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Finding Angles of Interacting Forces

  1. Apr 6, 2013 #1
    1. The problem statement, all variables and given/known data

    http://grab.by/lp4S

    This probably shouldn't be too hard, but I'm getting pretty stuck. On the attached picture, the angles 67.4 and 22.6 are given, but I am not sure how they were found. Taking all the given information on the picture (besides those two angles), how would I find them? I think my trig is just rusty and there's probably an easy solution.


    2. Relevant equations



    3. The attempt at a solution

    I tried to create a force triangle and use the law of cosines and to get F(BD), but that didn't work out, and I'm sort of stuck otherwise. Any help would be greatly appreciated. Thanks!
     
  2. jcsd
  3. Apr 6, 2013 #2

    haruspex

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    From the picture, it seems you would have three unknowns: the magnitudes of forces FBC and FBD, and the direction of FBD. Resolving in two axes will only give you two equations, so there's not enough information to deduce the angle.
    Where it says "since the direction of FBD is not clear", I think it only means the sense is unclear - i.e. is it positive or negative in the direction shown? For the purposes of solving the problem, just assume a particular sense and see what sign you get from the solution.
     
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