Pascal’s Law

Pascal’s law states that

“Pressure applied to an enclosed fluid is transmitted undiminished to every portion of the fluid and the walls of the containing vessel”.

A small force (F₁) is applied to a piston with a small area (A₁), resulting a much larger force F₂ on the larger piston. It is schematically illustrated in the figure. A well-known application of Pascal’s law is the hydraulic lift, which is used to support or lift heavy objects.

A piston with a small cross-sectional area A₁, exerts a force F₁ on the surface of a liquid such as oil. The applied pressure P = F₁ / A₁ is transmitted through the connecting pipe to a larger piston of area A₂.

The applied pressure is the same in both cylinders, so

Where, P = pressure (Pa or N/m²)
F = force (N)
A = area (m²)

In the above figure A₂ > A₁, therefore, F₂ > F₁.

Thus, hydraulic life is a force multiplying device with a multiplication factor equal to the ratio of the areas of the two pistons. Dentists' chairs, car lifts and jacks, any elevators, and hydraulic brakes all utilize Pascal’s Law principle.