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Topic: Air pressure

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In the News (Sun 20 Apr 14)

  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).
Weather forecasters measure air pressure with a barometer.
Barometers are used to measure the current air pressure at a particular location in "inches of mercury" or in "millibars" (mb).
kids.earth.nasa.gov /archive/air_pressure/index.html   (604 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)

 Gas Pressure
The pressure acts perpendicular (normal) to the wall; the tangential (shear) component of the force is related to the viscosity of the gas.
The pressure measured in the direction of the motion is called the total pressure and is equal to the sum of the static and dynamic pressureas described by Bernoulli's equation.
Although pressure itself is a scalar, we can define a pressure force to be equal to the pressure (force/area) times the surface area in a direction perpendicular to the surface.
www.grc.nasa.gov /WWW/K-12/airplane/pressure.html   (895 words)

 Air Pressure
The lowest sea level air pressure ever recorded was 870 mb (25.69 in.) in the eye of Typhoon (Tip) over the Pacific Ocean, whereas the highest sea level air pressure ever recorded was 1084 mb (32.01 in.) at Siberia associated with an extremely cold air mass.
The decrease of air density with altitude is accompanied by a decline in air pressure.
The height of the mercury column is a measure of the air pressure.
research.umbc.edu /~tokay/chapter5.html   (1260 words)

 Air Pressure Lesson Plans and Data
There is less air in the bottle causing unequal pressure to occur between the air in the bottle and the air outside the bottle.
The greater air pressure on the outside pushes the egg into the bottle equalizing the air pressure inside and outside the bottle.
This is due to the air pressure that is exerted downward.
www.reachoutmichigan.org /funexperiments/agesubject/lessons/tnrcc/airpressurelesson.html   (608 words)

 Physics at Minnesota:
The molecules of air are forced downward by gravity, and also are in a constant state of movement, thus causing an enormous number of collisions in one second with the outsides of the plunger and plexiglass, the Magdeburg disks, the chair and the rubber base and the 55-gallon drum.
It may be better to think of air pressure as the result of all the little pushes of the air molecules bouncing off every square inch of surface the air has contact with.
Then the atmospheric pressure will push down on the surface of the water, and since pressure is transmitted equally in all directions, it will push the water up the straw and into her mouth.
www.physics.umn.edu /outreach/pforce/airpressure.html   (3803 words)

 Air Pressure and Frontal Systems as Factors in Arctic Weather and Climate
Air pressure is a measure of the force exerted by air on all objects.
This is because a drop in air pressure often indicates that a cyclone, or low pressure system, is moving into an area, bringing clouds and precipitation.
As air masses move from one region to another, the air mass characteristics are modified by the underlying surface.
nsidc.org /arcticmet/factors/pressure.html   (1240 words)

 2003 Flight Forecast - It's All About Air Pressure
Air pressure is not the same everywhere and is continually changing.
Sometimes the air above you is denser, has more molecules per volume, and the pressure is "high." At other times the density of the air is less and the pressure is "low." There is a relationship between the air pressure and the weather (see below).
Air pressure can be measured using a number of different instruments and in a number of different units.
www.centennialofflight.gov /2003FF/pressure   (767 words)

 Understanding Air Pressure Systems for OSP Cabling
Air pressure systems were intended to protect air-core cables from water and other liquid contaminants that may penetrate sheath cracks, breaks, or leaky splice closures.
Air pressure is also supplied at selected maintenance holes (MHs) or handholes (HHs) along an underground cable route by manifolding an individual cable to a paralleling air feeder pipe that carries pressurized dry air from an air source.
Air dryers come in various sizes, and their main function is to force air into pipes at a constant rate.
www.ecmweb.com /mag/electric_understanding_air_pressure   (966 words)

 Air Pressure
Air Pressure Brian Cagle John W. Cook 10005 S. Aberdeen 8150 S. Bishop Chicago IL 60643 Chicago IL 60620 (312) 445-9347 (312) 535-3315 Objective: The main objective of the mini-teach is to demonstrate an understanding of how air pressure works.
The air outside in jar #1 is at a greater pressure than the air inside, thus forcing the water up the straw and making a fountain.
The air presses down on the sheet of newspaper, there is a lot of air pushing down on it and this is enough to stop the paper and ruler from moving.
www.iit.edu /~smile/ph9603.html   (856 words)

