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Energy Up A Mountain!

  1. Oct 2, 2012 #1
    1. The problem statement, all variables and given/known data
    What is the energy needed to take a 1,112 kg car to 1.2 km up a mountain? Write your answer to 3 significant figures.

    2. Relevant equations
    PE = KE
    PE = mgh
    KE = ½mv2
    mgh = ½mv2
    1 km = 1000 m

    3. The attempt at a solution
    h = 1.2 km = 1200 m
    PE = mgh = (1112)(9.8)(1200) = 13077120
    PE = KE
    Energy = 13077120 Joules

    I don't think my answer is correct because it says to write my answer to 3 significant figures.
    Where did I go wrong???
  2. jcsd
  3. Oct 2, 2012 #2
    dont forget...when dealing with large numbers its best to include as many sig figs in your calculations as possible, use 9.81 instead of 9.8 and you will get something that you can round to 1.31E7 J
  4. Oct 2, 2012 #3
    (1112)(9.81)(1200) = 13090464
    13090464 = 1.31E7

    Energy = 1.31E7 Joules

    So, is that the answer?
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