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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 ]
Atmospheric pressure is the total weight of the air above unit area at the point where the pressure is measured. Thus air pressure varies with location and weather . If the entire mass of the atmosphere had a uniform density equal to sea-level density (about 1.2 kg/m 3 ) from sea level upwards, it would terminate abruptly at an altitude of 8.50 ...
The standard atmosphere was originally defined as the pressure exerted by a 760 mm column of mercury at 0 °C (32 °F) and standard gravity (g n = 9.806 65 m/s 2). [2] It was used as a reference condition for physical and chemical properties, and the definition of the centigrade temperature scale set 100 °C as the boiling point of water at this pressure.
Loudness is the subjective experience of sound pressure and is measured as a sound pressure level (SPL) on a logarithmic scale of the sound pressure relative to some reference pressure. For sound in air, a pressure of 20 μPa is considered to be at the threshold of hearing for humans and is a common reference pressure, so that its SPL is zero.
Pressure as a function of the height above the sea level. There are two equations for computing pressure as a function of height. The first equation is applicable to the atmospheric layers in which the temperature is assumed to vary with altitude at a non null lapse rate of : = [,, ()] ′, The second equation is applicable to the atmospheric layers in which the temperature is assumed not to ...
The air pressure is just enough to feel glorious around the eye socket, without putting pressure on the eye, itself, but there are various settings and levels to suit your sensitivity. The heat ...
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In honour of Torricelli, the torr was defined as a unit of pressure equal to one millimeter of mercury at 0 °C. However, since the acceleration due to gravity – and thus the weight of a column of mercury – is a function of elevation and latitude (due to the rotation and non- sphericity of the Earth), this definition is imprecise and varies ...