Trajectory calculations

Here's a quick snippet of C code that illustrates the algorithm I was talking about today. Some key bits are missing, but it should give you an idea of what to do.

You start with the initial velocity and parameters, and from that calculate everything a time increment dt later. Repeat for many (many) such dt ...

If you don't read C, I can translate it to some other language upon request. If you request something odd like postscript or the like it may take longer ...

Note also that this only calculates the trajectory given some initial inputs. What you want is the launch angle that gives a certain range ... calculating the trajectory is only a portion of that problem.

while (y>=0) {

v = pow((vx*vx)+(vy*vy),0.5);
theta = atan(vy/vx);
ax = ... ; // get these from your force equation
ay = ... ;
vx = vx + ax*dt;
vy = vy + ay*dt;
x = x + vx*dt+0.5*ax*dt*dt;
y = y + vy*dt+0.5*ay*dt*dt;
if (y<0)
y=0; // negative y means we hit the ground
// store various values here
t+=dt;

}