Pressure and Force Definition

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Pressure and Force Definition
The foundation of modern hydraulic powered systems was established when a scientist named Blaise Pascal discovered that pressure in a fluid acts equally in all directions. This concept is known as Pascal's Law. The application of Pascal's Law requires the understanding of the relationship between force and pressure.

Force may be defined as a push or pull exerted against the total area of a surface. It is expressed in pounds. Pressure is the amount of force on a unit area of the surface. That is, pressure is the force acting upon one square inch of a surface.
The relationship between pressure and force is expressed mathematically.
F=P x A

F = force in lbf
P = pressure in lbf/in2., (psi)
A = area in in2.

In a hydraulic system, the oil pressure at the inlet to the cylinder is 1500 psi, and the area of the piston over which the oil pressure acts is two square inches. Calculate the force exerted on the piston.

Since F = P x A, the force of the oil on the piston is calculated as follows.
F = 1500 lbf/in2.x 2 in2.
= 3000 lbf