Which principle of pressure states that pressure on water is always perpendicular?

Pascal's principle, also known as Pascal's law, asserts that when pressure is applied to a confined fluid at rest, that pressure is transmitted equally in all directions and acts perpendicular to the surface in contact with the fluid. This principle is fundamental in understanding how fluids behave under pressure, particularly in applications involving hydraulics.

In the context of water and other fluids, this means that at any point in a confined fluid, the pressure exerted on the fluid will always be directed perpendicular to the surfaces of the container or any objects submerged within it. This characteristic allows for effective pressure transfer in hydraulic systems, such as those found in fire apparatus and industrial machinery, where maximizing force distribution is crucial for functionality.

While other principles, like the hydraulic principle and Bernoulli’s principle, deal with the movement and energy dynamics of fluids, they do not specifically address the directional nature of pressure in relation to contact surfaces as Pascal's principle does.