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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]
The units of atmospheric pressure commonly used in meteorology were formerly the bar (100,000 Pa), which is close to the average air pressure on Earth, and the millibar. Since the introduction of SI units, meteorologists generally measure atmospheric pressure in hectopascals (hPa), equal to 100 pascals or 1 millibar.
Comparison of a graph of International Standard Atmosphere temperature and pressure and approximate altitudes of various objects and successful stratospheric jumps The International Standard Atmosphere ( ISA ) is a static atmospheric model of how the pressure , temperature , density , and viscosity of the Earth's atmosphere change over a wide ...
When pressure falls, the mercury moves back, lifting the float and turning the dial the other way. [19] Around 1810 the wheel barometer, which could be read from a great distance, became the first practical and commercial instrument favoured by farmers and the educated classes in the UK.
Pressure of an average human bite [citation needed] 2.8–8.3 MPa 400–1,200 psi Pressure of carbon dioxide propellant in a paintball gun [64] 5 MPa 700 psi Water pressure of the output of a coin-operated car wash spray nozzle [58] 5 MPa 700 psi Military submarine max. rated pressure (est.) of Seawolf-class nuclear submarine, at depth of 500 m ...
The new value is the mean atmospheric pressure at an altitude of about 112 metres, which is closer to the worldwide median altitude of human habitation (194 m). [ 10 ] Natural gas companies in Europe, Australia, and South America have adopted 15 °C (59 °F) and 101.325 kPa (14.696 psi) as their standard gas volume reference conditions, used as ...
For gases, pressure is sometimes measured not as an absolute pressure, but relative to atmospheric pressure; such measurements are called gauge pressure. An example of this is the air pressure in an automobile tire, which might be said to be "220 kPa (32 psi)", but is actually 220 kPa (32 psi) above atmospheric pressure. Since atmospheric ...
In science and engineering the study of high pressure examines its effects on materials and the design and construction of devices, such as a diamond anvil cell, which can create high pressure. High pressure usually means pressures of thousands (kilo bars ) or millions (megabars) of times atmospheric pressure (about 1 bar or 100,000 Pa).