1. The problem statement, all variables and given/known data An inextensible spring with a longitud [tex]L[/tex] has a body attached on one of its side (at point [tex]Z[/tex] in my figure). The other side of the spring remains fixed (at the center of the circular motion). The body experiment the gravitational force since the circle is in a vertical plane. Calculate the minimal velocity (or speed?) when at point [tex]A[/tex] that must have the body in order to not be deviated from its circular motion. 2. Relevant equations 3. The attempt at a solution I've thought a lot about the problem, but I'm really lost. I know the formulas to encounter the velocity and all this but I don't know how to apply them in this example. I know that if the velocity at point A is 0 then the body will fall vertically. If the velocity is very little then the body will describe a parabola and be deviated from its circular motion... And if he has the velocity I must find, it will remains on its circular motion. I find the problem very interesting but I'm at a loss! I need to be started, like "what happens when the body is at point [tex]A[/tex] and its velocity is the one you are looking for?", because I just don't know.