Numismatic gyrations

Abstract

It is true that there are a number of possible dissipative mechanisms for the rolling disk in addition to viscous dissipation in the surrounding air: vibration of the supporting surface, rolling friction due to plastic deformation at the point of rolling contact, and, as suggested by van den Engh et al. , dissipation due to slipping rather than rolling. The 'adiabatic' equation that I used, relating the precessional angular velocity Ω to the angle α, is valid only under the rolling condition, and experiments indicate that this condition is indeed satisfied for the 'toy' Euler's disk rolling on a flat, smooth horizontal glass plate placed on a firm table (V. A. Vladimirov, personal communication). I believe therefore that slipping does not occur in this case.