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Homework Help: Gr12 Energy Prob

  1. Dec 13, 2008 #1
    1. The problem statement, all variables and given/known data
    "The highest waterfall in Canada is Della Falls in B.C., with a change in elevation of 4.4*10^2m. When the water has fallen 12% of its way to the bottom, its speed is 33 m/s. Neglecting air resistance and fluid friction, determine the speed of the water at the top of the waterfall."

    RTF: V1
    V2 = 33 m/s

    (need help on this part, tell me if I'm doing it right) I pick the ground as a point of reference, so:
    y1 = 4.4*10^2 m
    y2 = (4.4*10^2)(1-0.12)

    2. Relevant equations

    Et1=Et2 (Conservation of Energy)

    3. The attempt at a solution

    1/2mv1^2 + mgy1 = 1/2mv2^2 +mgy2
    (mass cancels out)
    v1 = sqrt( 2 ( 0.5v2^2 + g(y2-y1)))

    I plug everything in and I get 7.4 m/s, book says 5.0 m/s
  2. jcsd
  3. Dec 13, 2008 #2


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    Science Advisor
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    Gold Member

    I get your answer also.
  4. Dec 13, 2008 #3
    guess I'm right then? Thanks
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