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

A piston with small cross section area A₁, exerts a force F₁ on the surface of a liquid such as oil. The applied pressure P = F₁ / A₁ is transmitted through 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 multiplication factor equal to the ratio of the areas of the two pistons. dentist’s chairs, car lifts and jacks, any elevators and hydraulic brakes all use pascal’s law principle.