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Homework Help: Coulomb's law

  1. Feb 4, 2013 #1
    1. The problem statement, all variables and given/known data
    You have two identical tiny conducting spheres: sphere A carries positive charge qA, and sphere B carries negative charge qB. First the spheres are placed distance d = 0.404 m apart, and they attract each other with a force F1 = 0.748 N. Then the spheres are brought together, touch each other, and are brought back to distance 0.404 m apart. Now the spheres are both positive, and they repel each other with force F2 = 0.59 N. Find the original charge on each sphere.

    2. Relevant equations
    F=k q1q2/r^2

    3. The attempt at a solution
    after the spheres touch i get qf=(q1+q2)/2
    and i solve for the charge on the spheres after they touch and get .1035uC as my answer but im not sure how to find original charge after that my proffesor never did an example like this any help is welcome and appreciated
  2. jcsd
  3. Feb 4, 2013 #2
    Re: coulombs law

    Charge is conserved. Make use of that along with F1.
    Besides, this belongs in the introductory physics section.
    Last edited: Feb 4, 2013
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