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Central Force

  1. Aug 22, 2005 #1
    I have a problem for this question, please help me

    A particle of mass m is moving in an attractive inverse cubed force given by

    F = -K/r^3, where K>0

    a) Find V(r) and plot V(r) versus r.
    b) Discuss the motion qualitatively by the method of effective potential.
    C) Find E and L when the particle is moving in a circular orbit.
    d) Find the time period of the orbit.
    e) If the orbit is perturbed slightly, what will be the period of small oscillations?
  2. jcsd
  3. Aug 22, 2005 #2


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    What, exactly, have you done so far?
  4. Aug 22, 2005 #3
    I don't know a shape of V(r) versus r
  5. Aug 22, 2005 #4
    <i>I don't know a shape of V(r) versus r</i>

    V is potential energy? Then V(r) is the integral of the force with respect to displacement.

    Edit: make that the negative integral of the force etc.
    Last edited: Aug 22, 2005
  6. Aug 22, 2005 #5
    I find V(r) = -k/2r^2 + L^2/2mr^2
    a part of r^2 of two terms are equal. Which total graph of V(r)
  7. Aug 23, 2005 #6


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    I could interpret V(r) as velocity or potential energy. Also I have no idea what "E"and "L" are. Please be sure you define all terms.
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