It Has to Go Down a Little, in Order to Go Around- Revisiting Feynman on the Gyroscope

摘要

In this paper we show that with the help of accessible, teaching-quality equipment, some interesting and important details of the motion of a gyroscope, which are typically overlooked in introductory courses, can be measured and compared to theory. We begin by deriving a simple relation between the dip angle of a gyroscope released from rest and its precession velocity. We then describe an experi-ment that measures these parameters. The data are in excellent agreement with the theoretical prediction. The idea for this project was suggested by the discussion of gyroscopic motion in The Feynman Lectures on Physics. Feynman's (Fig. 1) conclusion (stated in colloquial language and quoted in the title) is confirmed and, in addition, conservation of angular momentum, which underlies this effect, is quantitatively demonstrated.