Re: Coupled Elevators?

[John Mallinckrodt <ajmallinckro@CSUPOMONA.EDU>]

Michael,

The reason I chose the elevator example is precisely *because*
elevators do not work that way.  I wanted an example in which one
system lost energy at the same rate as an adjacent (or at least
nearby) system gained energy, but for which there was obviously no
causal connection between the two energy changes.

My example was initially attacked on the basis that the two
elevators are not physically contiguous which was beside my main
point.  I believe that it was in that *response* that the
suggestion that elevators were coupled arose.

Interestingly enough, if elevators *did* work that way, I think I
might be willing to say that energy *does* flow from one system to
the other *despite* the fact that the two systems are not
physically contiguous.

John

On Wed, 19 Sep 2001, Michael Edmiston wrote:

> In the "energy" exchange on this list, there has been a reference to one
> elevator gaining energy while another elevator is losing energy.  I don't
> have statistics to support this, but I would guess over 99% of elevators do
> not work this way.
>
> Cable elevators have counterweights.  If two elevators served as the
> counterweights for each other, they would have to run coupled... each
> stopping when the other stopped.  Have you ever been in an elevator that
> works this way?  You're on the 40th floor, you press the lobby button, no
> other buttons are pressed, yet you stop at the 34th, 28th, 23rd, 15th, 8th
> floors because someone was getting out on those floors from the other
> elevator going up?  I never have been.  The only coupled elevators I am
> aware of are those serving two fixed locations and operated by an attendant.
> I think I was told that the elevator into Carlsbad Caverns works this way;
> one group of people goes down at the same time another group comes up.  But
> in general, elevators do not work this way.
>
> Also, for short buildings (2 to 5 floors) the elevator is often hydraulic
> and doesn't have a cable or counterweight.
>
> I know this is nitpicking, but this is not the only time I have seen this
> description used (one elevator gaining energy while a coupled one loses
> energy).  It seems to me we ought to keep our examples more true to life.
> It would be easy to fix this by talking about the energy gain/loss of the
> "counterweight."

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