The role that physics plays in tackle football is more relevant now than ever before.  Just this past year National Football League officials changed the rules of the game in order to avoid some of the intense physical danger that comes along with one human tackling another.  The commissioner put through a rule that moved kick-offs up a full 10 yards from where they used to be.  The point being to discourage kick returns from taking place by making it incredibly easy for the NFL’s kickers to kick the football out of the back of the endzone for a touchback.  The physics behind the contact players make throughout the course of a football game is mind-shattering; I mean that in both a literal and figurative sense.

With the mass and speed of NFL players steadily increasing, the momentum behind each and every hit thrown on Sundays has grown to be more and more dangerous.  This has made physics more relevant today in the NFL than it has ever been before.  Current players are more frequently getting concussions and ex-players are coming out and saying their lives have been ruined because of the violent nature embedded in America’s most popular sport.  So, let’s take a look at the physics behind all the madness.

When two players are running full speed at each other on a football field they build up their momentum.  At the point of contact, a tackler must apply an impulse by hitting the ball carrier. Impulse is the product of the applied force and the time over which that force is applied. (1)  Figuring out whether the ball carrier or the tackler has more momentum will allow us to determine which of the two will be knocked backwards. In other words, if a running back hits the hole and makes contact with a linebacker who has less momentum than he does, the linebacker will be driven back and the running back will gain more yards.  If the linebacker is able to build up more momentum than the running back, then he will be able to knock the running back backwards.  The conservation of momentum theory suggests that the total momentum of each player must remain constant both before and after their collision.  This means that if a linebacker and a running back hit each other at an equal momentum they will stop at the point of contact, not a step further in either direction.

1) http://entertainment.howstuffworks.com/physics-of-football4.htm