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Homework Help: Magnetic forces/magnetic fields

  1. May 31, 2007 #1
    1. The problem statement, all variables and given/known data

    A .2Kg metal rod carrying a current of 10A glides on two horizontal rails .5m apart. What vertical magnetic field is required to keep the rod moving at a constant speed if the coefficient of kinetic friction is .1?

    2. Relevant equations

    3. The attempt at a solution

    F (magnetic) = B I L (B is vertical to L)
    F (friction) = mew * mg
    where mew = 0.1 =coeffi of friction
    BIL = 0.1 * 0.2*9.8
    B = 0.1 * 0.2*9.8/10*0.5
    B = 0.0392 Tesla vertically

    acceleration of rod = m dv/dt = F (mag) - F (fric) = 0
    dv/dt =0
    v = constant

    is this the right setup? or am I heading no where?
  2. jcsd
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