Re: [asa] ideal systems & approximations (was writing equations - a request)

So as long as you evacuated all gases from the enclosure, had perfect
reflective surface (no pesky doors or windows to interfere with perfect
reflection) and had two black-body irons with an initial amount of heat,
and were willing to concede that they were useless except to dispense
that initial amount of heat, then the system could stay that way
infinitely, couldn't it?

We science teachers like to train students toward skepticism regarding
claims of perpetual motion machines, but wouldn't a spinning flywheel in
the vacuum of space qualify as one? As long as no energy is taken from
it, it spins forever (so no violation of first law). But then again,
this doesn't involve any energy conversion from one form to another so
the second law never comes into play, and it really wouldn't be a
"machine" I guess. But it would be perpetual motion -- a kinetic analog
to your perfect radiation system.

--merv

Bill Hamilton wrote:

>I _still_ say that energy from the irons is absorbed by the clothes being
>ironed and therefore not available for heating thee other iron. In addition,
>the iron must rest on an ironing board, which would prevent some of the
>radiation from reaching the ellipsoid.
>
>--- George Murphy <gmurphy@raex.com> wrote:
>
>
>
>>With perfect reflectors &c - again this is an ideal Gedankenexperiment - all
>>the rays emitted by the iron should go to the other focus.
>>
>>But ray optics is only an approximation.
>>
>>Shalom
>>George
>>http://web.raex.com/~gmurphy/
>>----- Original Message -----
>>From: "Bill Hamilton" <williamehamiltonjr@yahoo.com>
>>To: "George Murphy" <gmurphy@raex.com>; "ASA list" <asa@calvin.edu>; "Janice
>>Matchett" <janmatch@earthlink.net>
>>Sent: Thursday, July 20, 2006 3:09 PM
>>Subject: Re: [asa] writing equations - a request
>>
>>
>>
>>
>>>What about
>>> the heat energy that is disipated from the iron into the clothes
>>> the heat energy that is absorbed by the air between the two irons
>>> the heat energy that is absorbed by objects in the room (including the
>>>person doing the ironing)
>>>???
>>>
>>>--- George Murphy <gmurphy@raex.com> wrote:
>>>
>>>
>>>
>>>>Sort of, but the connection is pretty remote.
>>>>
>>>>The thrifty owners of the laundry have constructed their building in the
>>>>form
>>>>of an ellipsoid, and put irons at both foci. All the radiation from an
>>>>instrument at one focus as it irons clothes is reflected to the other
>>>>focus
>>>>(by a well known property of the ellipse) & heats the other iron, which
>>>>can
>>>>then be used to iron other clothes. No heat is lost & no money needs to
>>>>be
>>>>spent in heating the irons once they've been heated up initially.
>>>>
>>>>What's wrong with this picture?
>>>>
>>>>(Of course an iron - whether a "mangle" or the usual household variety -
>>>>isn't a mathematical point but that's not the "point" here.)
>>>>
>>>>Shalom
>>>>George
>>>>http://web.raex.com/~gmurphy/
>>>> ----- Original Message -----
>>>> From: Janice Matchett
>>>> To: George Murphy ; ASA list
>>>> Sent: Thursday, July 20, 2006 12:17 PM
>>>> Subject: Re: [asa] writing equations - a request
>>>>
>>>>
>>>> At 11:27 AM 7/20/2006, George Murphy wrote:
>>>>
>>>>
>>>> A teaser: How many know "The paradox of the Chinese laundry"?
>>>>
>>>>
>>>> @ Physicists know that we don't live in a frictionless world, so does
>>>>it
>>>>have anything to do with a lack of friction?
>>>>
>>>> ~ Janice
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>Bill Hamilton
>>>William E. Hamilton, Jr., Ph.D.
>>>248.652.4148 (home) 248.821.8156 (mobile)
>>>"...If God is for us, who is against us?" Rom 8:31
>>>
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>>
>>
>
>
>Bill Hamilton
>William E. Hamilton, Jr., Ph.D.
>248.652.4148 (home) 248.821.8156 (mobile)
>"...If God is for us, who is against us?" Rom 8:31
>
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>
>
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>

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Received on Thu Jul 20 22:59:37 2006