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Homework Help: Finding 3D component vectors

  1. Aug 24, 2011 #1
    Express each force as a Cartesian vector and then determine the resultant force F. Find the magnitude and coordinate direction angles of the resultant force and sketch this vector on th coordinate system.
    There's a drawing of 1 force(F2) of magnitude 130N, along the negative z direction(-z), and another force(F1) of magnitude 80N, 40 degrees from the +x direction, 50 degrees from the -y direction and an incline of 30 degrees on the +z direction.

    I want to know the component vectors of this force

    I know how to find the component vectors of the forces using the x-axis direction and the y-axis directions only, I don't know the way to find the component vectors for the z-axis. (Which I think are (80sin40i and 80cos40j) if I am wrong please correct me.)
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Aug 24, 2011 #2


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    Hi yuhumei and welcome to PF. Consider a plane defined by the z-axis and the vector. Draw your vector assuming that the paper is that plane. Can you find its z-component?
  4. Aug 24, 2011 #3


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    you're mis-interpreting the diagram ...
    If those angles were really from the vector itself straight to each axis,
    then (cos^2 + cos^2 + cos^2) has to = 1.
    Probably, the "projection" of the 80N force onto the xy plane is 50deg from -y and 40deg from +x ... and the vector is 30deg from z .
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