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Small oscillations

  1. Feb 16, 2009 #1
    1. The problem statement, all variables and given/known data

    A particle of mass m and charge q can move along a vertical circle of radius R in the constant gravitational field of the earth. Another charge q is fixed to the lowest point of teh circle.
    Find the equilibrium position and the frequency of small oscillations of the particle.

    2. Relevant equations

    3. The attempt at a solution

    I'm really lost and have no idea how to solve this problem. Any help would be great...
  2. jcsd
  3. Feb 16, 2009 #2


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    Welcome to PF :smile:

    You can start by listing the forces that act on the particle. What expressions/equations describe those forces?
  4. Feb 22, 2009 #3
    Hi RedBelly,

    Thanks for your reply. I would say the forces acting on the particle are the coulomb forces exerted on it by the other charge. the corresponding equation is

    F = q1q2/r^2, but I'm not sure if this is the only force acting on it, because there must be another force that keeps it to move on the circular path.

    I think I first have to fnd the potential energy so that I can find both the equilibrium position and the frequency of small oscillations, but I still don't know how to do that, especially as I have no idea how express the two conditions

    1) that the particle be on a circular path and
    2) that there be another charge at the lowest point

    by an equation.

    Please help me! I really need to understand this because I will soon have an exam where this kind of questions will be asked.
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