1. Two particles of equal mass are orbiting each other in circular orbits. What is the radius at which they orbit? Energy = T + U = 0 (for circular orbits) T = 1/2 m v^2 U = -(Gm*m)/r + [L^2] / [2(mu)r^2] period=[2 pi r] / vt vt is tangential velocity L is angular momentum mu is a constant G is the gravitational constant r is the radius from one particle to the center of their rotation I have attempted to solve for R by plugging those equations in and simplifying, but I do not believe my answer is correct (it would require a lot of skill to represent it with mere type here). I must calculate the radius in order to find the time it takes for the two to collide if they were stopped in their orbits and fell towards each other. So any help calculating the velocity?