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Homework Help: Predicting Equilibrium?

  1. Oct 26, 2004 #1
    I have this homework question that I an having a lot of trouble with. I am not sure if anyone could help, but here it is:

    Using the definitions of torque and lever arm and the fact that the system is in equilibrium, derive this formula-
    Xo= m1x1 + m2x2 + m3x3
    ....... m1 + m2+ m3

    So, I know all the different formulas for torque and the levers etc... but I can't figure out how to turn them into this formula?
  2. jcsd
  3. Oct 26, 2004 #2


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    Mind telling what [itex]x_0,x_1,x_2,x_3[/itex] are?
    All I can tell is that the equation can be written as such:

    Maybe that helps...
  4. Oct 27, 2004 #3
    That does help, here are some of the given equations in the chapter before the problem:

    T1=m1gl1 T2=m2gl2 l1=Xo-X1 l2=Xo-X2 l3=Xo-X3

    The numbers in the equation:
    Xo= 121.8(.3000) + 71.40(6500) + 145.4(.5005)/ 121.8 + 71.40 + 145.4

    121.8=m1(hanging mass from bar on the left) 71.40=m2(hanging mass on the right)
    145.4=m3(mass from the center of gravity) and we are looking for Xo-the balance point in between m1X1 and m3X3 wih m2X2 on the right of m3X3

    Does that help or make it more confusing?
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