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Homework Help: Role of mass in this problem on electrostatics

  1. Apr 28, 2012 #1
    1. The problem statement, all variables and given/known data
    Positive charge Q is distributed uniformly over a circular ring of radius R.A particle with mass 'm' and a negative charge 'q' is placed on the axis at a distance 'x' from the centre.Find the force on the particle.Assuming x<<R, find the time period of oscillation of the particle if it is released from there.

    Before I request for a solution, I would request someone to explain why the mass given here is relevant.

    Secondly, can anyone please refer me a book/reference on electrostatics?I am fully comfortable with rigorous single variable calculus(I am in high school) and would not mind a book/reference that has really tough problems but explains the matter well.(My assessment is that I have not really understood the matter)

    Edit:I can probably see that the x<<R condition is for approximation(or for some ignoring some quantity when it emerges in the answer or the steps leading to it)
  2. jcsd
  3. Apr 28, 2012 #2

    Why not?

    To find the electrostatic force, i think (and i'm sure), the mass is'nt necessary.

    But maybe for the time of oscillation no? I dont know.

    So... You should to read Richard Feynman's books.
  4. Apr 28, 2012 #3
    You are going to find a force which acts more or less like a spring (F = kx). Since you know that F = ma = md2x/dt2, you're gonna wind up with a diff.eq. with m in it. The solution to it is a sine wave, in which you'll find your time constant.

    spoiler: You are gonna have to find the e-field by integrating the line charge, which in turn yields the force as F=qE.

    ps.Electromagnetic Fields by Wangsness is the best book on electromagnetism in my opinion, but it requires multi-variable.
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