Hydrostatic Pressure

At a point,

Pascal’s law

The hydrostatic pressure at a point is the same from all directions. Applies only for hydrostatic pressure.

Proof

Consider the fluid element shown, containing the point .

From the image:

For equilibrium:

As all approaches : . Therefore

Variation along directions

Proof

Let be the pressure at the point .

By considering equilibrium of this fluid element containing .

In the direction,

Similarly can be proven.

In the direction,

For incompressible fluids

is constant. .

Isobar

Surface of constant pressure.

Types of pressure

Atmospheric Pressure

Pressure exerted by atmospheric air.

Gauge Pressure

Measured in respect to atmospheric pressure.

Absolute Pressure

Measured in respect to perfect vaccum.

Piezometric pressure

Pressure diagram

A diagram showing the variation of pressure along a submerged surface.

Pressure Head

Height of a particular fluid column that will produce the pressure at a point.

Pressure difference between 2 points