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Homework Help: Zero Magnetic Force

  1. Apr 29, 2009 #1
    1. The problem statement, all variables and given/known data
    A proton with an initial velocity of magnitude v in the +x direction enters a uniform magnetic field. For which direction or directions of the magnetic field, if any, will there be zero magnetic force on the proton?
    + x
    - x
    + y
    - y
    + z
    - z

    2. Relevant equations
    There were no equations i could think of that will help we with this problem, other than the open palm thing that my professor talked about in class today.

    3. The attempt at a solution
    I dont really understand the question. on the graph (+) x is in the third quadrant and thats the velocity. I tried -x by itself, i tried -x, +y, and +z. And +y, +z. All three were incorrect. I dont think i understand what it means to have zero magnetic force on a proton.
  2. jcsd
  3. Apr 29, 2009 #2


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    Homework Helper

    Force on the charged particle is given by F = qvBsin(theta) where theta is the angle between the velocity and the magnetic field.
    Now you can decide when the force is zero.
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