Pressure is the force exerted on or against an object or surface (by something in contact with it) per unit area over which the force is spread. The definition of physical force is important in order to understand pressure, as they are related. Force is an interaction, which if unresisted, will change the movement of an object and also might cause the said object to accelerate, slow down, remain its position or reshape/deform. Force can also be defined as a push or pull. The standard unit of force is Newton.
Pressure variations depend on the amount of applied force and on the size of the area it is applied over. The universal symbol for pressure is p or P. The common units of measure for pressure are Pascal, newton per square meter, pound per square inch, bar, atmosphere.
There are several types of pressure such as Absolute pressure, Atmospheric pressure, Differential pressure, Gauge pressure, Hydrostatic pressure, Vapor pressure.
| Atmospheres | Bars | Inches of Mercury | Millibars | Pascals | Pounds per Square Inch | Torrs | |
|---|---|---|---|---|---|---|---|
| 1 Atmosphere = | 1 | 1.0133 | 29.9213 | 1013 | 101325 | 14.6959 | 760 |
| 1 Bar = | 0.9869 | 1 | 29.53 | 1000 | 100000 | 14.5038 | 750.0617 |
| 1 Inch of Mercury = | 0.0334 | 0.0339 | 1 | 33.8639 | 3386 | 0.4912 | 25.4 |
| 1 Millibar = | 0.00098692 | 0.001 | 0.0295 | 1 | 100 | 0.0145 | 0.7501 |
| 1 Pascal = | 9.8692 x 10-6 | 1 x 10-5 | 0.0002953 | 0.01 | 1 | 0.00014504 | 0.007501 |
| 1 Pound per Square Inch = | 0.068 | 0.0689 | 2.036 | 68.9476 | 6895 | 1 | 51.7149 |
| 1 Torr = | 0.001316 | 0.001333 | 0.0394 | 1.3332 | 133.3224 | 0.0193 | 1 |