 USATODAY.com   (Site not responding. Last check: 2007-10-17)
Air pressure is related to its density, which is related to the air's temperature and height above the Earth's surface.
Air pressure is also called barometric pressure because barometers are used to measure it.
A bar is a force of 100,000 Newtons acting on a square meter, which is too large of a unit to be a convenient measure of Earth's air pressure.
www.usatoday.com /weather/wbarocx.htm   (779 words)

 Weather One - A Sea of Air
Because its rising, the air pressure under the bubble is a little lower than surrounding air pressure.
As the pressure on the inside continued to get lower, the air pressure on the outside stayed the same.
Higher air pressure would make the water level in the bottle higher, while lower air pressure would make the water level in the bottle lower.
www.urbanext.uiuc.edu /weather/3.html   (590 words)

 Positive Air Pressure Negative Air Pressure Air Filtration System
This system can be used to bring outdoor air through the air cleaner and create positive air pressure in the interior space.
The positive air configuration is used in the Air Handler central air systems and may be used to feed clean air into a heat exchanger or air duct.
This system can be used to move contaminated air from indoors to outdoors through the air cleaner and create negative air pressure in the indoor space.
www.airpurifiers-r-us.com /pos_neg_pressure.html   (541 words)

 Air Pressure Sensors
Minimize entry of radon gas, water vapor, and soil insecticide fumes from the soil through pores and cracks in the lowest floors by minimizing negative indoor air pressure or maintaining a slightly positive indoor air pressure.
Monitor and maintain a positive air pressure in the room of a patient with a weak immune system to minimize the entry of airborne microbes from other rooms, and from outside.
Monitor and maintain a negative air pressure in the room of a patient with infections that can be spread through the air (SARS, TB, Influenza,...) to minimize the spread of microbes to people in other rooms.
healthandenergy.com /air_pressure_sensors.htm   (963 words)

 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)

 JetStream - An Online School for Weather: Air Pressure
As elevation increases, the number of molecules decreases and the weight of air therefore is less, meaning a decrease in air pressure.
Because of this decrease in pressure with height, it makes it very hard to compare the air pressure at one location to another, especially when the elevations of each site differ.
Warm air is less dense than cooler air because the gas molecules in warm air have a greater velocity and are farther apart than in cooler air.
www.srh.noaa.gov /srh/jetstream/atmos/pressure.htm   (1172 words)

 Hot Air Balloons Buoyancy
For example, 14.7 psi is certainly enough to knock over a chair, or crush it from the top, but because the air applies roughly the same pressure from the right, left, top, bottom and all other angles, every force on the chair is balanced by an equal force going in the opposite direction.
Air density builds to whatever level balances the force of gravity, because at this point gravity isn't strong enough to pull down a greater number of particles.
This pressure level is highest right at the surface of the Earth because the air at this level is supporting the weight of all the air above it -- more weight above means a greater downward gravitational force.
www.hotairballoons.com /hotairballoon-air-pressure.asp   (828 words)

 BBC - Weather Centre - Features - Weather Basics - Air Pressure
Air pressure is the force of the air pressing down on the Earth's surface.
Near sea level there is more air above you than there would be on the top of Mount Everest, therefore the air pressure is higher near the sea than it is on the top of a mountain.
Air pressure does not only vary with height, there are many other factors, one main influence is temperature.
www.bbc.co.uk /weather/features/weatherbasics/airpressure.shtml   (445 words)

 Newton's Apple: Teacher's Guides
The air pressure holding them together was so strong that two teams of horses couldn't pull them apart; when air was let back in, the hemispheres fell apart easily.
Air pressure is created by the weight of the earth's atmosphere.
The air pressure changes daily due to the heating and cooling of the earth's surface.
www.ktca.org /newtons/10/airpressure.html   (603 words)

 Air Pressure
Air pressure at sea level is the equivalent of having many blankets, which would feel very heavy.
Air pressure also varies over time, and these temporal differences are usually caused by the temperature of the air.
The air in the atmosphere is kept close to the Earth by the pull of gravity, the force that pulls everything – including you and I – down to the ground.
www.rcn27.dial.pipex.com /cloudsrus/pressure.html   (766 words)

