[long] Re: Legal traps in open source

[David Gibson]

On Thu, Oct 31, 2002 at 01:45:52PM +1100, Daniel Smith wrote:
> > 
> > Maybe I'm doing something wrong with my maths here - they were serving 
> > the coffee at 180F, which comes to:
> > 
> >   (180F - 32F) * (5C/9F) = 82C
> > 
> > By my measurement, water in Canberra boils at about 97C, meaning that my 
> > tea/coffee will usually be served at least as hot as McDonald's hot 
> > beverages ever were - I don't know how to adjust for adding cold powder 
> > (for instant coffee) and sugar.
> 
> More to the point, the water is ~97C when it comes out of the kettle.
> As soon as it hits your ceramic cup (at ~25C) it will *rapidly* cool and
> hit an equilibrium of 50-70C. Depending on cup size, mass and materials. 
> Probably within 10-15 seconds.

I'm not sure this seems implausible.  Water has a very high specific
heat and a pretty high density, so its thermal mass is *much* larger
than that of a ceramic mug.  Admittedly, the temperature differential
is largish (~75K) , so certainly it will drop a certain amount fairly
quickly.  But does it really drop this far, this fast - especially
given that ceramic is a poor conductor of heat, I'd be surprised if
equlibrium was established that fast.

80-90C seems reasonably plausible within 15s, but I'd have to see
figures to be convinced of 50-70 (though I'd expect that in 5-10
minutes).

-- 
David Gibson			| For every complex problem there is a
david at gibson.dropbear.id.au	| solution which is simple, neat and
				| wrong.
http://www.ozlabs.org/people/dgibson