Principle of Operation of a Hydraulic Jack:

A hydraulic jack is used to lift heavy vehicles (like cars, trucks, buses etc.) to required heights in automobile workshops so that mechanic can do work conveniently under the vehicles. A force F₁ is applied at the piston of smaller area of cross-section A₁ (Figure). This pressure is transmitted to a piston of larger cross-sectional area (that is, the platform which lifts the vehicle) A₂. Now,

Figure: A Schematic Diagram Showing the Principle of Operation of a Hydraulic Jack

according to Pascal's law, the pressure would remain the same in the larger piston. But, due to larger area of cross-section of this piston, the force F₂ exerted by it will be larger. That is, if pressure keep the similar, force will be proportional to the area of cross-section of the pistons as per the relation, F = PA. However, you must note that the work done on the smaller piston will be the same as the work done by the larger piston; F₁ d₁ = F₂ d₂ where d₁ and d₂ are the displacements of the smaller and larger pistons respectively such that d₁ > d₂.