brake

Two common braking systems: the disc brake (left) and the drum brake (right). In the disc brake, increased hydraulic pressure of the brake fluid in the pistons forces the brake pads against the steel disc attached to the wheel. A self-adjusting mechanism balances the force on each pad. In the drum brake, increased pressure of the brake fluid within the slave cylinder forces the brake pad against the brake drum attached to the wheel.

How disc brakes on a car work. A small braking force is applied to the brake pedal. This creates pressure on the brake fluid in the master cylinder, which is transmitted through the fluid to the slave cylinders. The slave cylinder pistons press the brake pads against the brake discs to slow the wheels. The mechanical advantage derives from the piston in the master cylinder having a narrow bore and moving a greater distance, while the slave cylinder has a larger bore and moves just a few millimetres.

Device used to slow down or stop the movement of a moving body or vehicle. The mechanically applied calliper brake used on bicycles uses a scissor action to press hard rubber blocks against the wheel rim. The main braking system of a car works hydraulically: when the driver depresses the brake pedal, liquid pressure forces pistons to apply brakes on each wheel.

Two types of car brakes are used. Disc brakes are used on the front wheels of some cars and on all wheels of sports and performance cars, since they are the more efficient and less prone to fading (losing their braking power) when they get hot. Braking pressure forces brake pads against both sides of a steel disc that rotates with the wheel. Drum brakes are fitted on the rear wheels of some cars and on all wheels of some passenger cars. Braking pressure forces brake shoes to expand outwards into contact with a drum rotating with the wheels. The brake pads and shoes have a tough friction lining that grips well and withstands wear.

Many trucks and trains have air brakes, which work by compressed air. On landing, jet planes reverse the thrust of their engines to reduce their speed quickly. Space vehicles use retrorockets for braking in space and use the air resistance, or drag of the atmosphere, to slow down when they return to Earth.