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Topic: Atmospheric pressure


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In the News (Wed 24 Apr 19)

  
  Atmospheric Pressure: force exerted by the weight of the air
Atmospheric pressure is defined as the force per unit area exerted against a surface by the weight of the air above that surface.
Atmospheric pressure is measured with an instrument called a "barometer", which is why atmospheric pressure is also referred to as barometric pressure.
Meteorologists use a metric unit for pressure called a millibar and the average pressure at sea level is 1013.25 millibars.
ww2010.atmos.uiuc.edu /(Gh)/guides/mtr/fw/prs/def.rxml   (257 words)

  
 atmospheric pressure at sea level : Search Results : GoodSearch : Search the Internet with GoodSearch and support your ...
Atmospheric pressure is less at high altitudes than at sea level or more normal elevations.
Atmospheric (air) pressure at sea level will support a column of mercury that is...
pressure at the new altitude and Po represents the atmospheric pressure at sea level.
www.goodsearch.com /Search.aspx?Keywords=atmospheric+pressure+at+sea+level&page=8   (302 words)

  
 Highbeam Encyclopedia - Search Results for Atmospheric pressure
atmospheric pressure 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.
pressure exerted by a vapor that is in equilibrium with its liquid.
atmospheric pressure distribution in which there is a low central pressure relative to the surrounding pressure.
www.encyclopedia.com /SearchResults.aspx?Q=Atmospheric+pressure   (804 words)

  
 UK's National Pressure Standards - Pressure modes
Whatever pressure units you are using, if you want to follow internationally agreed and recognised conventions (recommended!) a descriptive word should be used to denote the pressure mode and not a letter.
Pressures measured on a scale which uses this zero value as their reference point are said to be absolute pressures.
Pressure modes are illustrated in the diagram; note that the reference line for gauge-mode measurements is not straight, illustrating the changeable nature of atmospheric pressure.
www.npl.co.uk /pressure/faqs/modes.html   (808 words)

  
 7(d) Atmospheric Pressure
In this graph, air pressure at the surface is illustrated as being approximately 1013 millibars (mb) or 1 kilogram per square centimeter of surface area.
Atmospheric pressure then forced the mercury up into the tube to a level that was considerably higher than the mercury in the container.
Atmosphere pressure values are adjusted for elevation and are described relative to sea-level.
www.physicalgeography.net /fundamentals/7d.html   (821 words)

  
 NOVA Online | Everest | Atmospheric Pressure
Pioneering scientists discovered atmospheric pressure (also known as barometric or air pressure) in the 17th century, and determined a startling new fact—that air actually has weight.
Evangelista Torricelli, one of the first to discover atmospheric pressure, once said, "We live submerged at the bottom of an ocean of the element air." The Earth's gravitational field is pulling on air, and this pull, or "pressure" of air, is called atmospheric pressure.
In fact, meteorologists monitor atmospheric pressure at the Earth's surface in order to determine whether the pressure is rising or falling, which helps to predict weather patterns.
www.pbs.org /wgbh/nova/everest/exposure/pressure.html   (571 words)

  
  Atmospheric pressure - Encyclopedia of Earth
Atmospheric pressure then forced the mercury up into the tube to a level that was considerably higher than the mercury in the container.
Torricelli determined from this experiment that the pressure of the atmosphere is approximately 30 inches or 76 centimeters (one centimeter of mercury is equal to 13.3 millibars).
Atmosphere pressure values are adjusted for elevation and are described relative to sea-level.
www.eoearth.org /article/Atmospheric_pressure   (891 words)

  
  Pressure - MSN Encarta
The unit atmosphere (atm) is defined as a pressure of 1.03323 kg/sq cm (14.696 lb/sq in), which, in terms of the conventional mercury barometer, corresponds to 760 mm (29.921 in) of mercury.
Pressures in the range of millions of kilograms per square centimeter have been obtained for experimental purposes and for the manufacture of artificial diamonds, where pressures of about 70,000 kg/sq cm (about 1 million lb/sq in), together with temperatures in excess of 2770° C (5000° F), are required.
In the atmosphere the total pressure (atmospheric pressure) is equal to the sum of the partial pressures of its constituents (oxygen, nitrogen, carbon dioxide, and rare gases).
encarta.msn.com /encyclopedia_761563312/Pressure.html   (669 words)

