Hey guys, I am trying to create a 2d simulation of the earth going around the sun. However I am facing an issue. I am not sure what are the forces that apply on the earth in a 2d aspect. I know there is the gravitational pull GM1M2/R^2. I know there is momentum, which is P = V * R, but I have questions regarding it. How do I break it down to a vector? Pi + Pj.. I realize I could probably do something like calculating P and then just doing Pcose(theta)i + Psin(theta)J but what is theta? how do I calculate it? or more like which angle is it? Also does angular velocity have to do with anything here? if so how do I calculate it?. Sorry for the many questions. Its sad to admit.. but I took all the calculus based physics classes like 1.5 years ago plus a quantum mechanics class.. And I forgot most of the stuff after I got a job..