Pressure

Pressure
Pressure exerted by particle collisions inside a closed container. The collisions that exert the pressure are highlighted in red.
Common symbols
p, P
SI unitpascal (Pa)
In SI base unitskgm−1s−2
Derivations from
other quantities
p = F / A
Dimension

Pressure (symbol: p or P) is the force applied perpendicular to the surface of an object per unit area over which that force is distributed.[1]: 445  Gauge pressure (also spelled gage pressure)[a] is the pressure relative to the ambient pressure.

Various units are used to express pressure. Some of these derive from a unit of force divided by a unit of area; the SI unit of pressure, the pascal (Pa), for example, is one newton per square metre (N/m2); similarly, the pound-force per square inch (psi, symbol lbf/in2) is the traditional unit of pressure in the imperial and US customary systems. Pressure may also be expressed in terms of standard atmospheric pressure; the unit atmosphere (atm) is equal to this pressure, and the torr is defined as 1760 of this. Manometric units such as the centimetre of water, millimetre of mercury, and inch of mercury are used to express pressures in terms of the height of column of a particular fluid in a manometer.

  1. ^ Knight, Randall D. (2007). "Fluid Mechanics". Physics for Scientists and Engineers: A Strategic Approach (google books) (2nd ed.). San Francisco: Pearson Addison Wesley. p. 1183. ISBN 978-0-321-51671-8. Retrieved 6 April 2020. Pressure itself is not a Force, even though we sometimes talk "informally" about the "force exerted by the pressure. The correct statement is that the Fluid exerts a force on a surface. In addition, Pressure is a scalar, not a vector.


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