I wouldn't assume the manipulator's recoil is actually the conservation of momentum operating along the vector between the object and Gordon. Much more likely there is a defined, predictable and localised force which occurs when the manipulator discharges its energy, otherwise the recoil would be in proportion to each individual object's mass - which it isn't... Paint cans recoil the same as metal barrels... Clearly the opposing momentum of the object never reaches Gordon, only the manipulator’s own local discharge affects Gordon.