A Simple Explanation of the Microwave Carousel Problem

Inspired by the Zachary H. Levine’s article 1 I tried to find an explanation for the fact that the speed of the plate is twice higher as the speed of the three-armed frame, which would not involve any calculation and would be understandable even to a seven-year old (hopefully). In the Figure 1. we can see clearly that the total displacement L of the point C of the plate is exactly twice of the displacement of the center of mass O of the wheel of the frame. Because the both movements take the same time, the ratio of the speed is 2.

1.    Zachary H. Levine, “Microwave Carousels – A New Spin on Rollin Contact”, Phys. Teach. 45, 54 (Jan. 2007)