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Thread: [SOLVED] Need help with one thing

  1. #1
    Sep 2008

    [SOLVED] Need help with one thing

    i dont know what to do with the number 3.2 in this problem trying to obtian the loudness of a sound in decibals. I already did some of the steps

    $\displaystyle 10log(3.2* 10^{-5}W/m^{2}-10^{-12}W/m^{2})$ I just dont know what to do with the 3.2 in the equation. Only have done problems that use $\displaystyle 1.0* 10^{n}$ And with 1.0 the answer would be $\displaystyle 10^{7}$ or 70 dB
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  2. #2
    MHF Contributor
    Aug 2007
    $\displaystyle 3.2\cdot 10^{-5}\;-\;1.0\cdot 10^{-12}$

    $\displaystyle \;=\;32000000\cdot 10^{-12}\;-\;1.0\cdot 10^{-12}$

    $\displaystyle \;=\;31999999\cdot 10^{-12}$

    Where does that leave us?

    Of course, someone is going to worry about significant digits. Subtracting with 7 orders of magnitude difference is a touchy subject. With a few more orders of magnitude, I like this explanation:

    Weight of the Earth + Grain of Sand = Weight of the Earth
    Last edited by TKHunny; Feb 4th 2010 at 07:01 PM.
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