DYNAMIC EXPLANATION ON REVERSE ROTATION OF A TOP AFTER CONTACT WITH A PLANE

When a rotating top becomes instable due to the attenuation of rotating speed, and contacts with a plane after falling, an abnormal phenomenon can be observed that the top rotates shortly in the opposite direction before stopping. In present paper a dynamic explanation for this phenomenon is provided. It is shown that the oblique impact during plane-contact is the root cause of the reverse rotation. The possible motions after plane-contact caused by different collision impulse are discussed.