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Homework Help: A electrostatics problem

  1. Aug 18, 2009 #1
    I am not being able to solve the following problem i would be grateful if any one could help me out.
    here is the problem:
    eight equal point charges each of charge q and mass m are placed at eight corners of a cube of side a.
    if keeping all other charges fixed a charge at a single corner is released then find out the speed when it is at infinite distance.
    even advices on how to proceed would help.
    Thank you.
  2. jcsd
  3. Aug 18, 2009 #2


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    Gold Member

    Your initial configuration is 8 charges assembled at the corners of a cube. Your final configuration is seven charges at the corners of a cube and one charge at infinity with some kinetic energy. Energy conservation says

    Kinitial+Uinitial = Kfinal+Ufinal

    Replace each of the four symbols above with appropriate expressions.
  4. Aug 18, 2009 #3
    Thanks a lot,
    could you please explain me how to find out the energy of the charge at infinity.
    Also can anyone explain me the effect of electric field on a dielectric(non- conducting) medium .
  5. Aug 18, 2009 #4


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    It's usually easiest to define the potential energy at infinity to be zero.
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