Agent Orange: Friendly fire that keeps on burning. | some 200 years BC. He was given the problem to pump from a well deeper than 30 feet (our modern measure -- not sure of what he measured in). No matter how precisely he made the pump, if the cylinder was placed at ground level, it wouldn't suck up the water in the well as the depths approached 30 feet. He finally figured out that a vacuum realy does nothing -- it is the pressure on the fluid you're trying to lift that rushes in to fill the vacuum that does the work. Given that atmospheric pressure is limited to about 30 inches of Hg, 30 feet is the most you will ever pull water. Now further consider that when you are above seal level, you need to adjust the barometer to compensate for your altitude, and 30 inches of Hg isn't really 30 inches, but some less. In the instance cited above; if you were in the bottom of the Death Valley and there was a high pressure system sitting over you, then you may be able to make 31"+ of vacuum. The real work you can do with a vacuum depends on how much air pressure is on you at the time, and it will normally be quite a bit less than 30" |
Gasoline tank disposal
