Hydraulic systems use liquids to transmit pressure throughout a system. Liquids are incompressible, so applying force to a confined liquid creates equal pressure everywhere in the liquid. This allows a small force applied to a small piston to create a larger force on a larger piston. Car braking systems use this principle by applying pressure through brake fluid to stop the vehicle, transmitting a small force on the brake pedal into the larger force needed to stop the wheels.

1. Hydraulic systems work by using liquids under pressure. Make use of two properties of liquids: Liquids are incompressible If pressure is applied to a trapped liquid, the pressure is transmitted to all parts of the liquid .

2. A small force applied to the smaller piston can lift a greater load on the larger piston.

3. Force of 70 N applied to smaller piston of 0.001m 2 . Pressure = Force / Area = 70 / 0.001 = 70 000 Pa

4. Pressure is transmitted in the liquid and is the same everywhere within the liquid. Thus pressure under the bigger piston must also be 70000 Pa. Bigger piston has area of 0.1 m 2 , hence load Force = Pressure x Area = 70000 x 0.1 = 7000 N

5. Braking system of car Car brakes use the transmission of liquid pressure to stop a car. Driver applies a relatively small push on the brake pedal, pedal moves a rod connected to a piston. This piston slides inside a master cylinder and presses on the fluid inside. The high pressure fluid moves out of the cylinder into the pipes or brake lines.

6. Using principle that pressure is transmitted equally in all directions at the same time, the brake pistons of the wheel experience the same pressure. The area of the piston at the brake pedal is much smaller than the total area of the brake piston. Thus a small force applied on the brake pedal is enough to stop a fast moving car which requires a large braking force.