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Definition: atmospheric pressure from Philip's Encyclopedia

Pressure exerted by the atmosphere because of its gravitational attraction to the Earth (or other body), measured by barometers and usually expressed in units of mercury. Standard atmospheric pressure at sea level is 760mm (29.92in) of mercury or 101,325 pascals. The column of air above each cm2 of Earth's surface weighs c.1kg (or 14.7lb above each in2).


atmospheric pressure

From The Hutchinson Unabridged Encyclopedia with Atlas and Weather Guide
Pressure at any point on the Earth's surface that is due to the weight of the column of air above it; it therefore decreases as altitude increases, because there is less air above. Particles in the air exert a force (pressure) against surfaces; when large numbers of particles press against a surface, the overall effect is known as air pressure. At sea level the average pressure is 101 kilopascals (1,013 millibars, or 760 mm Hg, or 14.7 lb per sq in, or 1 atmosphere). Changes in atmospheric pressure, measured with a barometer, are used in weather forecasting. Areas of relatively high pressure are called anticyclones ; areas of low pressure are called depressions . For every square metre of a surface, a force of 10 tonnes of air pressure is exerted. This air pressure does not crush objects because they exert an equal amount of force to balance the air pressure. At higher altitudes the air is thinner and the air pressure is lower. Here, water boils at a temperature less than that at sea…
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Full text Article Atmospheric Pressure

From The Visual Guides: Understanding Weather and The Environment Full text Article EARTH'S ATMOSPHERE
Description Time Total Time Atmospheric pressure is defined as the weight of air per surface unit – that is, the force it exerts on a given surface. 00:02 - 00:10 00:01:41 Atmospheric pressure can be measured with a mercury barometer. 00:11 - 00:15 A mercury barometer is made of a tube from which…
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Full text Article atmospheric pressure

From Astronomy Encyclopedia
Force exerted by the gas forming an atmosphere on a unit area. The units are pascals (Pa), with 1 Pa = 1 N/m 2 . Commonly encountered non-SI units are the bar or millibar (1 bar = 10 5 Pa) and the atmosphere (1 Atm = 101,325 Pa). Sea-level pressure on the Earth is around 10 5 Pa, surface pressures…
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Full text Article atmospheric pressure

From The Hutchinson Unabridged Encyclopedia with Atlas and Weather Guide
Pressure at any point on the Earth's surface that is due to the weight of the column of air above it; it therefore decreases as altitude increases, because there is less air above. Particles in the air exert a force (pressure) against surfaces; when large numbers of particles press against a…
| 309 words
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Full text Article atmospheric pressure

From Britannica Concise Encyclopedia
Force per unit area exerted by the air above the surface of the Earth. Standard sea-level pressure, by definition, equals 1 atmosphere (atm), or 29.92 in. (760 mm) of mercury, 14.70 lbs per square in., or 101.35 kilopascals, but pressure varies with elevation and temperature. It is usually measured…
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Full text Article atmospheric pressure

From The Hutchinson Unabridged Encyclopedia with Atlas and Weather Guide
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Full text Article atmospheric pressure

From Collins Dictionary of Astronomy
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Full text Article atmospheric pressure

From The Penguin Dictionary of Science
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Full text Article atmospheric pressure

From The New Dictionary of Cultural Literacy, Houghton Mifflin
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Full text Article atmospheric pressure

From Philip's Encyclopedia
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Full text Article atmospheric pressure

From The American Heritage Student Science Dictionary
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