Originally Posted by
cyccommute
No, you don't get thrown up. Your center of gravity continues in the same line it was going it before the crash. Basic physics.
Usually, you go over the bars because your front wheel has slowed. So , unless the fork crumples, the bike has little choice but to pivot over the slower moving wheel. Your head goes forward, yes, roughly parallel to the ground, but the bike seat goes up, taking your butt with it. Now your butt is higher than it was and has more potential energy to impart to your head when it slows as it contacts the ground.