What is the difference between hydrostatic pressure and atmospheric pressure?

1 Answer
Aug 15, 2014

Here's my explanation.


Both water and air and water are fluids — they can flow from one place to another.

The difference is that water is an incompressible fluid — its density is almost constant as the pressure changes — while air is a compressible fluid — its density changes with pressure.

Hydrostatic pressure is the pressure exerted by an incompressible fluid (a liquid) at a given point, due to the weight of the fluid above it.


Atmospheric pressure is the pressure exerted on a surface by the weight of the atmosphere (a compressible fluid) above it.


The atmospheric pressure at the surface of the earth is approximately 1 bar.

A mercury barometer works because the hydrostatic pressure of the mercury column balances the atmospheric pressure exerted on the surface of the mercury.

Mercury barometer
(From imgarcade.com)