If you hit somebody weather the person is knocked out, depends upon 2 factors: 1 - The mental condition of your opponent; 2 - How hard you hit the person.   Body Rotation Rotational Momentum – expansion & contraction. Driving motion Pendulum motion
  1. Body Rotation.
Reverse punches exercises in Zenkutsu Dachi. Practice first without paying attention to the returning hand and then practice with pulling the returning hand back twice as quickly as the punch goes out. Your mental condition is very important so now kiai. You must not retract the blow straight away, because after you hit the Ki comes out so you must have it there for just an instant.  
  1. Driving Motion
Lunge punch exercises in Zenkutsu Dachi.
  1. Push with the back foot and use you adductors – Squeezing muscles to bring the back foot to just behind the front foot.
  2. Switch the hips, now the foot of the punching side is in front.
  3. Explode.
  1. Pendulum Motion
When you kick, drive with the hip.   By O'Sensei Kim Hanshi