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Homework Help: Mobile of Fish in equilibrium

  1. Apr 16, 2010 #1
    1. The problem statement, all variables and given/known data
    The mobile is in equilibrium. The fish B weighs
    27 oz. Determine the weights of fish A, C and D.
    (The weights of the crossbars are negligible).
    1154484.jpg


    2. Relevant equations
    Moment = Force*Distance


    3. The attempt at a solution
    My idea here is to use the moments about each point, solve for one variable. Here is what I have com up with so far, am I on the right track?
    D(14)=A(4) since their moments at that point are in equilibrium.
    B(4)=12(A+D)
    C(24)=6(A+B+D)
    Am I wrong in setting it up this way?
     
  2. jcsd
  3. Apr 16, 2010 #2

    Borek

    User Avatar

    Staff: Mentor

    So far so good.
     
  4. Apr 16, 2010 #3
    So then I just say that I set A=D(14)/4
    Replace A in equation B(4)=12(D+ (D(14)/4))
    Solve for D and then replace D and A values that I get into the equation for
    C(24)=6(B+D+A) solve for C and that is it??? Please tell me that it wasn't that simple?
     
  5. Apr 16, 2010 #4

    Borek

    User Avatar

    Staff: Mentor

    As you wish.

    It wasn't that simple :tongue2:
     
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