Cyclotron analog applied to the measurement of rolling friction

Abstract

A simple and inexpensive analog of the cyclotron, ideal for demonstrating the concept of the cyclotron to large classes, is presented. A metal ball, constrained by a centrally directed spring force to follow a circular path over a plane surface, is accelerated by an alternating gravitational force provided manually. A simple method of recording the orbital radius of the ball in the analog provides a sensitive method of measuring the velocity dependent rolling friction force, F=a+bv. Values of a and b for rough and smooth wood surfaces are found and the mechanism by which the losses associated with rolling friction arise is discussed.