Brake 65423 223875269 2008-07-06T08:05:23Z DineshAdv 5929255 /* See also */ {{otheruses1|the vehicle component}} [[Image:Disc_brake.jpg|right|240px|thumbnail|[[Disc brake]] on a [[motorcycle]].]] A '''brake''' is a device for slowing or stopping the motion of a [[machine]] or [[vehicle]], or alternatively a device to restrain it from starting to move again. The [[kinetic energy]] lost by the moving part is usually translated to [[heat]] by [[friction]]. Alternatively, in [[regenerative braking]], much of the energy is recovered and stored in a [[flywheel]], [[capacitor]] or turned into [[alternating current]] by an [[alternator]], then [[Rectifiers|rectified]] and stored in a [[battery (electricity)|battery]] for later use. Note that kinetic energy increases with the square of the velocity ('''''E'' = 1/2·''m''·''v''<sup>2</sup>''' relationship). This means that if the [[speed]] of a vehicle doubles, it has four times as much energy. The brakes must therefore dissipate four times as much energy to stop it and consequently the [[braking distance]] is four times as long. Brakes of some description are fitted to most [[wheel]]ed [[vehicle]]s, including [[automobile]]s of all kinds, [[truck]]s, [[train]]s, [[motorcycle]]s, and [[bicycle]]s. [[Baggage cart]]s and [[shopping cart]]s may have them for use on a [[moving ramp]]. Some [[Fixed-wing aircraft|aeroplane]]s are fitted with wheel brakes on the [[undercarriage]]. Some aircraft also feature [[Air brake (aircraft)|air brakes]] designed to slow them down in flight. Notable examples include [[glider]]s and some [[World War II|WWII]]-era [[fighter aircraft]]. These allow the aircraft to maintain a safe speed in a steep descent. The [[Saab 17|Saab B 17]] [[dive bomber]] used the deployed undercarriage as an air brake. [[Deceleration]] and avoiding [[acceleration]] when going downhill can also be achieved by using a low [[gear]]; see [[engine braking]]. [[Vehicle brake#Friction brake|Friction brakes]] on cars store the heat in the rotating part ([[drum brake]] or [[disc brake]]) during the brake application and release it to the air gradually. ==Effects on noise pollution== [[Image:Aa horsehearsebrake 00.jpg|thumb|right|Brake lever on a horse-drawn [[hearse]]]] {{main|Roadway noise}} The action of braking for motor vehicles produces recognizable sound level emissions, varying with the specific tire types and with the roadway surface type produces considerable effect upon sound levels or [[noise pollution]] emanating from moving vehicles.<ref>[http://www.springerlink.com/content/x1707075n815g604/ C.Michael Hogan, '' Analysis of highway noise'', Journal of Water, Air, & Soil Pollution, Volume 2, Number 3, Biomedical and Life Sciences and Earth and Environmental Science Issue, Pages 387-392, September, 1973, Springer Verlag, Netherlands ISSN 0049-6979]</ref> There is a considerable range in acoustical intensities produced depending upon the specific tire tread design and the rapidity of deceleration required to slow the vehicle. ==See also== {{col-begin}} {{col-2}} * Archaic past tense of break (see [[wiktionary:brake|brake]]) * [[Air brake (aircraft)]] * [[Air brake (rail)]] * [[Air brake (road vehicle)]] * [[Bicycle brake systems]] * [[Brake-by-wire]] (or [[electromechanical]] braking) * [[Line lock]] * [[Brake lining]] * [[Brake pad]] * [[Brake shoe]] * [[Bundy tube]] * [[Disc brake]] * [[Drum brake]] {{col-2}} * [[Electromagnetic brake]] * [[Electronic Parking Brake]] * [[Engine braking]] * [[Hand brake]] * [[Hydraulic brake]] * [[Jake brake]] also known as J braking * [[Overrun brake]] * [[Parking brake]] * [[Railway brake]] * [[Regenerative braking]] * [[Threshold braking]] * [[Trail braking]] * [[Vehicle brake]] {{col-end}} ==References== {{reflist}} ==External links== {{Wiktionary}} *[http://www.carbibles.com/brake_bible.html The Brake Bible] *[http://auto.howstuffworks.com/brake.htm How Stuff Works - Brakes] *[http://www.autocarrepair.net/Brake-System-Repairs.html High Quality Brake System Repairs Guide] *[http://ebc-brakes.activebrakesdirect.com/ Brakes News Blog] *[http://www.black-ridge.com/brakes-general.htm How to know when to replace your brakes] *[http://www.opencortex.org/cn00000233 Resource on Stanfords solar car brakes] [[Category:Auto parts]] [[Category:Brakes]] [[Category:Vehicle braking technologies]] [[bg:Спирачка]] [[cs:Brzda]] [[de:Bremse]] [[et:Pidur]] [[es:Freno]] [[eo:Bremsilo]] [[fa:ترمز]] [[fr:Frein]] [[gd:Breig (càr)]] [[hr:Kočnice]] [[id:Rem]] [[it:Freno]] [[he:בלם (מכשיר)]] [[hu:Fék]] [[nl:Rem]] [[ja:ブレーキ]] [[pl:Hamulec]] [[pt:Travão]] [[ru:Тормоз]] [[simple:Brake]] [[fi:Jarru]] [[sv:Broms]] [[tg:Тормоз]] [[tr:Fren]]