No wonder it is, de facto, a trick question, at the same time Nick maintains 
that he does not intend it to be, or to believe it is, a trick question.  

> On May 29, 2025, at 3:08, Nicholas Thompson <[email protected]> wrote:
> 
> My reasons for doing this is that the distinction between an air temperature 
> that is arrived at by compression and the same air temperature that is 
> arrived at through heating is crucial to meteorology, about which I am trying 
> to write. 

Temperature is a state variable.  That is inherent to its definition, so if the 
word is to mean anything, its meaning is to include that.  If meteorology is a 
discipline within physical science, that is true in meteorology as well as 
anywhere else.  

“State variable” means that its value tells you all it has to tell you about 
its role.  How it was arrived at historically is exactly _not_ distinguishing 
of anything.

Eric 

> 
> On Wed, May 28, 2025 at 8:38 AM Alexander Rasmus <[email protected] 
> <mailto:[email protected]>> wrote:
>> Pieter got all of this, but I’ll pile on. I think Nick is intending us to 
>> think that the initial fill is the same on both sides, but he definitely 
>> hasn’t said this. The answer to the problem as stated is that the barrier 
>> will move left, right, or not at all. I think Nick is intending that the 
>> fill be the same, and that the answer to be that the barrier move to the 
>> right. The pressure in the right cell is lower as the density is lower 
>> (unless the EOS is real weird).
>> 
>> What’s air Nick? You also messed up your corrected version and set the 
>> second initial fill temp to be the post heating temperature 
>> Sent from my iPhone
>> 
>>> On May 28, 2025, at 3:02 AM, Pieter Steenekamp <[email protected] 
>>> <mailto:[email protected]>> wrote:
>>> 
>>> 
>>> I'm not sure if you deliberately left out any mention of the initial 
>>> pressures — perhaps as part of the “catch,” which is common in trick 
>>> questions like this. As I mentioned in my initial answer, it’s common to 
>>> assume the initial pressures are equal, in which case the slider would move 
>>> to the tight.
>>> However, if the twist is that the right-hand cylinder was initially filled 
>>> with high-pressure air, then of course the slider would move to the left.
>>> 
>>> On Wed, 28 May 2025 at 07:14, Nicholas Thompson <[email protected] 
>>> <mailto:[email protected]>> wrote:
>>>> Thanks everybody.   Anybody else?   Remember, please no peeking.  Your 
>>>> efforts have already helped me identify an ambiguity in how I stated the 
>>>> problem.  Here is an edited version.  See if that clarification changes 
>>>> any answers.
>>>> Remember, no peeking before you kick in your answers.  No herding allowed. 
>>>>  
>>>> 
>>>> Side by side, butt-to-butt, two cylinders of air, of equal volume and 
>>>> equal temperature, but different histories. They are separated by a 
>>>> frictionless sliding divider which is now pegged.  Before compression or 
>>>> heating, both started with air at 10 degrees C, and after compression or 
>>>> heating, both arrive at 20 degrees C. The left one has arrived at its 
>>>> present temperature and volume by being compressed, the right-hand one by 
>>>> having its volume set to the same value as the left, BEFORE BEING FILLED 
>>>> WITH AIR AT 20 DEGREES C, and ONLY  then having contents  heated.  All 
>>>> compartments insulated, all manipulations quasi-static.  Now, remove the 
>>>> peg, allowing the partition between the two parts to slide, one way or the 
>>>> other.  Which way would it slide and why. What would your explanation be?  
>>>> Please don't read others' answers until you have submitted your own.  This 
>>>> is enormously helpful to me.  
>>>> 
>>>> On Tue, May 27, 2025 at 10:19 PM Pieter Steenekamp 
>>>> <[email protected] <mailto:[email protected]>> wrote:
>>>>> Assuming the pressures were equal at the start, it will slide from the 
>>>>> left (having been compressed) to the right.
>>>>> From the ideal gas law PV = nRT, both have equal nRT;s so the one with 
>>>>> smaller V must have higher P and it would then push to the right.
>>>>> 
>>>>> On Wed, 28 May 2025 at 04:59, Nicholas Thompson <[email protected] 
>>>>> <mailto:[email protected]>> wrote:
>>>>>> Side by side, butt-to-butt, two cylinders of air, of equal volume and 
>>>>>> equal temperature, but different histories. They are separated by a 
>>>>>> frictionless sliding divider which is now pegged.  Before compression or 
>>>>>> heating, both started with air at 10 degrees C, and after compression or 
>>>>>> heating, both arrive at 20 degrees C. The left one has arrived at its 
>>>>>> present temperature and volume by being compressed, the right-hand one 
>>>>>> by having its volume set to the same value as the left and then having 
>>>>>> contents  heated.  All compartments insulated, all manipulations 
>>>>>> quasi-static.  Now, remove the peg, allowing the partition between the 
>>>>>> two parts to slide, one way or the other.  Which way would it slide and 
>>>>>> why. What would your explanation be?  Please don't read others' answers 
>>>>>> until you have submitted your own.
>>>>>> --
>>>>>> Nicholas S. Thompson
>>>>>> Emeritus Professor of Psychology and Ethology
>>>>>> Clark University
>>>>>> [email protected] 
>>>>>> <mailto:[email protected]>https://wordpress.clarku.edu/nthompson 
>>>>>> <https://linkprotect.cudasvc.com/url?a=https%3a%2f%2fwordpress.clarku.edu%2fnthompson&c=E,1,ziVMqgQPZgRZt2IX9KyStwbNAbv6u78did9vqAD5Uih4uYbBnttqs-1k-EDX73c0ME30LqPyv5hHTRzxTQW39aB7GsOlVgNUP-L72w6_X7TrSBRAT8KwUpP980MU&typo=1>.-
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>>>> 
>>>> 
>>>> 
>>>> --
>>>> Nicholas S. Thompson
>>>> Emeritus Professor of Psychology and Ethology
>>>> Clark University
>>>> [email protected] 
>>>> <mailto:[email protected]>https://wordpress.clarku.edu/nthompson 
>>>> <https://linkprotect.cudasvc.com/url?a=https%3a%2f%2fwordpress.clarku.edu%2fnthompson&c=E,1,ttAkJii414uTDNAR0v9yvtGrdCI40dlpIjgimm6K8_sMObZJPj4sjmYaY3HCUNw8dMwkrVk1wwIXgcpv6dVxvC-djCyIegJT9xbs3bQy&typo=1>.-
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> 
> 
> 
> --
> Nicholas S. Thompson
> Emeritus Professor of Psychology and Ethology
> Clark University
> [email protected] 
> <mailto:[email protected]>https://wordpress.clarku.edu/nthompson 
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