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A tire with lots of air!


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4 replies to this topic

#1 Martini

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Posted 04 August 2007 - 05:39 AM

If you're the type to complain that a riddle requires outside information, don't bother reading this.


In general, if you have air in a container and you double that amount of air, the pressure will become double the old pressure. This is true of all gases. Well, this isn't exactly true, but for the purposes of this riddle, it is close enough.

So here's the question: If you have an automobile tire filled with the typical 32 psi and you double the amount of air molecules in it, what pressure will a tire gauge now read? Assume that this is a tire that doesn't expand.
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#2 jpaterson3

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Posted 04 August 2007 - 08:04 AM

atmosperic pressure = 14.6960 psi
so in the tire there is truly (32 + 14.7) psi or 46.7 psi
now double that and real pressure in the tire is 93.4 psi
take away that 1 atmosphere of pressure and the gauge will read 78.7 psi
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#3 imtcb

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Posted 06 August 2007 - 07:14 PM

0psi (the tire would have exploded, so the pressure would be the same as regular air...)
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#4 Martini

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Posted 06 August 2007 - 07:34 PM

0psi (the tire would have exploded, so the pressure would be the same as regular air...)


No. Tires are very strong and can handle being filled with much more air than is recommended. Tires are frequently filled to almost double its recommendation to check for leaks. There is no guarantee that a tire with double its recommended air pressure won't explode (especially if left that way for an extended period of time and driven on), but you can't expect that this will necessarily happen immediately. Also, one of the conditions of the riddle is, "this is a tire that doesn't expand". You are also incorrect that "regular air" is 0 psi. jpaterson3 posted the correct answer.
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#5 imtcb

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Posted 06 August 2007 - 11:32 PM

No. Tires are very strong and can handle being filled with much more air than is recommended. Tires are frequently filled to almost double its recommendation to check for leaks. There is no guarantee that a tire with double its recommended air pressure won't explode (especially if left that way for an extended period of time and driven on), but you can't expect that this will necessarily happen immediately. Also, one of the conditions of the riddle is, "this is a tire that doesn't expand". You are also incorrect that "regular air" is 0 psi. jpaterson3 posted the correct answer.


Ah, but the reason tires are so strong is that they DO expand to allowed added pressure. But really I was joking around. I knew it had to do with tire gauges starting at 0psi and really meaning 0psi over atmosphere. (which, by the way, changes with altitude.)
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