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[Phys-L] Re: Weighing air - revisited.



I finally worked out the problem with the square law component of
volume versus pressure.

This is it: Physics educators bring many experiences with compliant
containers to the party. If your tool is a balloon, everything looks like
an inflatable.

It turns out that at the modest pressure used with the 2 liter soda bottle,
the square law component does not contribute more than one least significant
digit to the weighing at the highest pressure used.
With the higher pressure used in the one liter soda bottle, its greater
stiffness (NOT greater compliance, as one contributor thought)
counteracted the greater square law contribution.

Here are some rough n ready values for the head space growth with
pressure in a 2 liter bottle:
15 psi 12 cc
26 psi 19 cc
45 psi 45 cc
50 psi 59 cc

Brian Whatcott Altus OK Eureka!