Hello, I had some questions on escape velocity. The only methods that I have seen on escape velocity involve the assumption that the mass which is "being escaped from" remains at rest (at a fixed point in space). For example the method of determination of escape velocity using Ki+Ui=Kf+Uf seems to be useful only if the first mass is assumed to be at a fixed point in space. If there are other methods of determining escape velocity which account for the acceleration of the "mass which is escaped from" towards the "mass which is escaping" please point me in that direction. I was also wondering if anyone knew how to calculate the escape velocity for a single mass in a system of three or more different masses at different points in space? Thank you.