  One of important problems in mathematical physics concerns derivation of
point dynamics from field equations. The most common approach to this problem
is based on WKB method. Here we describe a different method based on the
concept of trajectory of concentration. When we applied this method to
nonlinear Klein-Gordon equation, we derived relativistic Newton's law and
Einstein's formula for inertial mass. Here we apply the same approach to
nonlinear Schrodinger equation and derive non-relativistic Newton's law for the
trajectory of concentration.
