Kinetic energy is relative to the frame of reference, but Changes in kinetic energy is never relative to fixed reference frame. I think people dont realize the

Kinetic energy is relative to the frame of reference, but Changes in kinetic energy is never relative to fixed reference frame. I think people dont realize they are changing their reference frames, and getting insane results like the amount of kinnetic energy release in the collision depend on what frame you pick. two crumple zones don't matter for head on collision, which is another thing that trips people up.