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Homework Help: Need help equilibrium physics

  1. Nov 6, 2007 #1
    a 65 kg sign hung centered from a uniform rod of mass 9.8 kg and length 2.3 m. At one end(left) the rod is attached to the wall by a pivot; at the other end(right) it's supported by a cable that can withstand a maximum tension of 760 N. What is the minimum height h above the pivot for anchoring the cable to the wall?


    i need help on setting up an equation to solve...
    what i have so far i dont know how wrong or right it is.

    (Force of sign)(Radius of sign)+(Force of rod)(Radius of rod)-(Tension)=0
    (637N)(1.15m)+(96.04N)(1.15m)-m*g*sin(angle away from wall)=0

    ??? i dont really know exactly where im going with this
  2. jcsd
  3. Nov 6, 2007 #2


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    Homework Helper

    you need the torque about that point to be zero... so you need:

    (Force of sign)(Radius of sign)+(Force of rod)(Radius of rod)-(vertical component of Tension)*distance=0

    (since horizontal component of tension exerts 0 torque about the pivot)

    what is the vertical component of Tension in terms of the total tension T... what is the distance here?
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