The coefficient of restitution |
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Most collisions are inelastic; some energy is converted to heat, and the relative velocity after collision are less than before. The coefficient of restitution is defined as the ratio of the relative velocity after collision over the relative velocity before.  In the simplest case, where the second body (the Earth) remains effectively stationary, the ratio simplifies to v/u.  Steel is relatively elastic and steel ball bearings have a high coefficient of restitution. Rubber is less elastic and the coefficients are lower. For many substances the coefficient of restitution is very nearly constant, independent of the energy of collision. |