Dresden 2006 – scientific programme

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DY: Dynamik und Statistische Physik

DY 27: Granular Matter and Contact Dynamics II

DY 27.1: Talk

Tuesday, March 28, 2006, 16:30–16:45, SCH 251

Can one hear the shape of a ball? — •C.A. Krülle — Experimentalphysik V, Universität Bayreuth, D-95440 Bayreuth

The coefficient of restitution for the impact of a ball falling on a smooth horizontal surface can be measured by utilizing a very simple and practical method originally suggested by Alan D. Bernstein (Am. J. Phys. 45, 41 (1977)): The typical ticktack generated by multiple collisions between the bouncing object and the underlying plane is recorded by use of a microphone connected with the sound card of a PC. From this the restitution coefficient can be derived easily as the ratio of successive time intervals between sound signals. If the falling object is not precisely spherical the obtained values for the coefficient of restitution will scatter depending on - among other things - the degree of ellipticity. A careful analysis of this dependence shows that modern audio recording devices have been developed to such a high level that even deviations in the micron range can be detected and thus No-dqheardNo-dq by a careful listener.