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Post by millring on Oct 12, 2006 20:28:30 GMT -5
Okay, say you have a sphere that is just about 1 cubic inch in interior volume. That sphere, and the air inside that sphere, is at room temp -- let's call it 70 degrees F.
Now let's say we had access to a pottery kiln and heated the sphere up to 2400 degrees F. All through that heating process the interior air is capable of escaping the interior of the sphere.
But suddenly, within seconds of the peak temperature, some god-like potter decides that this is the exact moment in the creative process to shut off the kiln -- and with that shutting off of the kiln, the air inside the sphere can neither escape, nor can more air get into the sphere.
What is the interior pressure of the sphere? Does one measure vacuum in psi? What -- on a scale from black hole to exploding marshmallows in a microwave -- is the severity of the interior condition of the sphere?
Let's say just for the fun of it that the sphere was pottery. Would a potter -- pretend you know one -- be worried about the potential energy stored in that sphere?
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Post by Village Idiot on Oct 12, 2006 20:31:48 GMT -5
I think Kim Jong Il was wondering the same thing last week. Start lobbing those spheres in any direction, Millring, and Cribbs will most likely impose some serious sanctions.
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Post by aquaduct on Oct 12, 2006 21:36:04 GMT -5
OK, start with pV=nRT.
Since the trip from 294 K to 1589 K is done at constant volume and pressure, the number of moles in the sphere will be reduced about 5.5 times.
Then it's sealed so n and V stay the same as T descends, leaving pressure to decrease by the same 5.5 times.
Meaning the the basic 1 atmosphere pressure (~14.7 psi) will be reduced to ~2.7 psi, meaning you're pulling about 12 psi vacuum relative to atmospheric.
Given the structural strength of a ceramic sphere, on a scale from black hole to exploding marshmallows, this would rank about with waiting for a ball bearing to implode. I would imagine you wouldn't even notice if you poked a hole in it.
Go back to sleep, John, it'll be alright.
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Post by TDR on Oct 12, 2006 21:56:32 GMT -5
I got stuck at the part about the god-like potter. Where are you gonna find one of those?
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Post by dradtke on Oct 12, 2006 22:14:13 GMT -5
So which is correct?
god like potter
god-like potter
god like-potter
god-like-potter
Just wondering...
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Post by aquaduct on Oct 12, 2006 22:53:25 GMT -5
So which is correct? god like potter god-like potter god like-potter god-like-potter Just wondering... I think a recent episode of Mythbusters proved that none of them were plausible. |
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Post by Cosmic Wonder on Oct 12, 2006 22:57:06 GMT -5
John, if the sphere shards come out in the shape of the face of Jesus, you can sell them on ebay.
Mike
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Post by Marshall on Oct 12, 2006 23:16:17 GMT -5
How thick are the walls of the sphere ?
Peter's calc gives the pressure inward; which is resisited by compression in the walls of the sphere. (I don't have a proper engineering formula book at home so I can't look up the compression formula). But once you have the compression in the walls, you divide by the thickness and get the psi force in compression. If it comes out over 1000 psi, (just guessing on compressive strength of clay sphere), there could be an impressive compressive event.
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Post by TDR on Oct 12, 2006 23:26:52 GMT -5
I'm also impressed you were able to reach into that 2400 degree kiln and seal up the sphere.
How airtight is fired pottery as a material? If there was a significant pressure differential between two sides of a pottery barrier, is it not porous enough to pass gas molecules thru it?
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Post by SteveO on Oct 13, 2006 0:17:12 GMT -5
Would it not be measured in Hg?
Is not Vacuum the opposite of compression?
Would not the thickness of the sphere wall be a factor?
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Post by millring on Oct 13, 2006 5:35:23 GMT -5
Thanks for the information and the laughs.
David, I'd go with the second choice. The grammar would be correct even if, as Peter points out, the concept is flawed.
Mike, I'll be going through a stack of shards today in hopes that I can ebay my way to financial security.
Marshall, you just found the lyrics for your next song -- Impressive Compressive Event.
TDR, Stoneware that is vitrified is air-tight. And I never reach into a 2400 degree kiln. I let others do it for me.
SteveO, According to my shop vac, "blowing" is opposite of vacuum.
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Post by Deleted on Oct 13, 2006 9:24:26 GMT -5
God-like potter is correct. The first two words become hyphenated as they are modifying the subject noun, potter, as though they were an adjective. Since there is no compound word godlike in the English language, a hyphen is used to link the two words.
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Post by billhammond on Oct 13, 2006 9:34:02 GMT -5
God-like potter is correct. The first two words become hyphenated as they are modifying the subject noun, potter, as though they were an adjective. Since there is no compound word godlike in the English language, a hyphen is used to link the two words. Well, in deference to my esteemed New York friend, "godlike" appears on page 608 of my trusted Websters New World College Dictionary, Fourth Edition. Which words use hyphens and which do not are determined primarily by frequency of usage. "Childlike," for instance, would be solid. "Goodall-like" would be considered an ersatz construction and thus call for a hyphen. Let your favorite dictionary be your guide. |
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Post by John B on Oct 13, 2006 9:38:25 GMT -5
I assumed the correct version was "god like potter," much like "I like you."
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Post by Deleted on Oct 13, 2006 9:54:05 GMT -5
The answer is 7, DUH!
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