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Homework Help: Moments about different points

  1. Oct 7, 2012 #1
    1. The problem statement, all variables and given/known data
    Here is the question along with part of the solution. I am online concerned about finding the force at C.


    3. The attempt at a solution

    For my solution I decided I would sum the moments about point B. However I ended up getting the wrong answer for the force at C. Does anyone know why?
  2. jcsd
  3. Oct 7, 2012 #2


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    You didn't follow the solution manual. You should first check your geometry to see that the angle you denote as 5 degrees is actually 15 degrees. But then if you sum moments about B, C has both vertical and horizontal components, it is not perpendicular to the member.
  4. Oct 7, 2012 #3
    Ah, I reoriented BD so that the angle there is 5 degrees instead of 15 :P. So you are saying force C will not be perpendicular to BD?

    I just summed the moments about B using their answers. I converted the forces C and P so that they are perpendicular to the link BD and summed the moments. The moment does not equal to zero. Is this an error?

    Here is my work:
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