Definition
A principle of fluid mechanics stating that pressure applied to a confined, incompressible fluid is transmitted equally and undiminished in all directions throughout the fluid, and acts at right angles to the surfaces of its container.
Plain English
If you push on a liquid that is sealed inside a container, that push spreads evenly through the whole liquid, and pushes outward against every wall with the same strength.
Context Anchor
Seen in aircraft hydraulic system discussions, especially brakes, landing gear, and other systems that use fluid pressure to move or hold parts.
Derivation
Named after Blaise Pascal, the 17th-century French scientist who first described the behavior of pressure in confined fluids. Knowing the name is tied to a person — not a technical word — helps the student stop trying to decode it and just accept it as a label.
Why Pilots Care
Aircraft hydraulic systems depend on this law to multiply force from cockpit controls to brakes, landing gear, and flight surfaces.
Analogy
Imagine a sealed balloon full of water. Squeeze it anywhere and the whole surface bulges outward at once — the pressure didn’t just go where you pushed, it went everywhere equally.
Grounding Statement
In a closed hydraulic line, a push at one end can create a useful push at another end because the liquid carries the pressure through the system.
Intuition Check
Pascal’s Law is not about liquid flowing faster or farther. It is about pressure being carried evenly through a trapped liquid.
Example Sentence 1
Aircraft hydraulic brake systems rely on Pascal’s Law to multiply the small force from the pilot’s foot into a much larger braking force at the wheels.
Example Sentence 2
Understanding Pascal’s Law helps confirm why a small pump input can lift heavy landing gear through the hydraulic lines.