Junjie Shen

In this physics paper, we investigate the rotational behavior of a ring sliding down a vertical steel rod. In previous studies, the ”chatter ring” toy’s motion on a rod was explored, focusing on one-point and two-point contact dynamics. However, these studies neglected the ring’s thickness and lacked quantitative experimental validation. This paper specifically investigates the uniform motion of the ring’s center of mass during two-point contact on a rod. A kinematic and dynamic model, accounting for ring thickness, is established. The paper provides a theoretical derivation that is more accessible for high school and undergraduate students, conducts extensive experimental verification of the accuracy of the theoretical formulas, and semi-quantitatively analyzes the impact of various parameters on this type of motion. Hope the above work vividly demonstrates this interesting and extraordinary motion, where the ring on the rod make contact at two points and undergo pure rolling along the instantaneous axis of contact. This experiment, both simple and suitable for classroom demonstrations, aims to ignite students’ interest in analyzing rigid body motion. It simultaneously offers a challenging aspect, adding an engaging dimension to the learning experience.