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Atmospheric pressure, also known as air pressure or barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as 101,325 Pa (1,013.25 hPa ), which is equivalent to 1,013.25 millibars , [ 1 ] 760 mm Hg , 29.9212 inches Hg , or 14.696 psi . [ 2 ]
at each geopotential altitude, where g is the standard acceleration of gravity, and R specific is the specific gas constant for dry air (287.0528J⋅kg −1 ⋅K −1). The solution is given by the barometric formula. Air density must be calculated in order to solve for the pressure, and is used in calculating dynamic pressure for moving vehicles.
Since 1982, STP has been defined as a temperature of 273.15 K (0 °C, 32 °F) and an absolute pressure of exactly 10 5 Pa (100 kPa, 1 bar). NIST uses a temperature of 20 °C (293.15 K, 68 °F) and an absolute pressure of 1 atm (14.696 psi, 101.325 kPa). [ 3 ] This standard is also called normal temperature and pressure (abbreviated as NTP).
US customary units. 14.69595 psi. other metric units. 1.013250 bar. Aneroid barometer for household use from c. 1925. The standard atmosphere (symbol: atm) is a unit of pressure defined as 101 325 Pa. It is sometimes used as a reference pressure or standard pressure. It is approximately equal to Earth 's average atmospheric pressure at sea level.
SI units. 6.894757 kPa. The pound per square inch (abbreviation: psi) or, more accurately, pound-force per square inch (symbol: lbf/in2), [ 1 ] is a unit of measurement of pressure or of stress based on avoirdupois units. It is the pressure resulting from a force with magnitude of one pound-force applied to an area of one square inch.
Barometer. A barometer is a scientific instrument that is used to measure air pressure in a certain environment. Pressure tendency can forecast short term changes in the weather. Many measurements of air pressure are used within surface weather analysis to help find surface troughs, pressure systems and frontal boundaries.
1.5 psi Pressure increase per meter of a water column [26] 10 kPa 1.5 psi Decrease in air pressure when going from Earth sea level to 1000 m elevation [citation needed] +13 kPa +1.9 psi High air pressure for human lung, measured for trumpet player making staccato high notes [48] < +16 kPa +2.3 psi
0.019 336 77 psi. The torr (symbol: Torr) is a unit of pressure based on an absolute scale, defined as exactly 1 760 of a standard atmosphere (101325 Pa). Thus one torr is exactly 101325 760 pascals (≈ 133.32 Pa). Historically, one torr was intended to be the same as one "millimeter of mercury", but subsequent redefinitions of ...