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Determine the electron's velocity.

  1. Aug 6, 2011 #1
    1. The problem statement, all variables and given/known data
    An electron experiences a force F = (3.4i - 1.9j)x10^-13 N when passing through a magnetic field B = (0.50 T)k Determine the electron's velocity.
    v(x) =
    v(y) =

    2. Relevant equations
    v = F/qB

    3. The attempt at a solution
    v = (3.4i - 1.9j)x10^-13 / (1.6x10^-19)(0.50)k = (4.25i - 2.375j)x10^6
    v(x) = 4.25x10^6
    v(y) = -2.375x10^6

    I know I'm doing something wrong, I'm just not sure what. Please help.
  2. jcsd
  3. Aug 6, 2011 #2


    User Avatar

    Staff: Mentor

    Consider that you're dealing with a vector equation. [itex] F = q(v \times B)[/itex]

    Your magnetic field vector, B, has only a single component (the k component), so the cross product with the velocity vector will be pretty simple. If you assume that the velocity vector has components vi, vj, vk, what is the cross product?

    Multiply the cross product components by the charge and equate the corresponding force components.
  4. Aug 6, 2011 #3
    thanks, I was able to figure it out.

    v(x) = -2.4x10^6 m/s
    v(y) = -4.3x10^6 m/s
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