Coefficient of restitution mediated by a diamagnetic interaction

Abstract

We study how a magnetic bead bounces onto a horizontal diamagnetic conducting plane. The bead, falling down by gravity from a certain height, produces an Eddy current that creates a repelling force. For low velocities the bead is trapped by the surface, for intermediate ones it escapes. In such a case the induced current changes its sign, and so does the force. The balance between diamagnetic and viscoelastic interactions determines the bouncing dynamics. We find experimentally the restitution coefficient as a function of the impact speed of the bead and develop, taking into account simple energetic considerations, a model able to reproduce our findings.