I'm not sure I know what the paper ball situation is, but I can tell you that especially when working with a set formula in physics, math or chemistry (I'd include biology if I knew any biology) that it is a good idea to write down your givens.
The equation you are given is going to fall apart once you know what your givens are and what they do.
I just looked up the Paper Ball Situation. This is a wonderful piece of physics. It immediately opened up all sorts of treasures once they experimenters thought of using tin foil. Givens are a necessity in such an experiment.
The midpoint of a line can be found using either a compass and straightedge <span>construction or a straightedge and tracing paper construction. </span>true :)
