Pascal (unit)
| pascal | |
|---|---|
?u=http://en.wikipedia.org/wiki/File:Psidial.jpg) A pressure gauge reading in psi (red scale) and kPa (black scale) | |
| General information | |
| Unit system | SI |
| Unit of | pressure or stress |
| Symbol | Pa |
| Named after | Blaise Pascal |
| Conversions | |
| 1 Pa in ... | ... is equal to ... |
| SI base units: | kg⋅m−1⋅s−2 |
| US customary units: | 1.45038×10−4 psi |
| atmosphere: | 9.86923×10−6 atm |
| bar: | 10−5 bar |
| barye (CGS unit) | 10 Ba |
The pascal (symbol: Pa) is the unit of pressure in the International System of Units (SI). It is also used to quantify internal pressure, stress, Young's modulus, and ultimate tensile strength. The unit, named after Blaise Pascal, is an SI coherent derived unit defined as one newton per square metre (N/m2).[1] It is also equivalent to 10 barye (10 Ba) in the CGS system. Common multiple units of the pascal are the hectopascal (1 hPa = 100 Pa), which is equal to one millibar, and the kilopascal (1 kPa = 1000 Pa), which is equal to one centibar.
The unit of measurement called standard atmosphere (atm) is defined as 101,325 Pa.[2] Meteorological observations typically report atmospheric pressure in hectopascals per the recommendation of the World Meteorological Organization, thus a standard atmosphere (atm) or typical sea-level air pressure is about 1013 hPa. Reports in the United States typically use inches of mercury[3] or millibars (hectopascals).[4][5] In Canada these reports are given in kilopascals.[6]
Etymology
[edit]The unit is named after Blaise Pascal, noted for his contributions to hydrodynamics and hydrostatics, and experiments with a barometer. The name pascal was adopted for the SI unit newton per square metre (N/m2) by the 14th General Conference on Weights and Measures in 1971.[7][8]
Definition
[edit]The pascal can be expressed using SI derived units, or alternatively solely SI base units, as:
where N is the newton, m is the metre, kg is the kilogram, s is the second, and J is the joule.[9]
One pascal is the pressure exerted by a force of magnitude one newton perpendicularly upon an area of one square metre.
Standard units
[edit]The unit of measurement called an atmosphere or a standard atmosphere (atm) is 101325 Pa (101.325 kPa).[10] This value is often used as a reference pressure and specified as such in some national and international standards, such as the International Organization for Standardization's ISO 2787 (pneumatic tools and compressors), ISO 2533 (aerospace) and ISO 5024 (petroleum). In contrast, International Union of Pure and Applied Chemistry (IUPAC) recommends the use of 100 kPa as a standard pressure when reporting the properties of substances.[11]
Unicode has dedicated code-points
