As an avid
football fan, I spend every weekend watching hours of NFL action. Any football
fan will tell you they love to see the big hits. I’m no different. In watching
this weekend’s games, I found myself wondering exactly how hard do they hit and how fast
are these athletes moving when they deliver these devastating blows? I did some
research on average weight and speed stats for various positions for athletes
performing at the NFL combine and used these in our kinematic and Newtonian
equations to find out for myself. (Note, for ease of calculation, I’ve ignored
wind resistance and assumed constant acceleration. All calculations are completed assuming 40yards of running distance.)

Cornerbacks:
While not the biggest guys on the field, corners make up for their lack in size
with blazing speed. Average 40yd times for cornerbacks in the past 5 years at
the combine clock in at 4.55seconds. Using the kinematic equation Δx=V

_{°}t+½at^{2}(again assuming constant acceleration) I found that the average NFL corner can accelerate at 3.56m/s^{2}. Using the equation V=V_{°}+at I found that at the end of the 40 yards, corners are running at an average speed of 16.2m/s or 36.2mi/hr. With an average mass of 87.5kg, these corners can deliver a force of impact of 312N (after a 40yard running start, that is) (using the equation F=ma).
Linebackers:
These big boys rely on their size to punish running backs and receivers unlucky
enough to find themselves in the way of the oncoming pain train. Average 40yd
times for linebackers in the past 5 years at the combine clock in at 4.77seconds.
Using the same equations as above, I found that the average NFL linebacker can
accelerate at 3.25m/s

^{2}. At the end of the 40yds, ‘backers are traveling at an average speed of 15.5m/s or 34.7mi/hr. With an average mass of 109kg, ‘backers plow into the offense with a force of 354N.
Safeties:
The last line of defense. These gifted athletes averaged a 40yd time of 4.62seconds
over the past 5 years at the combine. Using this time, I found that safeties
can accelerate at 3.46m/s

^{2}. At the end of the 40yds, safeties are traveling an average speed of 16.0m/s or 35.8mi/hr. With an average mass of 94.8kg, safeties run over the competition with a force of 328N.
Needless to say,
I don’t think I’d want to be on the wrong end of an NFL defender moving at full
speed.