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Inch of mercury facts for kids

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Rare American Barometer, Lyman King, Clifton Springs, New York, c. 1860 - Museum of Science and Industry (Chicago) - DSC06342
Early American barometer calibrated in inches of mercury

Inches of mercury, inHg or Hg is a non-SI unit for pressure, or a way to measure how hard something is pushing on something else. It is a unit that is still used a lot for counting barometric pressure, or how thick the air is in one place, in weather forecasts and aviation, or anything that has to do with flying in the United States, but is considered a bit old in other countries.

It is the amount of pressure that a column of mercury that is one inch tall has at 32 °F (0 °C) at the standard acceleration of gravity, or how fast things speed up as they are falling because of gravity.

1 inHg = 3,386.389 pascals at 0 °C.

Airplanes that are flying at high altitudes, or that are flying higher than what is called the Transition Altitude, which varies by country set their barometric altimeters, which control the air pressure in their plane, to a standard pressure of 29.92 inHg or 1,013.2 hPa (1 hPa = 1 mbar) no matter what the actual sea level pressure is, in inches of mercury used in the U.S. and Canada, and in other units in other countries. The resulting altimeter readings, or the things that show up on the plane's altimeter are known as flight levels.

Related pages

  • Torr (millimeters of mercury)

See also

Kids robot.svg In Spanish: Pulgada de mercurio para niños

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