Editing Pendulum (section)

{{Short description|Mechanism for regulating the speed of clocks}}
{{About|the weight suspended from a pivot|other uses}}
[[File:Simple gravity pendulum.svg|thumb|300px|"Simple gravity pendulum" model assumes no friction or air resistance.]]

A '''pendulum''' is a device made of a [[weight (object)|weight]] suspended from a [[wikt:pivot|pivot]] so that it can swing freely.<ref>{{cite encyclopedia
 | title = Pendulum
 | encyclopedia = Miriam Webster's Collegiate Encyclopedia
 | pages = 1241
 | publisher = Miriam Webster
 | year = 2000
 | isbn = 978-0-87779-017-4
}}</ref> When a pendulum is displaced sideways from its resting, [[Mechanical equilibrium|equilibrium position]], it is subject to a [[restoring force]] due to [[gravity]] that will accelerate it back toward the equilibrium position. When released, the restoring force acting on the pendulum's mass causes it to [[oscillate]] about the equilibrium position, swinging back and forth. The time for one complete cycle, a left swing and a right swing, is called the [[Frequency|period]]. The period depends on the length of the pendulum and also to a slight degree on the [[amplitude]], the width of the pendulum's swing.

The regular motion of pendulums was used for timekeeping and was the world's most accurate timekeeping technology until the 1930s.<ref name="Marrison">{{cite journal
 | last=Marrison | first=Warren
 | title=The Evolution of the Quartz Crystal Clock
 | journal=Bell System Technical Journal
 | year=1948| volume=27 | issue=3 | pages=510–588
 | url=http://www.ieee-uffc.org/main/history.asp?file=marrison
 | doi=10.1002/j.1538-7305.1948.tb01343.x
 | url-status=dead
 | archive-url=https://web.archive.org/web/20110717061023/http://www.ieee-uffc.org/main/history.asp?file=marrison
 | archive-date=2011-07-17
| url-access=subscription
 }}</ref> The [[pendulum clock]] invented by [[Christiaan Huygens]] in 1656 became the world's standard timekeeper, used in homes and offices for 270 years, and achieved accuracy of about one second per year before it was superseded as a time standard by the [[quartz clock]] in the 1930s.  Pendulums are also used in [[scientific instrument]]s such as [[accelerometer]]s and [[seismometer]]s. Historically they were used as [[gravimeter]]s to measure the [[Gravity of Earth|acceleration of gravity]] in geo-physical surveys, and even as a standard of length. The word ''pendulum'' is [[Neo-Latin]], from the Latin {{lang|la|pendulus}}, meaning {{gloss|hanging}}.<ref>{{cite book
 | last = Morris | first = William, Ed.
 | title = The American Heritage Dictionary, New College Ed
 | publisher = Houghton-Mifflin
 | year = 1979
 | location = New York
 | page = [https://archive.org/details/americanheritag00morr/page/969 969]
 | url = https://archive.org/details/americanheritag00morr/page/969
 | isbn = 978-0-395-20360-6
}}</ref>