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Energy conservation

  1. Dec 8, 2006 #1
    The maximum speed of a child on a swing is 4.9 m/s. The child’s height above the ground at the lowest point is 0.7 m. How high above the ground is he at his highest point?
    http://img208.imageshack.us/img208/9949/untitledyx0.png [Broken]

    Above is the work done to solve the problem. I don't understand how they went from the blue to the red equation. Wouldn't the two g's cancel out since you would need to divide the left side by mg?
    Last edited by a moderator: May 2, 2017
  2. jcsd
  3. Dec 8, 2006 #2

    Doc Al

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    Staff: Mentor

    You divide all terms by mg. The m's all cancel, since an m appears in all three terms. But g's only cancel in the two terms that had g's--the KE term does not have a g to cancel.
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