# Solving a projectile problem with mathematica

1. Mar 12, 2007

### Lewis

I am trying the solve the following diff. eq. with NDSolve in mathematica:

$\ddot{x}(t) = - \frac{GMx(t)}{(x(t)^2+y(t)^2)^{\frac{3}{2}}}$
and
$\ddot{y}(t) = - \frac{GMy(t)}{(x(t)^2+y(t)^2)^{\frac{3}{2}}}$

where $GM=3.6018*10^{14}$, the initial conditions are:
$x(0)=0, y(0)=6000000$
and $vx0, vy0$ can be whatever.

The trouble is, I keep an error of some sort. I do not have a huge amount of experience with NDSolve so I am most likely doing something simple wrong. The latest thing I have tried is included as an attachment, and resulted in the error:
NDSolve::ndnum: Encountered non-numerical value for a derivative at t == 0.`.

If someone can point out what I'm doing wrong I would be very gratefull. I also have access to Maple if you know how to solve the problem using that, instead of Mathematica.
Thanks

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