Pascal's law

Beginner

Pressure change transmits equally through a confined fluid.

A pressure change applied to an enclosed fluid is transmitted undiminished to every part of it and to the walls. It underlies hydraulic systems.

Worked example

Pressing a brake pedal pushes fluid to all four brakes.

Common mistake

Only for incompressible fluids at rest.

In more detail

Pascal's law states that pressure applied to an enclosed fluid is transmitted undiminished to every part of the fluid and the container walls.

Hydraulic brakes in cars transmit pedal pressure to the wheels.
Car lifts use Pascal's law to raise heavy vehicles.
A car's hydraulic brakes transmit the pressure from the pedal equally to each wheel's brake cylinder.

Does Pascal's law create energy?

No. The force is multiplied, but the distance moved is increased in the same ratio.

Where does it apply?

To fluids that are enclosed and at rest, or in hydraulic systems.

Why does the pressure spread equally?

The fluid transmits pressure in all directions, so any change at one point is felt everywhere in the confined fluid.