What is Pascal's Law??
Consider the equilibrium of a small fluidelement in the form of a triangular prism asshown in figure, surrounding a point in thefluid.
A relationship can be established betweenthe pressures px in the x-direction, py in they-direction and ps normal to any planeinclined at any angle 𝜗 to the horizontal atthis point.
Therefore, indicates that the pressure at a point is the same in all directions. This is known as
Pascal’s law and applies to a fluid at rest.
If the fluid is flowing, shear stresses will be set up as a result of relative motion between the particles of
the fluid. The pressure at a point is then considered to be the mean of the normal forces per unit area
(stresses) on three mutually perpendicular planes. Since these normal stresses are usually large compared
with shear stresses it is generally assumed that Pascal’s law still applies.