Glenn Elert
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The Physics Factbook™
Edited by Glenn Elert -- Written by his students
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| Bibliographic Entry | Result (w/surrounding text) |
Standardized Result |
|---|---|---|
| Zitzewitz, Paul & Robert Neff. Physics. New York: Glencoe, 1995: 267. | "Standard Atmosphere 1 × 105 Pa Best Vacuum 1 × 10-12 Pa" |
1 × 10-20 g/cm3 |
| >McAllister, Robert. McAllister Technical Services. Electronic Mail. 24 March 1997. | "Pressures of 5 × 10-11 torr are not uncommon in everyday science labs" | 8 × 10-17 g/cm3 |
| Sears & Zemansky. University Physics, Complete Edition. Menlo Park, CA: Addison Wesley, 1962: 315, 694. | "Density of air 1.29 × 10-3 g/cm3 at STP … pressures as low as 10-8 Pa" | 1 × 10-16 g/cm3 |
A vacuum theoretically is a space devoid of matter. A vacuum is a volume from which practically all air has been exhausted. A perfect vacuum has never been made. In order to find the density of a laboratory vacuum, I needed to use the following ratio:
density of vacuum/density at STP = pressure of vacuum/pressure at STP
Where STP is standard temperature and pressure. The reason I needed to use the ratio was because a vacuum is usually measured by its pressure and not its density. The density of air at STP is 1.29 × 10-3 g/cm3 and the pressure of air at one standard atmosphere is 101,325 pascals. To find the density, I used a value for the vacuum pressure found in each source and plugged it into the formula. For example:
density of vacuum/1.29 × 10-3 g/cm3 = 10-12
Pa/ 105 Pa
density of vacuum = 1.29 × 10-20 g/cm3
Mesah Harwood -- 1999
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