There are two videos: the first is what you're used to from me, and the second is by the author of our textbook. Check them both out. Also, use this INTERACTIVE FIGURE to help with your understanding. Note how the distances the three people travel differ depending on their distances from the axis. The author also has this SCREENCAST that should help. By the way, some of the questions on the quiz refer to our activities in class. I told you to pay attention!
Source: Hewitt, P. G. (2015). Conceptual Physics (12th ed.). Boston, MA: Pearson.
Source: HEWITT, P. G. (2015). CONCEPTUAL PHYSICS (12TH ED.). BOSTON, MA: PEARSON.