# Velocity required for pendulum to make a full swing

I have a conceptual question about the problem, I'm not requesting a solution. I just don't know how to implement the condition of the full swing. I know that the tension at the top is zero. But if I get the velocity from there, how does that help me? I know the velocity of the object at the top of the circle. How does that ensure that it makes a full circle? How do I know that it won't fall off after a while before completing a circle?

• The solution depends on how the pendulum is realized/defined. Either a mass moving along a circle (constraint of fixed distance from the rotation center, implemented, for instance, with a massless rod) or a mass attached to a flexible wire. Jan 8, 2023 at 16:23
• @GiorgioP it's a simple pendulum. A bob on a massless inextensible string.
– EM_1
Jan 8, 2023 at 16:33
• How does that ensure that it makes a full circle? How do I know that it won't fall off after a while before completing a circle? Simple penduli don't complete full circles.
– Gert
Jan 8, 2023 at 16:40