Ooo! I did this one a while back.
Ok the reason you missed the first one is because U @ point a does NOT equal K @ point B. U+K @ a does though. Don't forget it's initially moving.
Orbiting Bodies Question
2. Two stars, A and B are in circular orbits of radii ra and rb, respectively, about their common center of mass at point P. Each star has the same period of revolution T.
Determine expressions for the following three quantities in terms of Ra, Rb, T, and fundamental...