What is Pascal's principle?

Pascal's principle: P = F ÷ A. Push on a liquid that is shut in and the extra pressure spreads equally through all of it, pressing on every wall. So a small push on a small piston becomes a big push on a big piston, which is how brakes, jacks and lifts multiply force.

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Chapters in this interactive model

1. Squeeze a liquid and the push goes everywhere: Pascal’s principle: pressure in a trapped fluid spreads equally to every part of it.
2. A light push, a mighty squeeze: Hydraulic brakes and the car jack turn a small force into a huge one.
3. Height is pressure: tanks, taps and spray arms: A rooftop tank pushes water down to every tap, and a pump pushes it out of every nozzle.
4. Your blood pressure and your popping ears: A cuff squeezes an artery through your arm; air pushes on both sides of your eardrum.
5. Bursting barrels and spongy brakes: A thin tube of water can split a barrel, a bubble of air can ruin a brake, and nothing is free.