> > Alan, > > That's 1,058 #s external pressure. But there is also "negative" pressure > between the plates > > Doesn't this mean that (external pressure x external surface area) + > (internal "negative" pressure x internal surface area) = total force needed > to sever the two plates?"
It's been a while since my high school physics class, but if I recall correctly it's more a case of differential pressure x total surface area. I think you're probably also right about the "internal" surface area, since the area inside the gasket would be the only area affected by the vacuum. The important part is to figure the surface area that atmospheric pressure actually bears on to hold the plates together. Even if it isn't a "perfect" vacuum, even a pretty good vacuum will get close to the math. > Or, if that logic isn't right, wouldn't the vacuum have to be complete - 0 > atmospheres - in order for the entire atmospheric pressure of 1,058 #s to be > required to sever the plates? Oh, for the full 1058#, certainly. But even a "pretty good" vacuum will get close to that. It's just the differential pressure that holds the plates together. The absolute pressure isn't so important. > Doesn't help that there are no leverage points for hands to grasp onto. With > that thought, it might only take a pressure differential of maybe a pound or > two (?) to keep the jocks from victory. True. The best part of the whole thing was watching a pair of 200#+ defensive linemen get red in the face trying to pull apart a pair of 6" steel plates. _That_ was funny! > Just thinkin'. Not trying to be critical. > > So which working theory is correct? All I can tell you is one of the rules that our physics teacher pounded into our heads: Fluids cannot be pulled, only pushed. If you pull on a fluid what you get is a vacuum. If you push it then it'll find an area of lower pressure and flow there. But I do remember one time when a friend of mine put his hand over a carburettor, and it sealed there. The throttle linkage had gotten stuck and that was the first thing he could think of to keep the engine from blowing up. He had a nice barbell shaped hickey on the palm of his hand for about a week afterward where the vacuum caused blood vessels to burst. -- Aviation is more than a hobby. It is more than a job. It is more than a career. Aviation is a way of life. A second language for the world: www.esperanto.org Processor cycles are a terrible thing to waste. www.distributed.net Biofuel at Journey to Forever: http://journeytoforever.org/biofuel.html To unsubscribe, send an email to: [EMAIL PROTECTED] Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
