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Homework Help: Magnetic Force

  1. Jun 27, 2007 #1
    1. The problem statement, all variables and given/known data

    An electron has a velocity of 1.20 x 10^4 m/s in the +x direction. An acceleration of 2.00 x 10^12 m/s/s in the +z dir in a uniform electric and magnetic field. The electric field is 20.0 N/C in the +z direction. What can you determine about the magnetic field? What can you not determine?

    2. Relevant equations

    F = q(v x B)
    e = -1.67 x 10^-19 C
    3. The attempt at a solution

    I can see why the mag. field would be Bz = 0 and By = something.
    But I'm not sure how to find the value of By or why it will have a possible value to Bx.

    I can find the electric force, but I don't know how I could relate that to magnetic force. F = Eq.

    I also don't really know how to use the acceleration, it seems that the acceleration would only be useful if I needed to use the gravitational force... (I can't say the magnetic force is equal to mass*acceleration can I?)
     
  2. jcsd
  3. Jun 27, 2007 #2

    Doc Al

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    Staff: Mentor

    The acceleration allows you to determine the net force on the electron.
     
  4. Jun 27, 2007 #3
    Is using Net force = Eq + qvxB on the right track?
     
  5. Jun 27, 2007 #4

    Doc Al

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    Staff: Mentor

    Yes, something like that. (I presume you can ignore gravity.)
     
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