Pascal's Law
Pascal's Law states that pressure applied to a confined, incompressible fluid is transmitted equally, undiminished, in every direction throughout that fluid. It is the entire physical basis of hydraulic machinery.
01Definition
Pascal's Law states that pressure applied to a confined, incompressible fluid is transmitted equally, undiminished, in every direction throughout that fluid. It is the entire physical basis of hydraulic machinery.
02Physical Principle
Because pressure is force divided by area, the same pressure acting on a large piston produces far more force than it does acting on a small one. Push a small piston with a modest force and connect it through oil to a much larger piston, and the large piston pushes back with a proportionally larger force — trading distance for force exactly the way a lever does, except the 'lever arm' here is a ratio of areas, and the force can be redirected anywhere a hose can reach.
03Mathematical Foundation
04Interactive Diagram — Hydraulic Force Multiplier
Set the input piston force and the ratio between the two piston areas to see how much force the output piston delivers.
Pressure is transmitted equally throughout the fluid — only the piston areas differ.
05Interesting Facts
- A car's hydraulic brakes are a direct, everyday application of the same law that lets a 40-tonne excavator curl its bucket: a small pedal piston, a much larger caliper piston.
- Hydraulic fluid is treated as incompressible for these calculations — it isn't perfectly so, but the compression is small enough at working pressures to ignore for engineering purposes.
- Because pressure, not force, is what's constant throughout the system, the same hydraulic pump can drive a small, fast cylinder and a huge, slow one simultaneously, just by giving them different piston areas.