A brake is a device for slowing or stopping the motion of a machine, and to keep it from starting to move.
The kinetic energy lost by the moving part is usually translated to heat by friction. Alternatively, in regenerative braking, the energy is recovered and stored in a flywheel, capacitor or other device for later use.
The kinetic energy increases with the square of the velocity (E = ½m•v2 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 longer.
Friction brakes on cars store the heat in the rotating part (drum or disc) during the brake application and release it to the air gradually.
Brakes of some description are fitted to most wheeed vehicles, including automobiles of all kinds, trucks, trains, motorcycles, and bicycles. Baggage and shopping carts may have them for use on a moving ramp. Some aeroplanes are fitted with wheel brakes on the undercarriage. Some aircraft also feature air brakes designed to slow them down in flight. Notable examples include gliders and some World War II-era fighter aircraft which allow the aircraft to maintain a safe speed in a steep descent. Most modern cars have vacuum assisted servo brakes.
Deceleration and avoiding acceleration when going downhill, is also achieved by using a low gear, see engine braking.
Types of brake
- Air brake (aircraft)
- Disk brake
- Drum brake
- Electromagnetic brake
- Engine braking
- Hydraulic brake
- Regenerative brake
- Vacuum brake
- Template:US patent Wagon brake. Issued September 29, 1836. ...a new and useful improvement in the use and application of brakes to the wheels of wagons, stagecoaches, and other vehicles...
- Template:US patent Disc brake. Issued December 29, 1925.
- Template:US patent Anti-lock brake. Issued December 13, 1960.
- Template:US patent Devices for controlling carbon disc brakes, more particularly for aircraft. Issued April 6, 1976.
- emergency brake
- engine braking
- threshold braking
- trail braking
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