>>> Estimate the mass of air in this room.
>>
>> 3 grams?
> 
> Estimate, not guess!

Well, with no actual data to estimate with, it's kinda hard. :-P

> You'll never make an Engineer if you can't tell 
> when your calculations are off by several orders of magnitude.

Heh. Well, I have no idea what the volume of this room is. I don't even 
"really" know how big a meter is. It used to be the length of my arms, 
but they're a tad bigger now. ;-)

> BTW a 
> cubic metre of air is about 1kg, so you must be in a very small room.

Really? I was under the impression that all gasses are absurdly light. 
(E.g., off the top of my head Oxygen is supposed to be something silly 
like 0.000004 g per cubic meter or something.)

> I think it's safe to assume the external temperature is lower than the 
> internals of the bird, but anyway the point of this one was that for 
> cylinders below a certain radius lagging them actually makes them 
> release more heat rather than less, because the surface area increase 
> has more affect than the lagging.  Useful to know if you ever think 
> about insulating thin pipes :-)

Now, see, I was under the impression that lagging traps air, and hence 
the "effective" surface area would still be the same.

>> ...oh, wait, maybe you meant the *graph* of this?
> 
> Har har.

Aww, c'mon! I thought that was a really neat drawing! :-D

>> Hmm. Well two cubed is 8, while three squared is 9, so I'm going to go 
>> with pi^e being larger.
> 
> Wrong!
> 
>> Presumably "proving" this would simply involve slightly more 
>> arithmetic. :-P
> 
> http://mathforum.org/library/drmath/view/53916.html

...OK, I am now completely bemused. Apparently e^3 is roughly 20. I 
cannot work out how that can possibly be. 2^3 is clearly 8. My head 
hurts just thinking about it.

As an aside, I notice the difference turns out to be especially tiny. :-P

>> I don't know why it took me so long; it's really quite 
>> simple when you look at it. I think I just confused myself too much to 
>> see it...
> 
> That was the story of my whole thermodynamics course at university!

I think you need... THERMITE!! 8^D

Post a reply to this message