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Need confirmation- Energy and PEgrav

  1. Oct 7, 2005 #1
    The energy content of beer is about 1.8e6 J/kg. If that energy could be turned completely into gravitational PE, how much beer would we need to raise a 0.9 kg mass 1.5 km into the air?

    What i did for this, was just used the equation PEgrav=mg*delta H.

    so .9kg*9.81m/s^2*1500m =13243.5 kgm^2/s^2.

    So i set that =1.8e6J/kg, and divided 13243.5 by 1.8e6, giving me .0073575kg.

    So, i need 7.3575 grams of beer correct?

    It just seems really low to me so just looking for confirmation.

    Thanks
     
  2. jcsd
  3. Oct 7, 2005 #2

    mezarashi

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    Homework Helper

    Not at all. You need 13243.5 Joules of energy, and there is what? 18000000 Joules per kilogram in beer? Looking at the numbers side by side

    13243.5 - Needed
    1800000 - Provided per kg
    1800.0 - Provided per gram
    ======================
     
  4. Oct 7, 2005 #3
    oh alright, thanks :D

    I was right, just hadn't thought about it like that.
     
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