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Homework Help: Moment about an axis - need help please

  1. Jan 25, 2014 #1
    (Figure is attached) Find the tension in the cable AB such that the net moment about the hinge axis CD induced by the forces F and P is zero. The force F is applied at point A and the force P is applied at point E. The magnitude of the force P is P = 65 lb. Two coordinate direction angles for the force P are known: beta = 37 degrees and gamma = 165 degrees. The hinged plate is rectangular.

    - I found the unit vector CD {0i + 0.8j + 0.6k}
    - I know that the force vector will be F(ab){-0.43i + 0.29j + 0.86k}

    How do I find the third coordinate direction angle for the force P?
    From there, what radius do I use for my cross product? I can pick any point on the line of action CD, correct?

    Attached Files:

  2. jcsd
  3. Jan 25, 2014 #2


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    Staff: Mentor

    What is the definition of ##\beta## and ##\gamma##?
    They are related to the direction of P somehow.

    The one closest to the point where P acts.
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