# FHSST Physics/Pressure/Summary

Pressure The Free High School Science Texts: A Textbook for High School Students Studying Physics Main Page - << Previous Chapter (Newtonian Gravitation) - Next Chapter (Heat and Properties of Matter) >> Important Equations and Quantities

# Important Equations and Quantities

 Units Quantity Symbol Unit S.I. Units Direction Pressure P pascal (Pa) $Kg{m^{-1}}{s^{-2}}$ No1

## Non Si Units for pressure

PSI: PSI stands for pounds per square inch. One PSI is equal to 6,894.76 Pascals

Atm: Atm stands for Atmosphere. This is the atmospheric pressure at sea level. I atm is equal to 101,325 Pascals

Hydrostatic pressure is the pressure due to the weight of a fluid.

$p = \rho g h\,$

where:

   ρ (rho) is the density of the fluid (i.e., the practical density of fresh water is 1000 kg/m3);
g is the acceleration due to gravity (approximately 9.81 m/s2 on earth's surface);
h is the height of the fluid column (in metres). Other units can be used if the rest of the units used in the equation are defined in a consistent way.


It is important to realize that air is a fluid. This equation can be used to find the pressure created by air. This also means that if we are trying to find the pressure of a liquid open to the atmosphere, we must add in the atmospheric pressure to the pressure of the liquid to find the total pressure.

## Notes

### 1

Pressure is force divided by area, so in a sense it does have a direction as force has a direction. The term pseudovector is sometimes used for such quantities.