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Homework Help: Physics 3-D Force Vector Question

  1. Sep 22, 2013 #1
    The problem statement, all variables and given/known data

    Determine the magnitude of the projected component of F1 along the line of action of F2, if the cables each exert a force of 410 N on the post.


    The attempt at a solution

    I know how to figure out F2x, F2y, and F2z, but I have no idea how to find F1y and F1x. Also, what does it mean by "F1 along the line of action of F2" and how would I give a final answer in that format?

    Thank you
  2. jcsd
  3. Sep 22, 2013 #2
    For F1x and F1y , first calculate the projection on the given line in between x and -y >> G = F1 cos(90-35) then
    F1x = G cos(20) and F1y = G cos(90+20) .
    For F1 in the direction of F2 just take the dot product... (F1.F2)/ |F2|.

    seems right to me, but please check with the angles and all...
  4. Sep 22, 2013 #3

    Simon Bridge

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    Science Advisor
    Homework Helper

    Pretend that F2 is an axis - F1 has a component parallel to F2 and another one perpendicular to it.

    Hint: what do dot and cross products do?

    Note: debsankar has attempted to all-but do the problem for you - something that is usually unhelpful in the long-term. You should attempt to understand the approach used as well as applying it.
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