Compression waves and kinetic energy losses in collisions between balls and rods of different lengths

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

We report investigations of collisions between steel balls and free-ended rods using an electro-mechanical apparatus combined with a Michelson interferometer. Our experimental methodology allows for the evaluation of several collision-initiated parameters, such as collision duration, speed of the inter-material wave pulse, change in rod length, and post-collision center-of-mass velocity. The fractional loss of kinetic energy of the ball-rod system is studied theoretically and experimentally as a function of the rod length. Results are compared to predictions obtained from the elastic-body collision theory. Several aspects of elastic waves are illustrated without recourse to complicated mathematics. The experiment provides significant insight into the physical behavior of colliding solids. (C) 2014 American Association of Physics Teachers.