92_Atmospheric_pressure

92_Atmospheric_pressure - sea level pressure is 29.92 inHg...

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INDIANA UNIVERSITY, DEPARTMENT OF PHYSICS, P309 LABORATORY Auxiliary Lab #92: Atmospheric Pressure Goal: Determine the ambient pressure in the lab Pressure units: 1 Pa (Pascal) = 1N/m 2 1 mbar = 1 hPa (hektoPascal) = 100 Pa 1 cmHg = 1333.2 Pa 1 in.Hg = 3386.4 Pa First, get the current Bloomington pressure by calling the Automated Weather Service (825-8046) or using the web ( www.hutchison.org/allen/weather ). The number you get is around 30.00 and is the pressure in in.Hg that one would measure in Bloomington if one were at sea level and if the temperature were 15 o C (or 59 o F). This is the so-called sea- level pressure (P SL ). The pressure and the temperature change with altitude. Often, a model is used, the “Standard Atmosphere”, that is reasonably close to the truth. In this model, the standard
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Unformatted text preview: sea level pressure is 29.92 inHg, and with increasing altitude above sea level, the pressure decreases by ∆ p and the temperature by ∆ T for every 1000 ft in elevation as follows: Elevation (ft above sea level)) ∆ p (per 1000 ft) (in.Hg) ∆ T (per 1000 ft) ( F) ( C) 0 – 1000 -1.06 -3.6 -2.0 1000 – 2000 -1.04 -3.5 -2.0 2000 – 3000 -1.00 -3.6 -2.0 3000 – 4000 -0.98 -3.6 -2.0 In order to convert this pressure to the pressure in the lab, the temperature is irrelevant, but we have to know the altitude h of the lab. The elevation of the first floor of Swain Hall is h Swain =800 ft (above sea level) The ambient pressure in the lab is then obtained by ft ft h inHg inHg P inHg P Swain SL lab 1000 ) ( 06 . 1 ) ( ) ( ⋅ − = Finally, convert to the desired units. 92 - 1...
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This note was uploaded on 01/20/2012 for the course P 309 taught by Professor Urheim during the Spring '11 term at Indiana.

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