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Homework Help: Torque direction for any system of particles

  1. Nov 14, 2011 #1
    1. The problem statement, all variables and given/known data

    A particle is to move in an xy plane, clockwise around the origin as seen from the positive side of the z axis. In unit-vector notation, what torque acts on the particle at time t = 9.5 s if the magnitude of its angular momentum about the origin is (a) 8.0 kg·m2/s, (b) 8.0t^2 kg·m2/s3, (c) 8.0t^(1/2) kg·m2/s3/2, and (d) 8.0/t^2 kg·m2*s?

    2. Relevant equations


    3. The attempt at a solution

    All i have to do is take the time derivative of the given angular momentum and plug in t. I can get the magnitude of the torque with the equation but i do not know how to get the direction of torque. Please explain! Thanks
  2. jcsd
  3. Nov 14, 2011 #2
    Look up the right hand rule :)
  4. Nov 14, 2011 #3
    Well, i'm not too sure how to apply right hand rule with dl/dt, perhaps you can give me some insight?
  5. Nov 14, 2011 #4
    Wait, do i just move my fingers to the direction its turning, in this case clockwise? If so then its -k, right?
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