Pascal

From Free net encyclopedia

The pascal (symbol: Pa) is the SI unit of pressure. It is equivalent to one newton per square meter, and was used in SI under that name before the name pascal was adopted by the 14th CGPM in 1971. The same unit is also used for stress, Young's modulus, and tensile strength.

1 Definition
2 SI multiples
3 Origin
4 Explanation
5 Comparison to other units of pressure
6 See also

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Definition

1 pascal (Pa) = 1 N/m² = 1 J/m³ = 1 kg·m^–1·s^–2

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SI multiples

Template:SI multiples

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Origin

The unit is named after Blaise Pascal, the eminent French mathematician, physicist, and philosopher.

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Explanation

1 megapascal (MPa) = 1 000 000 Pa = 1 N/mm².

Standard atmospheric pressure is 101 325 Pa = 101.325 kPa = 1013.25 hPa = 1013.25 mbar = 760 Torr. This definition is used for pneumatic fluid power (ISO R554), and in the aerospace (ISO 2533) and petroleum (ISO 5024) industries.

In 1985, IUPAC recommended that standard atmospheric pressure should be 100 000 Pa = 1 bar = 750 Torr. The same definition is used in the compressor and the pneumatic tool industries (ISO 2787). [1]

Meteorologists worldwide have for a long time measured atmospheric pressure in millibars. After the introduction of SI units, many preferred to preserve the customary pressure figures. Therefore, meteorologists use hectopascals today for air pressure, which are equivalent to millibars, while similar pressures are given in kilopascals in practically all other fields, where the hecto prefix is hardly ever used.

1 hectopascal (hPa) = 100 Pa = 1 mbar.

1 kilopascal (kPa) = 1000 Pa = 10 hPa.

In the former Soviet mts system, the unit of pressure is the pieze, which is equivalent to one kilopascal.

The Unicode computer character set has dedicated symbols ㎩ (Template:U) for Pa and ㎪ (Template:U) for kPa, but these exist merely for backward-compatibility with some older ideographic character-sets and are therefore deprecated.

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