Atmospheric pressure
Atmospheric Pressure
Atmospheric pressure (pronunciation: /æt.məˈsfɪr.ɪk ˈprɛʃ.ər/), also known as 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 101325 Pa, which is equivalent to 760 mm Hg, 29.9212 inches Hg, or 14.696 psi.
Etymology
The term "atmospheric pressure" is derived from the Greek words "atmos" meaning vapor and "sphaira" meaning sphere, combined with the Latin word "pressura" meaning pressing hard.
Definition
Atmospheric pressure is defined as the force per unit area exerted against a surface by the weight of the air above that surface in the Earth's atmosphere. In most circumstances atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point.
Measurement
Atmospheric pressure is typically measured with a barometer. In a barometer, a column of mercury in a glass tube rises or falls as the weight of the atmosphere changes. Meteorologists measure atmospheric pressure in units of atmospheres (atm).
Related Terms
- Barometer: An instrument measuring atmospheric pressure, used especially in forecasting the weather and determining altitude.
- Hydrostatic Pressure: The pressure exerted by a fluid at equilibrium at a given point within the fluid, due to the force of gravity.
- Meteorology: The study of the atmosphere, especially as it relates to weather.
See Also
External links
- Medical encyclopedia article on Atmospheric pressure
- Wikipedia's article - Atmospheric pressure
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