After the ball is well on it's way, momentum and centrifugal force of the bat will "pull" the back arm to full extension.
(the ball; is; well on) (it; 's; way, momentum and centrifugal force of the bat; T:After the ball is well on)
the ball it
is 's
well on
way, momentum and centrifugal force of the bat T:After the ball is well on