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Homework Help: Electric Dipole in a Magnetic Field: Conservation of energy

  1. May 4, 2012 #1
    Please help me with the attached question.

    I don't understand how you get from the first line to the second line in (2). (I'm not too familiar with working with cross products and vectors).

    Also, I don't know how you get (5) from (1) and (2).

    Any help would be much appreciated. Thanks! :)

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  2. jcsd
  3. May 4, 2012 #2
    (2) the equality Comes from [itex]\vec{v}_{cm} = \dfrac{1}{2}(\vec{v}_1+\vec{v}_2)[/itex]
    (5) Try to wite down the full expression [itex] E = \dfrac{1}{2}mv_{cm}^2+\dfrac{1}{2}I\omega^2[/itex]
    Using (1) and (2)
    And take the time derivitative(here dE/dt is indicated with a small dot above). Then you would see that the energy is conserved.
  4. May 6, 2012 #3
    Thanks dikmikkel! :)
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