Pascal (pressure)

Pascal (pressure)

The pascal (symbol: Pa) is the SI derived unit of pressure, stress, Young's modulus and tensile strength. It is a measure of perpendicular force per unit area i.e. equivalent to one newton per square meter or one joule per cubic metre. In everyday life, the pascal is perhaps best known from meteorological barometric pressure reports, where it occurs in the form of hectopascals(1 hPa = 100 Pa). [ [http://www.ofcm.gov/fmh-1/fmh1.htm U.S. Federal Meteorological Handbook] ] . In other contexts, the kilopascal is more commonly used, for example on bicycle tire labels. [ISO 5775: Bicycle tires and rims] One hectopascal corresponds to about 0.1% and one kilopascal to about 1% of atmospheric pressure (near sea level): one hectopascal is thus equivalent to a millibar; one atmosphere is equal to 1013.25 hPa.

Definition

:1 pascal (Pa) ≡ 1 N/m2 ≡ 1 J/m3 ≡ 1 kg/(m·s2)

Origin

The unit is named after Blaise Pascal, the eminent French mathematician, physicist, and philosopher noted for his experiments with a barometer, an instrument to measure air pressure.The name "pascal" was adopted for the SI unit newton per square metre by the 14th CGPM in 1971. [http://www.bipm.fr/en/convention/cgpm/14/pascal-siemens.html]

Miscellaneous

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 harmonized to 100,000 Pa = 1 bar = 750 Torr. The same definition is used in the compressor and the pneumatic tool industries (ISO 2787). [cite web| url=http://www.compressor.co.za/news/may%20news.htm|title=http://www.compressor.co.za/news/may%20news.htm]

The Unicode computer character set has dedicated symbols Unicode|㎩ (U+|33A9) for Pa and Unicode|㎪ (U+|33AA) for kPa, but these exist merely for backward-compatibility with some older ideographic character-sets and are therefore deprecated.

Uses

The pascal (Pa) or kilopascal (kPa) as a unit of pressure measurement is widely used throughout the world and largely replaces the pounds per square inch (psi) unit except in some countries still using the imperial measurement system.

Another unit for pressure measurement in common use today is millimetres of water (1 mmH2O = 9.80665 Pa).

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 (hPa) 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. Since official metrication, meteorologists in Canada use kilopascals (kPa), see for example [http://www.ctv.ca/servlet/HTMLTemplate/!ctvDynNews/Weather/Weather?City=Montreal CTV News, weather; current conditions in Montréal] and [http://www.cbc.ca/weather/conditions.jsp?station=YUL CBC weather, current conditions in Montréal] , although in some other countries hectopascals are still in use, see for example [http://www.knmi.nl/actueel/ KNMI] , [http://www.kmi.be/nederlands/index.php?menu=Menu1_3 KMI] , [http://www.dwd.de/de/WundK/W_aktuell/Beobachtungen.htm DWD] , [http://www.jma.go.jp/en/g3/index.html JMA] , [http://www.meteoam.it/modules.php?name=analisiPrevisioniSuolo MDD] and [http://weather.noaa.gov/weather/current/KDCA.html NOAA] .

: 1 hectopascal (hPa) ≡ 100 Pa ≡ 1 mbar.: 1 kilopascal (kPa) ≡ 1000 Pa ≡ 10 hPa ≡ 10 mbar.

In the former mts system, the unit of pressure is the pièze (symbol pz), which is equal to one kilopascal.

In the former cgs system, the unit of pressure is the barye (symbol ba), which is equal to one decipascal.

Vehicle owners' guides now specify tire inflation in kilopascals.

Airtightness testing of buildings is measured at 50 Pa or 0.2 inches of water.

See also

* Pascal's law
* Orders of magnitude (pressure)

References


Wikimedia Foundation. 2010.

Игры ⚽ Нужна курсовая?

Look at other dictionaries:

  • Pascal (disambiguation) — Pascal or PASCAL may refer to:People* Pascal (name), a given name or surname * Blaise Pascal (1623–1662), French mathematician and philosopherFictional characters* Pascal, the main character in the film The Red Balloon * Pascal, a character in… …   Wikipedia

  • Pascal (unit) — pascal A pressure gauge reading in psi (red scale) and kPa (black scale) Unit information Unit system: SI derived unit Unit o …   Wikipedia

  • Pascal — Pascal1 [pas kal′] n. [after PASCAL2 Blaise] 1. a high level computer language, written in structured modules: also written PASCAL 2. [p ] the basic unit of pressure in SI and MKS systems, equal to the pressure of a force of one newton per square …   English World dictionary

  • pascal — ► NOUN ▪ the SI unit of pressure, equal to one newton per square metre. ORIGIN named after the French scientist Blaise Pascal (1623 62) …   English terms dictionary

  • Pascal, Blaise — born June 19, 1623, Clermont Ferrand, France died Aug. 19, 1662, Paris French mathematician, physicist, and religious philosopher. The son of a mathematician, he was a child prodigy, earning the envy of René Descartes with an essay he wrote on… …   Universalium

  • Pascal's principle — ▪ physics also called  Pascal s Law,         in fluid (gas or liquid) mechanics, statement that in a fluid at rest in a closed container a pressure change in one part is transmitted without loss to every portion of the fluid and to the walls of… …   Universalium

  • Pressure — This article is about pressure in the physical sciences. For other uses, see Pressure (disambiguation). Pressure as exerted by particle collisions inside a closed container …   Wikipedia

  • Pascal's law — In the physical sciences, Pascal s law or Pascal s principle states that a change in the pressure of an enclosed incompressible fluid is conveyed undiminished to every part of the fluid and to the surfaces of its container. [cite book last =… …   Wikipedia

  • pressure — pressureless, adj. /presh euhr/, n., v., pressured, pressuring. n. 1. the exertion of force upon a surface by an object, fluid, etc., in contact with it: the pressure of earth against a wall. 2. Physics. force per unit area. Symbol: P Cf. stress… …   Universalium

  • pascal — A derived unit of pressure or stress in the SI system, expressed in newtons per square meter; equal to 10−5 bar or 7.50062 × 10−3 torr. [B. P.] * * * pas·cal pas kal n a unit of pressure in the mks system equivalent to one newton per square meter …   Medical dictionary

Share the article and excerpts

Direct link
… Do a right-click on the link above
and select “Copy Link”