Topic summary
Hydraulic brakes

Extracted from the Wikipedia article Hydraulic brake.
An example of a hydraulic brake system
Hydraulic brakes transfer energy to stop an object, normally a rotating axle. In a very simple brake system, with just two cylinders and a disc brake, the cylinders could be connected via tubes, with a piston inside the cylinders. The cylinders and tubes are filled with an incompressible liquid. The two cylinders have the same volume, but different diameters, and thus different cross-section areas. The cylinder that the operator uses is called the master cylinder. The spinning disc brake will be adjacent to the piston with the larger cross-section. Suppose the diameter of the master cylinder is half the diameter of the slave cylinder, so the master cylinder has a cross-section four times smaller. Now, if the piston in the master cylinder is pushed down 40 mm, the slave piston will move 10 mm. If 10 newtons (N) of force are applied to the master piston, the slave piston will press with a force of 40 N.