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Homework Help: Torque Question

  1. Jan 14, 2008 #1
    [SOLVED] Torque Question

    1. The problem statement, all variables and given/known data

    See diagram for problem

    additional instructions
    For each of the three forces shown, compute the moment (N m, + CCW) about point A. Assume 3 SF for all numbers.

    I am trying to solve for the moment(torque) of F3

    2. Relevant equations

    Force * (Distance between force and point A) * sine(theta)??

    3. The attempt at a solution

    too many to name.

    Attached Files:

  2. jcsd
  3. Jan 15, 2008 #2

    That's it! Problem over right there. Tounet = F.r.sinX. Add the torques seperately, one by one.
  4. Jan 15, 2008 #3
    For force 3, the r value is supposed to be the direct line between it and the point of pivot right? Do I use the hypotenuse of the triangle for the r value? Also what angle do I use (arctan (3 / 4)??), and am I supposed to somehow break up the force into x and y components? I've tried some of this stuff, but none of it seemed to work. Thanks for your time.
    Last edited: Jan 15, 2008
  5. Jan 15, 2008 #4

    Doc Al

    User Avatar

    Staff: Mentor

    When using [itex]r F \sin\theta[/itex], the angle is the angle between the position vector and the force vector.
    You can always break a force into its components and then find the torque for each component and add them. (That would be much quicker, especially if you realize that [itex]r \sin\theta[/itex] is the perpendicular distance to the line of the force.)
  6. Jan 15, 2008 #5
    Thanks guys.
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