Which principle states that in a closed system, fluid pressure is constant at every point?

The principle that states fluid pressure is constant at every point in a closed system is known as Pascal's principle. This principle, formulated by Blaise Pascal in the 17th century, indicates that when pressure is applied to a confined fluid, the change in pressure is transmitted undiminished throughout the fluid.

This means that if there is an increase in pressure at any point within a closed fluid system, that increase will be felt equally at all other points in the system, leading to uniform pressure distribution. This principle is fundamental in understanding how hydraulic systems work, such as in hydraulic brakes or lifts, where the force applied at one point can be transmitted to another point with the same intensity.

In contrast, Bernoulli's principle describes the relationship between pressure, velocity, and height in fluid flow, particularly emphasizing the conservation of energy along a streamline. Archimedes’ principle deals with buoyancy and how objects behave in fluids, and the hydrostatic principle relates to the pressure exerted by a fluid at rest due to the weight of the fluid above it. Thus, while each of these principles is significant in fluid dynamics, it is Pascal's principle that specifically addresses the constancy of fluid pressure in a closed system.