated. A practical lever includes the lever itself and the fulcrum. To work
, the fulcrum is usually fixed in place relative to the lever.
Like other simple machines, the lever is best understood through the concepts of
and output forces. The output force can be
or smaller than the input force, depending on the length of the lever and where you place the fulcrum.
A gear is a modification of the
and axle. It just has teeth around it. Like all simple machines, gears may change the direction in which a force is applied; or increase or reduce a force or the
over which a force is applied.
Gears work in teams. Two gears working
is called a gear train. The gear on the train to which the force is first applied is called the driver. The
gear on the train to which the force is first applied is called the driven gear. Any gears between the driver and the driven gears are called the idlers.
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The Science of Gears