  We consider the motion of a particle in a uniform field in noncommutative
space which is rotationally invariant. On the basis of exact calculations it is
shown that there is an effect of coordinate noncommutativity on the mass of a
particle. A particular case of motion of a particle in a uniform gravitational
field is considered and the equivalence principle is studied. We propose the
way to solve the problem of violation of the equivalence principle in the
rotationally invariant noncommutative space.
