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Homework Help: Static Equilibrium

  1. Oct 28, 2009 #1
    1. The problem statement, all variables and given/known data
    In the figure below, a uniform beam of weight 520 N and length 3.4 m is suspended horizontally. On the left it is hinged to a wall; on the right is it supported by a cable bolted to the wall at distance D above the beam. The least tension that will snap the cable is 1200 N.

    What value of D corresponds to that tension?

    2. Relevant equations

    [tex]\Sigma[/tex]F in the x direction = 1200

    3. The attempt at a solution
    That equation is a guess within itself..I really have no clue how I should go about solving this problem..
  2. jcsd
  3. Oct 29, 2009 #2


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    Homework Helper

    The beam is in static equilibrium; it's not moving and not accelerating. Because of that, the sum of the forces be in the x and y directions must be 0.

    That said, I don't think using forces is the best way to approach this problem. Try using torque: because the beam is not rotating, torque must be zero about any reference frame.
  4. Oct 29, 2009 #3
    Oh ok so I would set it up like this,

    [tex]\Sigma\tau[/tex] = 3.0meters(mg) + ???

    The question marks meaning that I don't know what to put after that first 3meters multiplied by mass times gravity.

    Thank you for your help!
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