They simply argue that by maximizing the inertia of the sphere during the motion along the lateral arms, motion can be favored in that direction. Here's the co

They simply argue that by maximizing the inertia of the sphere during the motion along the lateral arms, motion can be favored in that direction. Here's the concept you're most likely missing, as taught and demonstrated by Walter Lewin https://www.youtube.com/watch?v=lvfzdibrUFA https://www.youtube.com/watch?v=lvfzdibrUFA