Physics: How Pascal's Law Multiplies Hydraulic Force

Pascal's principle states that pressure applied to a confined, incompressible liquid is transmitted equally and undiminished in all directions throughout the liquid. This idea underpins hydraulic systems, where a small input force on a narrow piston generates a much larger output force on a wider one — the basis of car brakes, lifts and industrial presses. The key relationship is pressure: P = F/A. Because the pressure is the same at both pistons, the ratio of force to area is equal on each side, so F₁/A₁ = F₂/A₂. A small force over a small area therefore produces a proportionally larger force over a larger area, giving hydraulic systems their mechanical advantage. In practice, friction between piston seals and cylinder walls converts some input energy into heat, so real output forces fall below theoretical predictions.