こまの運動に関する一考察

Abstract

We sometimes have difficulties to understand the reason why an ideal top never topples. Physicist might explain that angular momentum conserves. Students could not imagine the fact that a top spins continuously because angular momentum is constant. A pole stands still when pulled radially by many ropes, and no one doubts this. This is also the case for a top spin. Centrifugal and centripetal forces appear instead of the rope tension. In this short note, we first would like to introduce this pole-rope analogy for a spinning top. Secondary, we show that precession can be explained by several concepts. One is Eulerian and another is Feymanian. The last one is Newtonian. Euler's and Feyman's interpretations both base on the conservation of angular momentum. Newtonian approach shows that actually Coriolis' force play an important role for mischievous gyro moment.