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Pivot Points and Hanging Signs

  1. Mar 31, 2009 #1
    1. The problem statement, all variables and given/known data
    A 66 kg sign hung centered from a uniform rod of mass 8.2kg and length 2.3m. At one end the rod is attached to the wall by a pivot; at the other end it's supported by a cable that can withstand a maximum tension of 800 N. what is the minimum height h above the pivot for anchoring the cable to the wall?



    2. Relevant equations

    Not entirely sure if these apply.

    [tex]\tau[/tex] = r x F
    [tex]\tau[/tex] = [tex]\Sigma[/tex]

    3. The attempt at a solution

    Mg = (74.2)(9.8) = 727.16 N (Total Fy)

    [tex]\tau[/tex] = (2.3)*(727.16) = 1672.5

    After I get this information I'm lost.
     
  2. jcsd
  3. Apr 1, 2009 #2

    tiny-tim

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    Welcome to PF!

    Hi SpeedPhysics ! Welcome to PF! :smile:
    (it's not 2.3 … the weight goes through the centre :wink:)

    ok, that's the torque (the moment) of the weight …

    now, if you call the tension T, what's the torque of the tension? :smile:
     
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