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Homework Help: Electromagnetic rail gun

  1. Mar 12, 2010 #1
    1. The problem statement, all variables and given/known data

    An electromagnetic rail gun can fire a projectile using a magnetic field and an electric current. Consider two parallel conducting rails, separated by 0.575 m, which run north and south. A 49.0-g conducting rod is placed across the tracks and a battery is connected between the tracks, with its positive terminal connected to the east track. A magnetic field of magnitude 0.750 T is directed perpendicular to the plane of the rails and rod. A current of 2.00 A passes through the rod.

    If there is no friction between the rails and the rod, how fast is the rod moving after it has traveled 8.00 m down the rails? What direction is the force on the rod?

    2. Relevant equations

    F = qVxB (where V and B are vectors)
    F = I LxB
    a = ILB / m

    3. The attempt at a solution

    a= (2.0 A)(0.575m)(0.750T)
    a = 0.8625 m/s

    I've drawn the picture and can determine (see) that the force in in the North direction. So I just need help figuring out the acceleration. I think there must be some cross products but don't really understand how to do that.

    Thanks in advance for your help.
  2. jcsd
  3. Mar 12, 2010 #2


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    Homework Helper

    Didn't you already calculate the acceleration? The unit should be m/s^2, not m/s.
  4. Mar 12, 2010 #3
    Sorry, I got confused.

    So then to answer the actual question I multiply 0.8625 by 8.0 meters

    (0.8625)(8.0) = 6.9 m/s^2

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