We can use hydraulics to transfer forces from one machine to another. Liquid hydraulics work because you can’t push a liquid together or make it occupy a smaller space than it already does.

This is essentially Pascal’s law

Pressure exerted on a in-compressible fluid, in a confined space is transmitted equally in all directions throughout the fluid

Hydraulics

To the right is a basic animation of how breaks work in a car.

The break fluid (oil) is forced out and applies hydraulic pressure, causing the break pads to clamp on the disc break. This results in Friction, causing the wheel to stop turning.

But how do hydraulics work.

Observe the animation to the left.

Here we have two pistons of equal size and volume. The fluid is forced out of one piston (effort piston) and transferred to the other (load piston). When the effort piston is pushed, it creates pressure. If the pressure is enough the load piston will move.

In this case, since both pistons are the same size and the volume of liquid is kept constant, the amount lifted is the same as the force applied.

If we can’t use hydraulics as a force multiplier then they aren't much good to us. So how can we increase the amount of force lifted, while keeping the applied force low?

We can spread the force from one piston evenly across two other pistons.

Notice as we push out 4 ml of liquid, each piston fills with 2 ml equally.

In order to understand how hydraulics amplify force, you need to know some basic equations.

Click here for more information on hydraulic multiplication