  
  Atmospheric pressure - Wikipedia, the free encyclopedia
Atmospheric pressure varies widely on the Earth, and these variations are important in studying weather and climate.
Atmospheric pressure is often measured with a mercury barometer, and a height of approximately 760 mm (30 inches) of mercury is often used to teach, make visible, and illustrate (and measure) atmospheric pressure.
In terms of city water pressure, one atmosphere is approximately one-half to one-fifth the pressure of typical city water mains (i.e., water pressure is around 2 to 5 atmospheres).
en.wikipedia.org /wiki/Atmospheric_pressure   (1171 words)

  
 Pressure - Wikipedia, the free encyclopedia
Pressure (symbol: p) is the force per unit area acting on a surface in a direction perpendicular to that surface.
Pressure is still sometimes expressed in kgf/cm² or grams-force/cm² (sometimes as kg/cm² and g/cm² without properly identifying the force units).
Because pressure is commonly measured by its ability to displace a column of liquid in a manometer, pressures are often expressed as a depth of a particular fluid (e.g.
en.wikipedia.org /wiki/Pressure   (1542 words)

  
 Pressure
Since static fluid pressure is determined by the fluid density and depth, the depth or height difference of a given liquid is commonly used for pressure measurement:
The fundamental SI unit of pressure is the Pascal (Pa), but it is a small unit so kPa is the most common direct pressure unit for atmospheric pressure.
The mercury barometer is the standard instrument for atmospheric pressure measurement in weather reporting.
hyperphysics.phy-astr.gsu.edu /hbase/pman.html   (538 words)

  
 Atmospheric Pressure
Pressure is a force, or weight, exerted on a surface per unit area, and is measured in Pascals (Pa).
The pressure exerted by a kilogram mass on a surface equals 9.8 Pa. The pressure exerted by the whole atmosphere on the Earth’s surface is approximately 100,000 Pa. Usually, atmospheric pressure is quoted in millibars (mb).
In fact, the air moving from high to low pressure follows a spiralling route due to the rotation of the Earth beneath the moving air, which causes an apparent deflection of the wind to the right in the Northern Hemisphere, and to the left in the Southern Hemisphere.
www.ace.mmu.ac.uk /eae/Weather/Older/Pressure.html   (421 words)

  
 [No title]   (Site not responding. Last check: 2007-10-07)
Atmospheric pressure measurements are unique among the meteorological variables that can be measured at a single site on the surface of Mars, providing the widest ranging study of phenomena and of space and time scales.
Atmospheric pressure on Mars is approximately 1% of that on Earth and varies about plus/minus 15% during the year due to condensation and sublimation of its primarily CO2 atmosphere on to and from its polar caps.
Atmospheric pressure is defined as the force per unit area exerted against a surface by the weight of the air molecules above that surface.
www.lycos.com /info/atmospheric-pressure.html   (451 words)

  
 atmospheric pressure
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.
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).
A standard measurement for atmospheric pressure at sea level is a column of mercury 760 mm/30 in high.
www.tiscali.co.uk /reference/encyclopaedia/hutchinson/m0025299.html   (434 words)

  
 Pressure
The pressure measured by the most common types of pressure instruments is a gauge pressure since these instruments indicate the pressure relative to atmospheric pressure.
This requires a dynamic pressure less than 1% of the ambient pressure, so that at sea level where the density of air is about 1.2 kg/m^3 we are limited to velocities less than 40 m/s (132 ft/s or 90 mph), which corresponds to a Mach number of about 0.12.
This pressure difference is caused by the fact that the average velocity over the upper surface of the airfoil is somewhat greater than the average velocity over the lower surface (remember that a higher velocity corresponds to a lower pressure).
www.princeton.edu /~asmits/Bicycle_web/pressure.html   (1368 words)

  
 LOW ATMOSPHERIC PRESSURE - Electromagnetic Theory
When the positively polarized atmosphere is magnetically rejected by the internal phenomenon it produces a decrease in the pressure it exerts over the area of the surface creating then a LOW ATMOSPHERIC PRESSURE ZONE, previous condition for the formation of storms, tornadoes and hurricanes.
When the weight of the atmosphere over the surface decrease in a given zone, due to the closiness of the nucleus protuberance, clouds flow toward that area because in nearby zones atmospheric pressure is greater and clouds formations always will displace or flow toward the lower resistance zone, which is the low atmospheric pressure zone.
In a low atmospheric pressure zone, an extraordinary negative electric discharge increases the possibilities to evolve toward a bigger dimensions phenomenum such as a storm, a hurricane or a tornadoe.
www.costarricense.cr /pagina/fvitoria/pressure.html   (991 words)

