Collisions of two particles in both lab and center of mass frame

We experimentally investigate the dynamics of two spherical particles free to collide in a vertically shaken channel. The identical particles both have a diameter of ??=5.0 ????. Multiple cases are considered for driving frequencies, f, ranging from 23 to 32 Hz and the acceleration magnitudes, Γ, from 1.78 to 3.53 g. The relative velocity and the total mechanical energy of the two particles before and after collisions are examined in both the lab frame and the center of mass frame. Super-elastic collisions, where the coefficient of restitution is measured to be greater than unity, are observed in this experiment. Most of the data suggest a slight mechanical energy loss during the collisions, and a linear fit is applied to obtain the coefficient of restitution between the two particles with a nearly constant value of approximately 0.8. The results of a simulation suggests that the super-elastic collisions result from an occasional mechanical energy transfer between the rotational and translational degrees of freedom.