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Homework Help: Lorentz Force and Coulomb Force

  1. Mar 25, 2009 #1
    1. The problem statement, all variables and given/known data

    In frame S, two identical point charges q move abreast along lines parallel to the x-axis, a distance r apart and with speed v. Determine the force in S that each exerts on the other:

    a) using the lorentz force in conjunction with the field of a moving charged particle
    b) by transforming the Coulomb force from the particle's rest frame to the frame S

    2. Relevant equations
    F = q(e + (U X B)/C)
    F = ke(q1q2/r^2)

    3. The attempt at a solution

    For a) I am not sure how to incorporate r into the equation (i assume that u and v are the same for this problem...meaning I can use v in the equation instead of u. I think it has to do with the field of a moving charged particle, but I can't see how that relates in a way that I can use.

    For b) I am not sure how that could be transformed. I know how to transform E and B using the covarient and Contravarient forms. And I dont see how the speed would fit into that...does it go back to the basic lorentz factor, that has v in it.
  2. jcsd
  3. Mar 25, 2009 #2
    okay I think I figured out the second one. It is a lot simpler than I was thinking. But 1, I still have no idea. My teacher's hint was use www.physics.gmu.edu/~joe/PHYS428[/URL] topic 6 slide 15. But I do not see how that would work out...
    Last edited by a moderator: Apr 24, 2017
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