Units of Measurement/Pressure
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Pressure is the force per unit area applied in the direction perpendicular to a surface. Mathematically, pressure is defined as
where:
- P is pressure
- F is the component of force perpendicular to the surface
- A is the area of the surface
When a force is constant over an area, the pressure acting on that area is simply
It can be given the units of N.m^{-2}. Pressure is a scalar quantity, thus it acts in all directions at any given point. In order for pressure to create a force, the pressure must be integrated over some area.
pascal | bar | standard atmosphere | torr | pound per square inch | |
---|---|---|---|---|---|
Pa | bar | atm | Torr | psi | |
1 Pa | ≡ 1 N/m^{2} | 10^{−5} | 9.8692×10^{−6} | 7.5006×10^{−3} | 145.04×10^{−6} |
1 bar | 10^{5} | ≡ 10^{5} Pa | 0.98692 | 750.06 | 14.5037744 |
1 at | 0.980665 ×10^{5} | 0.980665 | 0.96784 | 735.56 | 14.223 |
1 atm | 1.01325 ×10^{5} | 1.01325 | ≡ p_{0} | 760 | 14.696 |
1 Torr | 133.322 | 1.3332×10^{−3} | 1.3158×10^{−3} | ≈ 1 mm_{Hg} | 19.337×10^{−3} |
1 psi | 6.895×10^{3} | 68.948×10^{−3} | 68.046×10^{−3} | 51.715 | ≡ 1 lbf/in^{2} |