Changes

[[File:lighterstill.jpg]][[File:Gears_animation.gif|right|frame]]

[[File:lighterstill.jpg]][[File:GearsGIF.gif‎|right|frame]]

==Origin==

==Origin==

[http://nordan.daynal.org/wiki/index.php?title=English#ca._1100-1500_.09THE_MIDDLE_ENGLISH_PERIOD Middle English] ''gere'', from Old Norse ''gervi'', ''gǫrvi''; akin to [http://nordan.daynal.org/wiki/index.php?title=English#ca._600-1100.09THE_OLD_ENGLISH.2C_OR_ANGLO-SAXON_PERIOD Old English] ''gearwe'' equipment, clothing, ''gearu'' ready  

[https://nordan.daynal.org/wiki/index.php?title=English#ca._1100-1500_.09THE_MIDDLE_ENGLISH_PERIOD Middle English] ''gere'', from Old Norse ''gervi'', ''gǫrvi''; akin to [https://nordan.daynal.org/wiki/index.php?title=English#ca._600-1100.09THE_OLD_ENGLISH.2C_OR_ANGLO-SAXON_PERIOD Old English] ''gearwe'' equipment, clothing, ''gearu'' ready  

*[http://en.wikipedia.org/wiki/14th_century 14th Century]

*[https://en.wikipedia.org/wiki/14th_century 14th Century]

==Definitions==

==Definitions==

*1a : [[clothing]], garments

*1a : [[clothing]], garments

:b : one of two or more [[adjustments]] of a transmission (as of a bicycle or motor vehicle) that determine [[mechanical]] [[advantage]], relative [[speed]], and direction of travel  

:b : one of two or more [[adjustments]] of a transmission (as of a bicycle or motor vehicle) that determine [[mechanical]] [[advantage]], relative [[speed]], and direction of travel  

==Description==

==Description==

A '''gear''' is a rotating [[machine]] part having cut teeth, or ''cogs'', which mesh with another toothed part in order to [[transmit]] [http://en.wikipedia.org/wiki/Torque torque]. Two or more gears working in tandem are called a [http://en.wikipedia.org/wiki/Transmission_(mechanics) transmission] and can produce a mechanical advantage through a [http://en.wikipedia.org/wiki/Gear_ratio gear ratio] and thus may be considered a simple [[machine]]. Geared devices can [[change]] the [[speed]], torque, and [[direction]] of a [[power]] source. The most common situation is for a gear to mesh with another gear; however, a gear can also mesh with a non-rotating toothed part, called a rack, thereby producing [http://en.wikipedia.org/wiki/Translation_(physics) translation] instead of rotation.

A '''gear''' is a rotating [[machine]] part having cut teeth, or ''cogs'', which mesh with another toothed part in order to [[transmit]] [https://en.wikipedia.org/wiki/Torque torque]. Two or more gears working in tandem are called a [https://en.wikipedia.org/wiki/Transmission_(mechanics) transmission] and can produce a mechanical advantage through a [https://en.wikipedia.org/wiki/Gear_ratio gear ratio] and thus may be considered a simple [[machine]]. Geared devices can [[change]] the [[speed]], torque, and [[direction]] of a [[power]] source. The most common situation is for a gear to mesh with another gear; however, a gear can also mesh with a non-rotating toothed part, called a rack, thereby producing [https://en.wikipedia.org/wiki/Translation_(physics) translation] instead of rotation.

The gears in a transmission are analogous to the wheels in a [http://en.wikipedia.org/wiki/Pulley pulley]. An advantage of gears is that the teeth of a gear prevent slipping.

The gears in a transmission are analogous to the wheels in a [https://en.wikipedia.org/wiki/Pulley pulley]. An advantage of gears is that the teeth of a gear prevent slipping.

When two gears of unequal number of teeth are combined, a mechanical advantage is produced, with both the [http://en.wikipedia.org/wiki/Rotational_speed rotational speeds] and the torques of the two gears differing in a simple [[relationship]].

When two gears of unequal number of teeth are combined, a mechanical advantage is produced, with both the [https://en.wikipedia.org/wiki/Rotational_speed rotational speeds] and the torques of the two gears differing in a simple [[relationship]].

In transmissions which offer multiple gear ratios, such as bicycles and cars, the term gear, as in first gear, refers to a [http://en.wikipedia.org/wiki/Gear_ratio gear ratio] rather than an actual physical gear. The term is used to describe similar devices even when the gear ratio is continuous rather than discrete, or when the device does not actually contain any gears, as in a [http://en.wikipedia.org/wiki/Continuously_variable_transmission continuously variable transmission].

In transmissions which offer multiple gear ratios, such as bicycles and cars, the term gear, as in first gear, refers to a [https://en.wikipedia.org/wiki/Gear_ratio gear ratio] rather than an actual physical gear. The term is used to describe similar devices even when the gear ratio is continuous rather than discrete, or when the device does not actually contain any gears, as in a [https://en.wikipedia.org/wiki/Continuously_variable_transmission continuously variable transmission].

The earliest known reference to gears was circa A.D. 50 by [http://en.wikipedia.org/wiki/Hero_of_Alexandria Hero of Alexandria], but they can be traced back to the Greek mechanics of the [http://en.wikipedia.org/wiki/Alexandrian_school Alexandrian school] in the 3rd century B.C. and were greatly developed by the Greek polymath [http://en.wikipedia.org/wiki/Archimedes Archimedes] (287–212 B.C.).[3] The [http://en.wikipedia.org/wiki/Antikythera_mechanism Antikythera mechanism] is an example of a very early and intricate geared device, designed to calculate astronomical positions. Its time of construction is now estimated between 150 and 100 BC.[http://en.wikipedia.org/wiki/Gears]

The earliest known reference to gears was circa A.D. 50 by [https://en.wikipedia.org/wiki/Hero_of_Alexandria Hero of Alexandria], but they can be traced back to the Greek mechanics of the [https://en.wikipedia.org/wiki/Alexandrian_school Alexandrian school] in the 3rd century B.C. and were greatly developed by the Greek polymath [https://en.wikipedia.org/wiki/Archimedes Archimedes] (287–212 B.C.).[3] The [https://en.wikipedia.org/wiki/Antikythera_mechanism Antikythera mechanism] is an example of a very early and intricate geared device, designed to calculate astronomical positions. Its time of construction is now estimated between 150 and 100 BC.[https://en.wikipedia.org/wiki/Gears]

[[Category: Physics]]

[[Category: Physics]]