  The motion of a composite system made of N particles is examined in a space
with a canonical noncommutative algebra of coordinates. It is found that the
coordinates of the center-of-mass position satisfy noncommutative algebra with
effective parameter. Therefore, the upper bound of the parameter of
noncommutativity is re-examined. We conclude that the weak equivalence
principle is violated in the case of a non-uniform gravitational field and
propose the condition for the recovery of this principle in noncommutative
space. Furthermore, the same condition is derived from the independence of
kinetic energy on the composition.
