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Homework Help: Torque r & F two angles

  1. Nov 12, 2006 #1
    Unless r and F are perpendicular, there are always two angles between their directions that give the same torque for given magnitudes of r and F. Explain why?

    Perhaps I cannot visualize the question, but I cannot see how this can be. As the force moves to the perpendicular position the torque increases. Am I missing something?
  2. jcsd
  3. Nov 12, 2006 #2
    Use the definition of torque. If one angle between the p.v and force vector is theta, what about the other?

    Edit: I guess this holds only for the magnitude of the torque.
    Last edited: Nov 12, 2006
  4. Nov 12, 2006 #3
    [tex] \tau = rF \sin \theta [/tex]

    [tex]sin \theta = \sin (\pi - \theta)[/tex]​

  5. Nov 12, 2006 #4
    I guess I figured that would put the angle outside of between the two angles.
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