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Torque with sign attached to a rod

  1. May 6, 2013 #1
    1. The problem statement, all variables and given/known data
    a 54.8 kg uniform square sign, 2.00 m on a side, is hung from a 3.00 m rod of negligible mass. A cable is attached to the end of the rod and to a point on the wall 4.00 m above the point where the rod is fixed to the wall.
    6Apo0YU.png

    2. Relevant equations



    3. The attempt at a solution
    Ʃτ=Trsin(θ1) -mg(r)(sin(θ2))=0
    cable length=sqrt(4^2 +3^2)=5
    r=3
    arctan(4/3)=51.3*=θ1
    180-(51.3+90)=36.86=θ2
    T(3)(sin(53.1)-(54.6)(9.8)(3)sin(90)=0
    T=1605/2.389=669N

    That's wrong...what am I forgetting to do?
     
  2. jcsd
  3. May 6, 2013 #2

    SammyS

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    What is it you're trying to find ?
     

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  4. May 7, 2013 #3

    haruspex

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    How far from the wall is the centre of mass of the sign (which weighs 54.8kg, not 54.6)?
     
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