Pascal's law
Pressure change in a confined fluid is transmitted equally everywhere.
Pascal's law, also known as Pascal's principle or the principle of transmission of fluid-pressure, is a fundamental concept in fluid mechanics. It states that a pressure change at any point in a confined incompressible fluid is transmitted equally and undiminished throughout the fluid.
- field
- Fluid mechanics
- nationality
- French
- known_for
- Pascal's law (principle of transmission of fluid-pressure)
Lore & Background
Pascal's principle is defined as a change in pressure at any point in an enclosed incompressible fluid at rest being transmitted equally and undiminished to all points in all directions throughout the fluid, with the force due to the pressure acting at right angles to the enclosing walls. For a fluid column in uniform gravity, this principle can be stated mathematically as Δp = ρg·Δh, where the change in pressure between two elevations is due to the weight of the fluid between them. The variation with height does not depend on any additional pressures, so any change in pressure applied at any point is transmitted undiminished throughout the fluid.
Reader's Guide
Pascal's law is the basis for force amplification in hydraulic systems, such as the hydraulic press and automobile lift. In a U-tube with pistons, pressure exerted on one piston is transmitted equally to the other; if the second piston has a larger area, the output force is multiplied proportionally. For example, if the area ratio is 50:1, a 1 N input force produces a 50 N output force. This does not violate energy conservation because the distance moved by the larger piston is reduced by the same factor. The principle applies to both liquids and gases, as seen in service station lifts where compressed air transmits pressure through oil to lift a vehicle. The experiment known as Pascal's barrel, involving a long tube causing a barrel to burst, is mentioned nowhere in Pascal's preserved works and may be apocryphal, attributed to him by 19th-century French authors.
Did You Know?
- The formula Δp = ρg·Δh is a specific case of the Navier–Stokes equations without inertia and viscosity terms.
- In a hydraulic press, a 1 N input force can produce a 50 N output force if the larger piston has 50 times the area of the smaller one.
- The experiment known as Pascal's barrel is mentioned nowhere in Pascal's preserved works and may be apocryphal.
Frequently Asked Questions
Who is Pascal's law?
Pascal's law is a foundational principle in fluid mechanics, named after the French mathematician Blaise Pascal. It describes how pressure behaves inside a sealed, incompressible fluid.
What are Pascal's law's powers?
It dictates that any pressure change applied at one point in a confined fluid gets passed along equally and without loss to every other point in that fluid. This is the mechanism behind hydraulic presses and vehicle brakes.
How does Pascal's law's story end?
The principle has no narrative arc, but its practical 'ending' is the design of hydraulic systems where a small force on a small piston produces a proportionally larger force on a bigger piston. Engineers rely on this outcome daily in machinery and transport.
Why is Pascal's law important?
It provides the theoretical backbone for all hydraulic technology, from car brakes to industrial presses. Without the equal-transmission rule, fluid-based force amplification simply would not work.
What field does Pascal's law belong to?
It lives squarely in fluid mechanics, a branch of classical mechanics. Though Pascal was French and worked in the 17th century, the principle remains a core topic in any introductory fluid-dynamics course.
More in Classical And Fluid Mechanics 1-19
Spotted an error? Know more?
This is a living reference — every entry is fact-audited, and reader corrections feed straight into our audit queue. Suggest an edit · See this site's audit record