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Homework Help: Finding the mass of a sphere with uniform charge density

  1. Sep 26, 2012 #1
    1. The problem statement, all variables and given/known data
    The sphere has radius R, and uniform volume charge density P. This sphere remains stationary (levitates) when placed above an infinite sheet of paper with a uniform surface charge density u. What is this sphere's mass?


    2. Relevant equations
    4/3 pi R^3 is the volume of a sphere
    F=ma

    3. The attempt at a solution
    The only connection between mass and the charged situation I can see is with the Force=ma law, but as there isn't any acceleration, I can't figure out how to solve for m...any help would be appreciated, thanks
     
    Last edited: Sep 26, 2012
  2. jcsd
  3. Sep 26, 2012 #2
    To remain stationary, the net force on the ball should be zero. What are the forces acting on the ball?
     
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