 BOM_Air pressure
An elongated extension of isobars away from a low pressure centre is known as a trough of low pressure.
A cold front is the delineation between cold polar air moving towards the equator and undercutting warm tropical air moving poleward.
The warm tropical air is forced to rise and become unstable with the development of large cumuliform clouds.
www.bom.gov.au /lam/Students_Teachers/pressure.shtml   (828 words)

 Household Science for Kids: Air Pressur
air as possible under the paper) so that the fold line of the newspaper is at the yardstick.
The Earth is covered in a layer of air that is nearly 80 miles thick and at sea level (the bottom) exerts or 'pushes' almost 15 pounds of pressure per square inch.
That there is this tremendous pressure of the weight of the air pushing on us every moment of every day.
www.fatlion.com /science/airpressure.html   (533 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.
The height of a mountain determines, approximately, the density of air on its summit.
www.pbs.org /wgbh/nova/everest/exposure/pressure.html   (571 words)

The pressure of the atmosphere at sea level is about 1013 millibars or 101.3 kiloPascals or 760 millimeters of mercury or 14.7 lbs/square inch or 1 atmosphere.
Sinking air in the vicinity of a high pressure center tends to suppress the upward motions required for the clouds and precipitation to develop, which is why fair weather is commonly associated with an area of high pressure.
Rising air in the vicinity of a low pressure center favors the development of clouds and precipitation, which is why cloudy weather (and likely precipitation) are commonly associated with an area of low pressure.
perth.uwlax.edu /faculty/skala/Air-Pressure.htm   (2149 words)

 Basement Air Pressure
Adjustment of air pressure should be done when the wind is calm because in typical buildings the wind pressurizes some rooms and depressurizes others.
During the following procedure, it is assumed that the air pressure sensor is located on the basement side of the basement door.
Make the face of the pressure sensor vertical so that only 0.5 Pascals (.002 inches of water column) of air pressure will be required to inflate the balloon.
healthandenergy.com /basement_air_pressure.htm   (470 words)

 Atmospheric pressure - Wikipedia, the free encyclopedia
In most circumstances atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point.
Although the pressure is constantly changing with the weather and air temperature, NASA has averaged the conditions for all parts of the earth year-round.
The following is a list of air pressures (as a fraction of one atmosphere) with the corresponding average altitude (in meters).
en.wikipedia.org /wiki/Atmospheric_pressure   (1535 words)

 Air Pressure
This indicates that the pressure of the water is the same on both sides of the cup.
The streams won’t be as strong because the pressure is smaller at higher horizontal levels in the fluid.
At the bottom of a swimming pool, the increase in pressure isn’t enough to squish you but is enough to allow you to feel the pressure on your ears.
www.physics.ucok.edu /~chughes/~cubscouts/Guides/Pressure.html   (1998 words)

 AIR PRESSURE--STRATEGY FOR THE NEW WORLD ORDER   (Site not responding. Last check: 2007-10-17)
However successful the air pressure attacks were in crippling the supply of power or in the destruction of other targets, the real impact must be judged in light of the original objective--bringing about a peace agreement.
The air pressure strategy, as applied during the Korean War, did not force the Communists to negotiate a peace agreement and thus failed to achieve it primary objective.
While air power contributed to the peace agreement, the air pressure strategy alone was not successful and its impact took much longer to be felt than the planners had originally anticipated.
www.airpower.maxwell.af.mil /airchronicles/apj/apj94/griffith.html   (3644 words)

 Air pressure - Wikipedia, the free encyclopedia
Air pressure is the pressure of the atmosphere pushing down on the earth.
Air pressure varies on the amount of air.
The more air particles the more air pressure.
en.wikipedia.org /wiki/Air_pressure   (92 words)

 Pneumatic Options Research Library: Low Pressure Air into a High Pressure Tank
Engineers can do their jobs (which is to design air motors for portability and convenience, not for efficiency) without knowing that all compressor work is lost as dissipated heat, so this vital information has been left out of textbooks for many decades to keep people from asking questions.
Because of air’s internal energy (heat that is there before and after the air is compressed), the power needed to generate compressed air is uniquely unrelated to the power available from the compressed air thus created.
The net effect is that the tank pressure will continuously go up, and a separate port (not shown) will have to be provided to vent air for use in other equipment such as to run a car, a pump, a generator, or air tools.
www.aircaraccess.com /nealtank.htm   (717 words)

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