  A solution for the Weinstein's Problem in the general framework of
generalized Lie algebroids is the target of this paper. We present the
mechanical systems called by use, mechanical (?; ?)-systems, Lagrange
mechanical (?; ?)-systems or Finsler mechanical (?; ?)-systems and we develop
their geometries. We obtain the canonical (?; ?)-semi(spray) associated to a
mechanical (?; ?)-system. The Lagrange mechanical (?; ?)-systems are the spaces
necessary to develop a Lagrangian formalism. We obtain the (?; ?)-semispray
associated to a regular Lagrangian L and external force Fe and we derive the
equations of Euler-Lagrange type. A new point of view over classical and modern
results about Lagrangian Mechanics are presented.
