Hydraulic Jacks

Definition

A hydraulic jack is a jack (a device used to lift heavy loads, like wheels of vehicles) that uses hydraulic power.

How they work

A hydraulic jack works on pascal's principle,i.e, when force is applied to an enclosed fluid, it moves in all directions undiminished. 

Let me explain this a little clearer with an example. Let's say we have two syringes (without the needle, of course) named A & B. Let's fill A with water. If we push the piston of A, the water will flow through the tube & go into B, hence pushing B's piston upwards. 

If something is placed on top of B's piston then it will be moved.

Hydraulic jacks work the same way.

So, the next you see someone on the road lifting their tires with a jack, you can walk up to them & tell them how their jack works ;-)   

Citations

https://www.thomasnet.com/articles/materials-handling/how-hydraulic-jacks-work