brake

A brake is a mechanical device used in a system to inhibit motion by absorbing energy, most commonly through friction. It converts the kinetic energy of a moving object (like a vehicle, wheel, or axle) into heat energy, which is then dissipated into the atmosphere. Brakes are a critical safety and control component in numerous applications.

Function and Design
The primary functions of a braking system are to:
Stop or decelerate a moving system quickly and efficiently.
Hold a system stationary when parked (e.g., parking brakes on a slope).
Ensure safety by allowing operators to control speed and movement in normal and emergency situations.
Brakes are typically classified based on their power source and the mechanism used for the final friction contact.
Types of Brakes
By Frictional Contact Mechanism
Disc Brakes: The most common type in modern vehicles, especially the front wheels. A caliper assembly forces brake pads (friction material) against both sides of a rotating disc (rotor) attached to the wheel, generating friction to slow or stop rotation. They offer superior heat dissipation, reducing a condition called "brake fade".
Drum Brakes: Found on older vehicles and the rear wheels of some low-cost modern cars. Inside a rotating drum, curved brake shoes are forced outward to press against the inner surface of the drum to create friction and slow the wheel. They are generally cheaper but less efficient at dissipating heat than disc brakes.
By Power Source
Hydraulic Brakes: The most common system in passenger cars, working on Pascal's principle. When the pedal is pressed, fluid pressure is transmitted through lines to activate the brake mechanisms at the wheels.
Pneumatic (Air) Brakes: Primarily used in heavy commercial vehicles like buses and trucks where significant braking force is required. They use compressed air pressure, generated by a compressor, to apply the brakes.
Mechanical Brakes: Use rods, levers, and cables to transfer force from the operator to the brake components. This system is often used for parking/handbrakes and in older vehicles.
Electromagnetic Brakes: Used in trains, hybrid, and electric vehicles. They use magnetic fields to generate resistance and achieve frictionless braking, which increases reliability and longevity.
Common Applications
Brakes are essential for safety and control across diverse industries:
Automotive: Service brakes (foot pedal) and parking brakes (hand/emergency brake) are critical for vehicle safety and operation.
Industrial Machinery: Used in manufacturing lines, conveyor systems, hoists, cranes, and presses to control motion and ensure safety stops.
Aerospace: Employed in aircraft landing gear and also as air brakes (flaps) to reduce speed in flight.
Rail Transit: Trains use powerful braking systems, often electromagnetic or air brakes, for primary stopping functions.