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Homework Help: How do I show the 100N force is cartesian form?

  1. Feb 6, 2007 #1
    1. The problem statement, all variables and given/known data

    See attachment, Im getting everyone of these problems wrong.

    2. Relevant equations

    [tex]M_y = u_y(r_y X F)[/tex]

    Where u=unit vector defining the direction of y axis
    r=distance from y axis to any point on the line of action of F
    F=acting force

    3. The attempt at a solution

    I think im going wrong right from the beginning, how do I show the 100N force is cartesian form? What im doing is :


    AB =\frac{ -0.6i+0.6j+1.2k}{\sqrt{0.6^2+0.6^2+1.2^2}}

    F_{AB} = (100N)\frac{ -0.6i+0.6j+1.2k}{\sqrt{0.6^2+0.6^2+1.2^2}}

    Im not going to bother to post the rest since im pretty sure this isnt how to do this.


    Attached Files:

    • car1.JPG
      File size:
      37.8 KB
    Last edited: Feb 6, 2007
  2. jcsd
  3. Feb 6, 2007 #2
  4. Feb 6, 2007 #3
    Well there's a few ways you can do this. The easiest is to take a moment about the y-axis. You have the force in vector form now, so in your diagram you can redraw that force in the x,y,z direction. Then use the right-hand rule to decide which forces produce moments about the y-axis.
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