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A kind of Fermi Questions

  1. Dec 2, 2012 #1
    1. How many sands on the earth?



    2. Hints: Using the Fermi estimation



    3.
     
  2. jcsd
  3. Dec 2, 2012 #2

    mfb

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    What did you do so far? Where did you run into problems?
    What is "sands"? Do you mean grains of sand?
     
  4. Dec 2, 2012 #3
    Yes, I mean the "grains of sand"

    I do not really understand your first two questions.
     
  5. Dec 2, 2012 #4

    mfb

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    From the board rules:
    This is not a board where others do your homework. We can help you if you run into problems, but it is your homework.
     
  6. Dec 2, 2012 #5
    Oh,yes. When I first saw this question, I have no idea about that. However, now I know that this question is a kind of Fermi questions, which need appropriate estimation.

    But the problem is that I do not know how to start. There is another Fermi question, " How many Piano Tuners in New York? " , I can do that by using the estimation of the population of NY, the amount of pianos, the working time of Tuners, etc.

    However, when I am asked for "How many grains of sand? ", I don't know what data should I use to estimate
     
  7. Dec 2, 2012 #6

    haruspex

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    One way to approach it is to think about what parameters, if changed, would radically change your answer. E.g. if all the sand grains were a million times smaller than they actually are, that would make a lot more of them. Would this alter any other information available to you? If not, having an estimate for average grain size will be essential.
     
  8. Dec 2, 2012 #7
    I found this short book on order of magnitude estimation rather helpful

    Link
     
  9. Dec 2, 2012 #8
    Thank you very much, thats very helpful
     
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