ABSTRACT
Right part of Figure 1 reports a typical recording of the signal from the force sensor; it exhibits a series of peaks of different amplitude, labeled I here after, at different instants. Each peak corresponds to an impact; its intensity is proportional to the ball speed, as it has been calibrated using impacts from 1 ball experiments. So, the experiment consists of studying the number of collisions as functions of the number of balls in the cell, of the typical piston speed V = bω, of its frequency f =ω/(2π) and of the vibration amplitude b. The statistics are issued from the 16 central seconds of the 20 s of 0-g condition, in order to limit noise.
