Re: Mass/Energy Conservation

[Doug Craigen <dcc@ESCAPE.CA>]

David Bowman wrote:
> Also, don't forget sweating, tears, & other secretions and the
> evaporation of such; skin cell exfoliations, hair loss, etc., etc.

I did mention sweat (see below).  The others I took to be likely smaller
than the uncertainty in measurements - barring something like a
haircut.  That could be weighed though - shaving is more problematic
because the hair mixes with soap.

> BTW, what's the point of Dave A.'s initial question anyway?
>
> > I assume that you are remembering to include drinking water in the
> > "food" calculation.  There are other mass exchanges as well with
> > sweating and respiration.  We breath out a lot of water vapor (its been
> > -30 here in Winnipeg this week, I've seen that one a lot) plus exchange
> > O2 for CO2.  Hence there is a net loss of weight from breathing.  This
> > might be an interesting back of the envelope calculation.
>
> (Doug, how do you manage to see water *vapor*?  ;-) )

Much as I dislike refering to dictionaries in a physical question...
Funk and Wagnal's Standard College Dictionary:
vapor
-----
1. Moisture in the air; especially visible floating moisture, as light
mist.
2. Any light, cloudy substance in the air, as smoke or fumes.
3. Any substance in the gaseous state, that under ordinary conditions,
is usually a liquid or solid.
4. A gas below its critical temperature

I suspect that you were focussing on definition 3. above, whereas I
generally go with 1.  If I mean gas I say gas, if I mean a light mist I
shorten it to "vapor".



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Doug Craigen
          http://www.dctech.com/physics/about_dc.html