9b shows

the same condition but in this case the Shinai is metaphorically flung forward on impact and in the crucial instant this has the effect of countering the centripetal effect. The result is the introduction of centrifugal force, along the length of Shinai. The result will be a new penetration angle bisecting the two forces at an angle of forty-five degrees, and an efficient
'slicing' action is implied.
9c shows the force line of the body moving forward and the final angle is again bisected to arrive at a very efficient slicing angle of penetration. In this way the downward cutting action of the stroke is directed forward and the penetration action is implied rather than factual. The Kiai or shout is uttered at his moment and serves to throw the mind and spirit into the Shinai.

10 shows merely the final effect in reverse, when a cut is made with a backward step. In this case the arms are straightened but the Shinai is drawn back in imagination and the whole direction reverses inside the arc of the stroke.