Posted by:
LarryF
at Thu Mar 16 15:08:55 2006 [ Email Message ] [ Show All Posts by LarryF ]
>>Would 50 pounds per square inch be the same as 100 pounds per two square inches and 200 pounds per four square inches?
Exactly. Divide your forces in Pounds by the area in Sqaure Inches and you get 50 Pounds per Square Inch (psi) in all 3 cases.
>>It would make sense that it would but the difference between PSI, force, and pressure mentioned before had me thinking this all sounds too much like pressure.
Just to be clear, I was discussing exactly two quantities in the earlier thread: 1) Force 2) Pressure
PIS is not a third quantity, it is the English unit of pressure.
>>The recent giant snake special mentioned the anaconda was exherting 90 pounds per square inch on the live duck. The total snake (or surface they were measuring) was then exherting 9000 pounds "of pressure" on this duck.
They were using the common informal English usage of the word "pressure" which is used interchangeably with the word "force". In a more formal context, "pressure" and "force" are two disting quantities. Thus much of the confusion above.
>>You would think the things head would pop right off or it would just explode. I have heard lots of bones cracking from constrictors prey before but 9000 lbs seems like quite a bit.
They got that number by reversing what you did above, except that in this case they are adding up all the forces on all parts of the duck pushing in different directions (multiplying 90 p/si by an estimated 100 si to get 9000 p). The result is a number that sounds impressive but is of almost no real significance. The significant quantity here is the 90 psi.
That does sound like a lot of pressure, but I don't have a feel for how close that is to making the duck's head explode. I have seen eyes literally pop out o the sockets of mice and rats while being constricted...
P.S. Note that in that show Dr. Barr was actually using a pressure gauge attached to an air filled bladder and correctly stating the result in terms of "psi". In his "Bite Force" show, he uses a force gauge and correctly referrs to the result in terms of "pounds". In every other similar show I can think of a force gauge was used and the result incorrectly given in "psi" which makes no sense whatsoever, thus more confusion.
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