  
 Pressure - Engineering   (Site not responding. Last check: 2007-10-07)
Pressure is sometimes measured, not as an absolute pressure, but relative to atmospheric pressure; such measurements are sometimes called gauge pressure.
The pressure of a moving fluid can be measured using a Pitot probe, or one of its variations such as a Kiel probe or Cobra probe, connected to a manometer.
A rule of thumb commonly used by scuba divers is that one atmosphere is approximately equal to the pressure exerted by ten metres of water.
engineering.wikia.com /wiki/Pressure   (1152 words)

  
 Pressure   (Site not responding. Last check: 2007-10-07)
The atmosphere at the equator is heated by the overhead sun and contact with the heated surface.
Atmospheric pressure forced the mercury to rise in the tube and provided the means to gauge pressure.
The atmospheric pressure observation is the principal weather element used in forecasting weather.
pao.cnmoc.navy.mil /pao/Educate/WeatherTalk2/indexpressure.htm   (452 words)

  
 Atmospheric Pressure   (Site not responding. Last check: 2007-10-07)
Pressure is equal to the force acting on an object divided by the area upon which it is acting.
Atmospheric pressure is sometimes expressed in terms of the number of inches in a column of Mercury that are supported by the downward push of the atmosphere.
Atmospheric pressure decreases with height above the surface of a planet because there is less total mass in the atmosphere above a reference point as the height of the reference point increases.
www-star.stanford.edu /projects/mod-x/id-pres.html   (1478 words)

  
 Atmospheric Pressure
The pressure exerted by a kilogram mass on the Earth's surface is approximately 10 Pa. The pressure exerted by the whole atmosphere on the Earth’s surface is approximately 100,000 Pa.
This older form of measurement is related to the traditional method of measuring atmospheric pressure using a mercury barometer.
Variations in atmospheric pressure lead to the development of winds that play a significant role in shaping our daily weather.
www.ace.mmu.ac.uk /eae/Atmosphere/Older/Pressure.html   (234 words)

  
 Atmospheric pressure   (Site not responding. Last check: 2007-10-07)
Atmospheric pressure is the amount of force exerted over a surface area, caused by the weight of air molecules above it.
The standard value for atmospheric pressure at sea level is: 29.92 inches or 760 millimeters of mercury.
An aneroid barograph consists of a revolving drum on which the air pressure is recorded, a syphon cell that expands or contracts as air pressure rises and falls, and a lever that transfers the movement of the syphon cell to the recording pen that writes on the revolving drum.
www.centennialofflight.gov /essay/Dictionary/Atmos_pressure/DI140.htm   (276 words)

  
 Atmospheric pressure Summary
The measured value of the atmospheric pressure fluctuates slightly in response to moving weather systems, and it drops as one ascends to higher elevations, since less air is overhead to exert a downward force.
Atmospheric pressure is often measured with a mercury barometer, and a height of approximately 760 mm (30 inches) of mercury is often used to teach, make visible, and illustrate (and measure) atmospheric pressure.
In terms of city water pressure, one atmosphere is approximately one-half to one-fifth the pressure of typical city water mains (i.e., water pressure is around 2 to 5 atmospheres).
www.bookrags.com /Atmospheric_pressure   (2330 words)

  
 Atmospheric Pressure: The force exerted by the weight of air
ir pressure is the force exerted on you by the weight of tiny particles of air (air molecules).
Barometers are used to measure the current air pressure at a particular location in "inches of mercury" or in "millibars" (mb).
Earth's atmosphere is pressing against each square inch of you with a force of 1 kilogram per square centimeter (14.7 pounds per square inch).
kids.mtpe.hq.nasa.gov /archive/air_pressure   (604 words)

  
 Atmospheric Pressure - Microwave Encyclopedia - Microwaves101.com
Atmospheric pressure is important because lower air pressure means that voltage breakdown occurs at lower electric field strength.
There are many units of pressure, including millimeters of mercury (same as a Torr), inches mercury, inches of water, Torr, Pascals (and kilo-Pascals and mega-Pascals because a Pascal is so tiny).
At 100,000 feet, pressure is about 1% of what it is at sea level.
www.microwaves101.com /encyclopedia/atmosphericpressure.cfm   (282 words)

  
 Teachers' Domain: Atmospheric Pressure
Thus, atmospheric pressure is lower on a mountaintop than it is at sea level.
Though the concentration of oxygen in the air is the same throughout the troposphere (the layer of the atmosphere in which we all live), there is less total gas per unit of volume in air at the top of a mountain than in air at sea level.
This sister's physiological altitude, then, is several hundred meters higher than her twin's actual altitude: the atmospheric pressure is lower and the air is thinner.
www.teachersdomain.org /resources/phy03/sci/phys/mfw/pressure   (498 words)

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