Abstract
A quantitative experiment where we measure the acceleration of spheres of radius R rolling on an inclined U-shaped profile of width 2D is presented. For a given inclination, we examine the behavior of four solid spheres having different diameters; in contrast to what is usually assumed to be the case, the experimental findings show that the dissipative component of the ball – track interaction can be neglected only in a limited range of the D/R parameter. We develop two interpretative models which are at the level of advanced high school students. The comparison between model predictions and measurements is quite satisfactory.