## Perpendicular velocity of planets

Hi

I am making a solar system emulation. I need some fairly precise velocities for the planets as a start velocity of the planets and since i calculate the gravity i need it perpendicular in a known distance from the sun.

First of all.. is it correct that if i calculate gravity i would only need the 'start'-velocity(perpendicular) of the planet to be able to simulate a correct path around the sun?

i have searched the web and i don't know where to find them any help?

Kasper

 this may help although its not exactly what you're looking for: http://www.sjsu.edu/faculty/watkins/orbital.htm
 Mentor Welcome to PF, If you assume the orbits are circular, then you can figure out what the speed (which is constant) is just based on the radius. Of course, the orbits aren't circular, they're elliptical. But given key numbers for each orbit, like the eccentricity and semi-major axis, you can determine what the speed is at any point in the orbit. These numbers are what you need to model things correctly.