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

[Bernard Cleyet <anngeorg@PACBELL.NET>]

"p.s. Care obviously needed with inflation)"


A method:  nearly fill soda bottle w/ water; cover with towels, or place
in strong box and pump up till it explodes (use tire pump that includes
gauge -- e.g. those combo 12 V. batts. and pump)  then pump another
identical (not quite the correct word) to somewhat lower pressure for
"weighing".

Doing several will be statistically interesting.

bc, who bottled his beer waited for one burst, then refrigerated.

Brian Whatcott wrote:

> Building on Vickie's suggestion. I recall that thin plastic soda bottles
> can handle about 50 psi.
>
> If one drills a hole in a cap, and screws in a threaded tire valve
> (available at many autoparts stores for go-faster alloy wheels)
> Then one could compare the weight of the bottle at ambient
>  pressure, and one inflated to 15 psi, even 30 psi, using a digital
>  postal balance.
>
> This would give a reasonably plausible result, quite cheaply.
>
> Brian Whatcott
> p.s. Care obviously needed with inflation)
>
> At 10:58 AM 2/4/2005, you wrote:
>
>
> > Actually, the two balloons on a meter stick doesn't even show that, b=
> > ecause of the phenomenon of the buoyant force. =20
> >
> > One "right" way to weigh air (in principle) is to take a vacuum bell =
> > jar, weigh it on a sensitive balance, pump it out, seal it off, and w=
cut