Remember, JFK was NOT driving the car~
There is another reason JFK’s shooting is a bad example. A detailed computer analysis of the Zapruder film shows that his head did start to go forward from the impact of the bullet. But he was in a car moving forward and a moment later the guy who was driving it accelerated that momentum even more. With little or no control over his body after the moment of impact that left him a limp rag doll and the forward momentum of the car cause his head to whip back. It wasn’t bullet ballistics that caused that backward motion.