**DIPS 1/2001**[tex source, PostScript, PDF file, dvi]-
**Title:**Geometry of inelastic collisions**Authors:**F. Pugliese, A. M. VinogradovA general geometric method for studying mechanical systems whose phase space may undergo an abrupt reduction is proposed. This method is based on a variant of the Transition Principle, proposed for the first time in Appendix II of paper by Vinogradov, A.M., Kupershmidt, B.A.,

*The Structures of Hamiltonian Mechanics*, Russ. Math.Surv.**2**(1977) for elastic collisions.

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