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Homework Help: Electrostatic Potential of 4 charged spheres on corners of a square

  1. Feb 13, 2010 #1
    1. The problem statement, all variables and given/known data
    Four idential charged spheres are located at the corners of a square with side length 2a. The spheres are much smaller than the size of the square (r<<a) and each sphere has a mass m and carries the same charge -Q.

    a) What is the total electrostatic potential energy of the combined 4-sphere system when arranged as described?
    b) How much kinetic energy does a sphere gain by moving very far away from the other three?
    c) What is the speed of a sphere moved very far away?


    2. Relevant equations
    Utot=kq1q2/r
    KEf=Ui
    KE=1/2mv^2


    3. The attempt at a solution
    For part a, I think i got the right answer: Utot=k(4root2q^2+2q^2)/root2r

    b)KE=1/2(4m)v^2 and thats it because thats all we know

    c) I used Ui=Kf
    so k(4root2q^2+2q^2)/root2r=1/2(4m)v^2

    and solve for v to get

    v=squareroot(k*2q^2/mr+q^2/root2mr)
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Feb 14, 2010 #2
    im just wanting to know if im right
     
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