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Julius ceasar's last breath .

  1. Feb 19, 2007 #1
    julius ceasar's last breath.....

    hey everyone, hope all is good. not with me, having trouble with a non assessed example in uni, any ideas anyone? :!!)

    1. The problem statement, all variables and given/known data

    make a fully reasoned order of magnitude estimate of the number of molecules from julius ceasar's last breath which were also present in your latest breath.

    2. Relevant equations

    boltzmann equation. pressure equations

    3. The attempt at a solution

    molecules in 1 breath, molecules in world, different pressures at different heights, intergrate pressure.

    pretty stuck here would appreiciate any help!

    cheers all :biggrin:
  2. jcsd
  3. Feb 19, 2007 #2


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    This is an order of magnitude estimate. Keep your model as simple as possible. I would base it only on the the first two numbers in your attempt.
  4. Feb 19, 2007 #3
    do i not need to take into account the change in pressure in the earths atmosphere? simply ratioing the number of molecules in a breath of air to the number in the world seems a bit simple for ten marks?

  5. Feb 19, 2007 #4


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    How are you thinking change in pressure would matter?
  6. Feb 20, 2007 #5
    I had a similar question about king arthurs cup and the water in it and the molecules of it going around in my body etc etc. what you have to do is estimate the volume of air in the earth - forget about the fact that air thins with altitude, just improvise. then just use the fact that most air is nitrogen, so stick with calculating the number of nitrogen molecules in the world. you can look up how much volume on breath of air takes - its about half a litre. Then i'm sure i dont need to tell you the rest? ;) if it works out im guessing there are roughly 10 molecules in your breath of caesers last breath - only a guess though
  7. Feb 20, 2007 #6
    cheers vengeance, got it in the end, final equation something like 10E22/10E22 so 1 molecule, thanks for the advice tho dude
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