1. The problem statement, all variables and given/known data Hi, the aim of this experiment is the investigate the relationship between the centripetal force acting on an object moving in a circle of constant radius and its frequency of revolution. For the experiment, there is a rubber stopper attached to fishing line, that is passed through a glass tube, and an alligator clip is used to keep the radius constant. Hanging on the fishing line are slotted masses, which are altered in order to alter the weight force, and in turn alter the centripetal force supplied by tension. I have to amend a diagram to include the real rotation of the stopper and draw labelled vectors representing the forces acting on the rubber stopper whilst it is orbiting. I have tried to draw this diagram, but I am unsure as to whether it is correct, and have hence come here in seek of verification. 2. Relevant equations Nil. 3. The attempt at a solution The ideal diagram looks like this, http://img140.imageshack.us/img140/2706/idealdiagram.png [Broken] Whilst the amended one looks like this, http://img338.imageshack.us/img338/6104/amendeddiagram.png [Broken] But with the use of vector addition, I am unsure as to how this produces the tension resultant vector. Shouldn't there be a horizontal force too? If so, what is it? Please help. Thank you in advance.