Coefficient of restitution of colliding viscoelastic spheres

We perform a dimension analysis for colliding viscoelastic spheres to show that the coefficient of normal restitution epsilon depends on the impact velocity g as epsilon=1-gamma(1)g(1/5)+gamma(2)g(2/5-)+..., in accordance with recent findings. We develop a simple theory to find explicit expressions for coefficients gamma(1) and y(2). Using these and few next expansion coefficients for epsilon(g) We construct a Pade approximation for this function which may be used for a wide range of impact velocities where the concept of the viscoelastic collision is valid. The obtained expression reproduces quite accurately the existing experimental dependence epsilon(g) for ice particles. [S1063-651X(99)10410-0].