2D orbital physics

Question

I\'m working on a 2D physics engine for a game. I have gravity and masses working, using a simple iterative approach (that I know I\'ll have to upgrade eventually); I can push t

Answer 1

Yes, these equations hold in 2D space, because your 2D space is just a 2D representation of a 3D world. (A "real" 2D universe would have different equations, but that's not relevant here.)

A long shot: Are you perhaps using distance to the surface of the planet as r?

If that isn't it, try cutting your time step in half; if that makes a big difference, keep reducing it until the behavior stops changing.

If that makes no difference, try setting the initial velocity to zero, then watching it fall for a few iterations and measuring its acceleration to see if it's GM/r². If the answer still isn't clear, post the results and we'll try to figure it out.