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Homework Help: Deriving Vr and V(sub-theta) from Kepler's second law and

  1. Sep 24, 2010 #1
    Deriving Vr and V(sub-theta) from Kepler's second law and....

    1. The problem statement, all variables and given/known data

    Beginning with r=[a(1-e2)]/(1+e*cos [tex]\theta[/tex]) and Kepler's second law, derive general expressions for vr and v[tex]\theta[/tex] for a mass m1 in an elliptical orbit about a second mass m2. The final answers should be functions of P, e, a, and [tex]\theta[/tex] only.

    P=orbital period
    e=eccentricity
    a=semimajor axis

    That's supposed to be v(subtheta) and cosine of theta!

    2. Relevant equations

    A'(t)=L/(2*[tex]\mu[/tex])
     
  2. jcsd
  3. Sep 24, 2010 #2

    diazona

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    Re: Deriving Vr and V(sub-theta) from Kepler's second law and....

    [itex]v_\theta[/itex], understood. What have you done so far and where exactly did you get stuck?
     
  4. Sep 26, 2010 #3
    Re: Deriving Vr and V(sub-theta) from Kepler's second law and....

    Not far at all. I don't even know where to begin. If you do, then please start me off. Thanks!
     
  5. Sep 26, 2010 #4

    diazona

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    Re: Deriving Vr and V(sub-theta) from Kepler's second law and....

    Well, here would be my first thought: you have some information about position, and you are asked to find velocity. What does that tell you?
     
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