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[Phys-L] Re: Weighing air (Was: electricity)



But it's not found; why?

We already know it did expand -- too little and something else over
compensated?

I ask BW to take data up to (near) the limit; w/ appropriate
precautions, of course.

BTW, what is the convention? X vs Y of Y vs. X? If Y vs. X, I'd expect
an upward curve.

bc, still confused.

John Mallinckrodt wrote:

It seems to me that downward curvature of a plot of weight versus
pressure should be expected. At relatively low pressures, the
bottom, in particular, will easily expand. At higher pressures it
becomes more like the cylindrical walls; further expansion will
require the plastic itself to stretch.

Another way of saying it is that the unpressurized container does not
start in its maximum volume to surface area configuration.

John Mallinckrodt
Cal Poly Pomona



To further analyze I (one?) need(s) to know the measurement error.
Because this second set of data w/ a supposedly more compliant container
still better fits * linearly, and the power fit's exponent is sl. < one!
Either I'm confused, or the lack of precision masks the expansion, or
the gas is not ideal.

* furthermore, the new data's fit is noticeably better.

I assume the weight is linearly proportional to the pressure plus the
increase in volume, which is proportional to the pressure hence a power
law with the exponent > one.

bc, puzzled.