Pascal

From Wikipedia, the free encyclopedia.

For other uses, see Pascal (disambiguation).

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The pascal (symbol: Pa) is the SI unit of pressure. It is equivalent to one newton per square metre. The same unit is also used for stress, Young's modulus, and tensile strength.

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

Definition

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

SI multiples

Multiple	Name	Symbol		Multiple	Name	Symbol
100	pascal	Pa
101	decapascal	daPa		10–1	decipascal	dPa
102	hectopascal	hPa		10–2	centipascal	cPa
103	kilopascal	kPa		10–3	millipascal	mPa
106	megapascal	MPa		10–6	micropascal	µPa
109	gigapascal	GPa		10–9	nanopascal	nPa
1012	terapascal	TPa		10–12	picopascal	pPa
1015	petapascal	PPa		10–15	femtopascal	fPa
1018	exapascal	EPa		10–18	attopascal	aPa
1021	zettapascal	ZPa		10–21	zeptopascal	zPa
1024	yottapascal	YPa		10–24	yoctopascal	yPa

Origin

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

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 (ISO 2533).

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 ㎩ for Pa and ㎪ for kPa, but these exist merely for backward-compatibility with some older ideographic character sets.

Comparison to other units of pressure

1 bar	100 000 Pa
1 barye	0.1 Pa
1 millibar	100 Pa
1 atmosphere	101 325 Pa
1 mmHg (or Torr)	133.322 Pa
1 inHg	3386.833 Pa
1 cmH2O	98.0638 Pa

Pressure units and conversion factors

	Pa	bar	at	atm	Torr	psi
1 Pa	≡ 1 N/m²	= 10−5 bar	≈ 10.2·10−6 at	≈ 9.87·10−6 atm	≈ 7.5·10−3 Torr	≈ 145·10−6 psi
1 bar	= 100 000 Pa	≡ 106 dyn/cm²	≈ 1.02 at	≈ 0.987 atm	≈ 750 Torr	≈ 14.504 psi
1 at	= 98 066.5 Pa	= 0.980665 bar	≡ 1 kgf/cm²	≈ 0.968 atm	≈ 736 Torr	≈ 14.223 psi
1 atm	= 101 325 Pa	= 1.01325 bar	≈ 1.033 at	≡ 101 325 Pa	= 760 Torr	≈ 14.696 psi
1 Torr	≈ 133.322 Pa	≈ 1.333·10−3 bar	≈ 1.360·10−3 at	≈ 1.316·10−3 atm	≡ 1 mmHg	≈ 19.337·10−3 psi
1 psi	≈ 6894.757 Pa	≈ 68.948·10−3 bar	≈ 70.307·10−3 at	≈ 68.046·10−3 atm	≈ 51.7149 Torr	≡ 1 lbf/in²

See also

• Orders of magnitude (pressure)