Hydraulic Lift: Principle and Working

Class 11: Mechanical Properties of Fluid 

Hydraulic lift:
A hydraulic lift is a device for moving objects using force created by pressure on a liquid inside a cylinder that moves a piston upward.

Principle:

If pressure is applied at any point of incompressible liquid then the same pressure is transmitted to all the points and on the walls of the container.

Working:

Hydraulic lift consists of two cylinders  and  of different cross-sectional areas connected with a pipe. The cylinders are filled with incompressible liquid and frictionless pistons are fitted in both the cylinders as shown in figure.

 : Cross sectional Area of cylinder 

 : Cross sectional Area of cylinder 

 : force applied on the smaller piston

 : Pressure exerted on smaller piston

 : Resulting Force on bigger piston

 : Pressure transmitted to bigger piston

As we know: 

According to Pascal Law:

As we know that  

This shows that when we apply a force at the smaller piston, a greater force will act on the bigger piston. So, we can lift a heavier object by applying a lower force.