Two syringes and a tube can lift a car. Discover how liquids and gases transfer force, and how cylinder size trades force for distance.
Take two syringes of the same size, connect them with a tube, and fill the system with a fluid. Pushing the plunger of one syringe (the "driver" or "master") forces the fluid through the tube and pushes out the plunger of the other syringe (the "driven" or "slave"). This is the simplest possible way to transfer force from one place to another without any direct mechanical link.
Pascal's principle states that pressure exerted on one part of an enclosed fluid is transferred equally, without loss, in all directions to every other part of the system. This is the reason hydraulic systems work reliably: whatever pressure you apply at the driver piston is felt equally throughout the fluid and acts on every surface it touches, including the driven piston.
If the two syringes (cylinders) are the same size, pushing one plunger in by a certain distance pushes the other plunger out by the same distance, with the same force — nothing is gained or lost. But if the cylinders are different sizes, something interesting happens: because the same volume of liquid moves through both cylinders, a small cylinder must move a lot further than a large cylinder to shift the same volume.
A hydraulic press uses a small-diameter input piston and a large-diameter output piston to multiply force, allowing a modest push to generate an enormous squeezing force — used to crush cars, press metal panels, or compact waste. A hydraulic jack works the same way: repeatedly pumping a small lever piston pushes small amounts of oil into a much larger piston under the car, gradually lifting a heavy load with modest hand force. A one-way valve lets more oil in on every pump stroke while stopping it flowing back, so the load stays lifted between strokes.
A systems diagram describes how a device works by showing INPUT (what goes in — e.g. a person pumping a lever), PROCESS (what happens inside — e.g. oil is pushed from a small cylinder into a large cylinder through a one-way valve) and OUTPUT (the result — e.g. a heavy load is raised). Drawing a hydraulic jack as a systems diagram helps you explain the process clearly without needing full engineering drawings.
Once a solution (like a hydraulic jack) has been designed or chosen, it should be evaluated against a standard set of questions:
Set the diameter of the input (driver) and output (driven) pistons to see the force multiplication ratio and how far each piston moves.