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cal conditions and laws which you must know and consider when you make pressure
measurements.
3.
The Nature of Fluid Pressure and Its Transmission. In order to understand the
nature of pressure in a fluid, you must recall and understand Pascal's law
(principle) which concerns fluid pressure.
We are referring to the law which
states: "Pressure applied to an inclosed fluid is transmitted equally in all
directions without loss and acts with equal force on equal surfaces."
From this
law we can reason that the pressure existing in the fluid in an inclosed system
exerts a force at right angles against the walls surrounding the fluid, is shown in
Figure 1.
Figure 1.
Fluid pressure within a system
a. The shape of a fire hose before the application of pressure from the fire
hydrant is illustrated in Figure 1, A.
Figure 1, B, shows how equal forces are
applied in all directions on equal surfaces of the walls surrounding the water.
Figure 2 supports that portion of Pascal's law (principle) which concerns the
ability of a fluid to transmit pressure without a loss. The 5 lbs/in2 output of
the grease gun in Figure 2 depends on the seal made between the moving gasket and
the inner walls of the gun. It is obvious that the area of the piston surface is
four or five times that of the pimp opening. However, since the pressure exerted
by the piston is 5 pounds for each in2 of surface, the pressure exerted at the 1
in2 pump opening is 5 pounds.
Figure 2.
A fluid transmits pressure without a loss
b. Hydraulic (Hydrostatic) Press Operating Principle. Let's examine Pascal's
principle as it is applied to the hydraulic (hydrostatic) press in Figure 3.
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