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Q: Watching the Packers the other day, I was impressed with the players' ability to keep playing considering how often and how hard they block and tackle. Just how hard do they collide?
A: Head-on-head collisions can impart more than 1,000 G forces to players' helmets (that's 1,000 times the force of gravity), with about 100 to 200 G's on the players' heads, making it seem as if the head weighed more than a ton, according to Nelson Kraemer of Riddell Inc., a company that makes football helmets. Such forces would be lethal except that they're applied for mere thousandths of a second (from 0 G's to 150 G's, then back to 0 G's in 0.005 of a second or so).
The reason injuries don't...