FHSST Physics/Pressure/Summary

From Wikibooks, open books for an open world
< FHSST Physics‎ | Pressure
Jump to: navigation, search
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) >>
Pressure
Important Equations and Quantities

Important Equations and Quantities[edit]

Table 10.1: Units used in Pressure
Units
Quantity Symbol Unit S.I. Units Direction
Pressure P pascal (Pa) Kg{m^{-1}}{s^{-2}} No1



Non Si Units for pressure[edit]

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 (head pressure)[edit]

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[edit]

1[edit]

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.