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Homework Help: Kepler Problem

  1. Feb 22, 2009 #1
    1. The problem statement, all variables and given/known data

    plot the orbit of two masses using the equation for an ellipse and coordinate system at one of the foci

    Masses Initial Positions Initial Velocities
    i mi x1 x2 x3 v_1 v_ 2 v_ 3
    1 1 0.651 0.585 -0.238 -0.755 -0.828 -0.865 -0.726
    2 0.931 -0.096 0.000 0.357 -0.209 0.107 -0.660

    2. Relevant equations

    [tex] \mathbf{r} = \mathbf{r_1} - \mathbf{r_2} [/tex]


    [tex]\varepsilon = \sqrt{1 + \frac{2EL^{2}}{k^{2}\mu}}[/tex]

    [tex]L=\left|\mathbf{L} \right|=\left| \mathbf{r} \times \mathbf{p}\right| [/tex]

    [tex] \mu = \frac{1}{\frac{1}{m_{1}} + \frac{1}{m_{2}}} = \frac{m_{1}m_{2}}{m_{1} + m_{2}} [/tex]

    [tex] E =\frac{\mu \dot{r}^2}{2} -\frac{k}{r} + \frac{L^2}{2\mu r^2} [/tex]

    [tex] k = - G m_1 m_2 [/tex]

    3. The attempt at a solution

    so all i have to do is plot r a function of theta which seems simple enough. the equation for the conic section only has two parameters i don't know E and L. so from what i understand both are constant of motion so i was so i can just evaluate them at the initial conditions plug them into, the formula and plot? am i right?

    to check i calculated the eccentricity: 1.11843. could someone check to make that's one should get for the relative orbit of the light one to the heavier one?
    Last edited: Feb 22, 2009
  2. jcsd
  3. Feb 22, 2009 #2
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