Collisions and Mechanical Wave Propagation in Elastic Rods

Abstract

Some results from experiments intended to measure the propagation speed of sound waves produced by collisions between small bodies and metallic rods are analysed. Elementary models of elastic collision and of the refl ection and transmission of waves at media boundaries are discussed and tested with experimental data, in the framework of a workshop on mechanical wave propagation that featured at the University of Palermo in a two-year graduate programme for prospective physics teachers and in courses for undergraduate engineering and physics students.

Energy loss in cue-ball collisions

“…If some of that wave energy is absorbed by the hand, then energy will be lost during the impact. It is difficult to quantify the effect but other experiments with colliding springs and rods [3][4][5][6][7] show that the energy in acoustic waves can be relatively large. For example, if a short rod of length L 1 collides with a long rod of length L 2 at rest then the short rod is predicted to come to rest and a fraction 1 − L 1 /L 2 of the initial kinetic energy is converted to acoustic energy.…”