  Composite system made of $N$ particles is considered in twist-deformed
space-time. It is shown that in the space the motion of the center-of-mass of
the system depends on the relative motion. Influence of deformation on the
motion of the center-of-mass of composite system is less than on the motion of
individual particles and depends on the system's composition. We conclude that
if we consider commutation relations for coordinates of a particle to be
proportional inversely to its mass, the commutation relations for coordinates
of composite system do not depend on its composition and are proportional
inversely to system's total mass, besides the motion of the center-of-mass is
independent of the relative motion. In addition we find that inverse
proportionality of parameters of noncommutativity to mass is important for
considering coordinates in twist-deformed space as kinematic variables and for
preserving of the weak equivalence principle.
