21 Jun 07 21:19, DAVID WILLIAMS wrote to Roy Witt:

 DW> -> What keeps the can from collapsing is the tapered form at the top
 DW> and -> bottom. Also, as you say, the pressure inside keeps the walls
 DW> under -> tension, until the pressure is relieved. But it's the fact
 DW> that liquid -> can't be compressed that makes the can rigid. Once
 DW> there is an exit place -> for liquid to flow, it will no longer stop
 DW> the can from collapsing.

 DW> That would be true if the can were absolutely full of liquid. But I'm
 DW> sure that, in most cases at least, there is some gas at the top.
 DW> That's why an unopened can makes a sloshing sound if shaken. The gas
 DW> is compressible, so the can can be compressed at least slightly, if
 DW> enough pressure is applied. But, since the gas is at quite high
 DW> pressure, this is not easy.

If the gas is under high pressure, it's exerting an equal force on the
liquid, which can't be compressed.

                R\%/itt


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