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Homework Help: Boom Supported by a Cable

  1. Nov 8, 2009 #1
    1. The problem statement, all variables and given/known data

    A sign is supported by a uniform horizontal boom of length 3.00 m and weight 80.0 N. A cable, inclined at an angle of 35 with the boom, is attached at a distance of 2.38 m from the hinge in the wall (see figure below). The weight of the sign is 120 N. What is the tension in the cable and what are the horizontal and vertical forces Fx and Fy exerted on the boom by the hinge?

    2. Relevant equations

    I had 3 equations:
    fx =Tcos 35
    fy = 180+120-Tsin 35
    Torque = Tsin 35 (2.38)-200(1.5)
    solved for torque n got ....17.826...which is far from accurate! PLEASE HELP!!

    3. The attempt at a solution
    Im sooooooo lost...pic attached!

    Attached Files:

    Last edited: Nov 8, 2009
  2. jcsd
  3. Nov 8, 2009 #2


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    Science Advisor
    Homework Helper

    Hi agadag! :smile:

    (your fy should start 80, but I expect that's a typo?)

    Your 200(1.5) is wrong …

    you must find the moments (torques) of each weight separately. :wink:
  4. Nov 8, 2009 #3
    yup that was a typo.
    sooo what ur saying is..in order to find Torque:
    Torque = Tsin 35(2.38) - [80(1.5) + 120(3)]
    480 = T sin 35(2.38)
    T = 350!
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