The center of a system of non-parallel force

From a discrete system F of applied forces given by a collection of vectors Fk applied to corresponding points Pk\ a new system QF can be obtained through a rotation by Q of all Fk without changing Pk[ In this note we examine invariant properties of F under arbitrary rotations[ We also examine invariant properties of the family QF when all rotations share a _xed axis\ giving a coordinate!free approach to the results of Kolosov "0816