I wish your help in creating a tabletop Newtonian physics demo. My friends do not believe that the centrifugal force is imaginary. They believe that, if you swing a pail of water in a circle over your head and let the rope go, the pail will sail *away* from you (as opposed to tangential to the circle). (see diagram) I am sure that the point of ambiguity is that path A is perceived as if it is really path B, that the confusion lies in not knowing exactly where the snip happens. It is key to understanding that the rope and the path of the bucket are exactly perpendicular to each other a thte point of snippage. This would demonstrate that there is no outward force acting on the bucket - only inertia keeps it moving. I wish to demonstate this in a simple and elegant way. It needs to have - frictionless rotation - a way of cutting the centripetal force bearer (i.e. the thread) while clearly not affecting the path or imparting any other forces - precision, inasmuch as I can show the point of snip, and the precise resultant trajectory I saw this in a high school film, where they used a (frictionless, dry ice-powered, air hockey puck-like) device tied to a post by a thread, and they used a candle to cut the thread. I do not have this equipment. My next thought was a bicycle wheel set on its axle, with a marble in a box, and a trigger. This would work, but it's large, heavy and dirty. Can anyone think of a simple, elegant tabletop mechanism I can setup to demonstrate this?