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Simple Machines Proble,

  1. Jan 6, 2008 #1
    [SOLVED] Simple Machines Proble,

    1. The problem statement, all variables and given/known data
    Two kids are riding on a seesaw that is 3.0m long with its fulcrum exactly in the middle. When one end touches the ground, the other end is 1.4m in the air. If one child has a mass of 20.0kg and the other is 28.0kg, which child sits at the end of the seesaw and how far in does the other child sit so they can ride the seesaw effectively? Assume 100% efficiency for the seesaw.

    2. Relevant equations [I'm not sure if all these are needed, but these are the equations we were given in this unit]
    Wi = Fi x Di
    Wo = Fo x Do
    MA = Fo / Fi
    IMA = Di / Do
    %eff = Wo / Wi or MA / IMA

    3. The attempt at a solution
    Umm I know from class that the answer is x = 2.14 m , but I don't know how to get there.
    The stuff I attempted is majorly messed. I know it's wrong but I have no clue what to do. I basically found the Di and Do for each kid and subtracted them or something. I'm not even sure anymore. Lol..
  2. jcsd
  3. Jan 6, 2008 #2

    Shooting Star

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    When is the seesaw ridden effectively? Is that related to total moment about the fulcrum in any way?
  4. Jan 6, 2008 #3
    When Fo is greater than Fi?
    That might be it.

    *edit* JUST KIDDING! It's actually that Wo has to be equal to Wi.
    Last edited: Jan 6, 2008
  5. Jan 7, 2008 #4

    Shooting Star

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    Right, but have you understood?
  6. Jan 7, 2008 #5
    Lol, I guess I do now that I figured that out. Nevermind!!
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