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Homework Help: Electric Potential Energy Among Multiple Charges kinda a

  1. Jun 3, 2010 #1
    Electric Potential Energy Among Multiple Charges kinda aurgent

    1. The problem statement, all variables and given/known data

    Four point charges, fixed in place, form a square with side length d. (See image)

    http://i23.photobucket.com/albums/b354/h4llw4x0r/notSoFast.jpg

    The particle with charge q is now released and given a quick push; as a result, it acquires speed v. Eventually, this particle ends up at the center of the original square and is momentarily at rest. If the mass of this particle is m, what was its initial speed v?
    Express your answer in terms of q, d, m, and appropriate constants. Use k instead of 1/4πe (where e = epsilon). The numeric coefficient should be a decimal with three significant figures.

    2. Relevant equations

    - Electric Potential Energy equation: U = k((Q1*Q2)/r)
    - Relative Kinematics Equations


    3. The attempt at a solution

    Ui+Ki=Uf+Kf

    Kf=0
    you get following
    Ki=-Ui+Uf

    getting the potential for each charge
    solving for v
    v==[((2kq^2)/dm)((9/(.5^.4))-5-((5/(2^.5))]^.5 then simplifying
    i got v=[((2kq^2)/dm)(4.192)]^.5
    is this correct
     
    Last edited: Jun 3, 2010
  2. jcsd
  3. Jun 3, 2010 #2

    ehild

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    Homework Helper

    Re: Electric Potential Energy Among Multiple Charges kinda aurgent

    Show your work, please.

    ehild
     
  4. Jun 3, 2010 #3
    Re: Electric Potential Energy Among Multiple Charges kinda aurgent

    i got it
     
  5. Jun 3, 2010 #4
    Re: Electric Potential Energy Among Multiple Charges kinda aurgent

    v==[((2kq^2)/dm)((9/(.5^.4))-5-((5/(2^.5))]^.5 then simplifying
    i should not get this v=[((2kq^2)/dm)(4.192)]^.5
    i should get the following (6.24kq62/dm)^.5
     
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