A solid rod of length l and mass M can rotate around a horizontal axis passing through its end. By the same axle is suspended from a mathematical pendulum of the same length and mass m. Initially, the rod is held in a horizontal position and then released. As a result of an elastic rod and strike the ball pendulum part of the kinetic energy is converted into potential energy of deformation and then back into kinetic energy. Find the value of strain energy at a time when it is maximal.

Detailed solution shorthand terms, formulas and laws used in the decision, the withdrawal of the calculation formula and the response.
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