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Homework Help: Velocity Selector

  1. Oct 19, 2007 #1
    1. The problem statement, all variables and given/known data

    A proton enters a space in which there are both electric and magnetic fields. The electric field points vertically upward and the strength is 1.30×105 V/m. The magnetic field points horizontally to the right and the strength is 2.30 T.

    The proton enters with a velocity vector that is perpendicular to both the electric and magnetic fields, and the magnetic force is opposite to the electric force.

    Determine the proton speed such that the proton will pass through the space with no deflection, i.e., with a constant velocity vector.

    2. Relevant equations

    I am not sure what equation to use.

    3. The attempt at a solution

    Can someone please help? I'm not sure where to begin.
  2. jcsd
  3. Oct 19, 2007 #2
    F = qv x B

    You will need to offset the electric force with the force created by qv x B.
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