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Hanging Sign, Tension

  1. Dec 13, 2011 #1
    A purple beam is hinged to a wall to hold up a blue sign. The beam has a mass of mb = 6.2 kg and the sign has a mass of ms = 15.1 kg. The length of the beam is L = 2.78 m. The sign is attached at the very end of the beam, but the horizontal wire holding up the beam is attached 2/3 of the way to the end of the beam. The angle the wire makes with the beam is θ = 30.6°.

    What is the tension in the wire?

    I have set the torques of the beam's weight and the sign's weight equal to the tension torque as follows:
    (6.2)(9.8)(.5)(2.78)(cos30.6) + (15.1)(9.8)(2.78)(cos30.6) = (T/sin30.6)(2/3)(2.78)

    Solving for T, I keep getting 117 N which is not the right answer...
    Could anyone explain where I am going wrong?

    Attached Files:

    Last edited: Dec 13, 2011
  2. jcsd
  3. Dec 13, 2011 #2
    Replace '/' by 'times'
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