- #1
Poirot
- 94
- 2
Homework Statement
I'm trying to plot Newtonian orbits in Mathematica with the goal of extending this to orbits including GR after. I've derived equations for r(t) and ##\phi##(t) (see below) by integrating ##\dot{r}## and ## \dot{\phi} ## (see below also) from E = 1/2mv2 +V(r) with velocity being split into angular and radial terms and V(r) = GMm/r. I think I then need to find an equation for r(##\phi##) to then plot in Mathematica using the ParametricPlot function but I can't see how to do this as my equations for r(t) and ##\phi##(t) are tricky.
Homework Equations
##\dot{r} = \sqrt{\frac2m(E-\frac{GMm}{r})-\frac{L^2}{m^2r^2}}##
##\dot{\phi} = \frac{L}{mr(t)^2}##
##r(t)=\sqrt{\frac2m(E-\frac{GMm}{r})-\frac{L^2}{m^2r^2}} t + r_0##
##\phi(t)=\frac{L}{m}\frac{ln(m\sqrt{\frac2m(E-\frac{GMm}{r})-\frac{L^2}{m^2r^2}} t + r_0m)}{\sqrt{\frac2m(E-\frac{GMm}{r})-\frac{L^2}{m^2r^2}}} + \phi_0 ##
##r(0)=r_0##
##\phi(0)=\frac{L}{m}\frac{ln(r_0m^2)}{\sqrt{\frac2m(E-\frac{GMm}{r})-\frac{L^2}{m^2r^2}}} + \phi_0 ##
The Attempt at a Solution
I tried finding initial conditions at t=0 (see equations above) but I'm not sure if any of this is even right? It seems to have gotten to complicated. If everything I have done so far is correct, I'm not sure how to then find r(##\phi##) and if I was to find this how to convey all this information into a ParametricPlot function in order to obtain the orbits.
Any help would be greatly appreciated, Thanks.