Pretty basic and not fully encompassing but informative excerpt on tackling and physics:
http://abcnews.go.com/Technology/story?id=99061&page=1
Physics of Protection
For example, a common football tip to stay low and keep the head up while tackling, is actually just good physics, according to Gay.
"By keeping the feet planted and the head up,
a player can direct where the force of an impact goes," he says. "By directing the force you can make sure
either your equipment or the ground absorbs the shock."
Controlling the force of a tackle is just as important for a 300-pound lineman as it is for a 220-pound quarterback who's taking the hit. That's because when players collide, the force of the impact is distributed equally between them, thanks to a seemingly counter-intuitive law discovered by Sir. Isaac Newton in the 17th century.
Newton's third law of motion says if two objects interact, they exert opposite and equal forces on each other.
"Let's say a bigger player has a momentum of +10 and a smaller player is standing still and has a momentum of 0," Gay explains. "After they hit each other the bigger player's momentum is +5 and the little player's momentum is +5. But the bigger player will most likely determine where they end up."
Even if a player can't control a hit, says David Haas, a physics professor and football buff at North Carolina State University, good players learn to absorb impact in the right places.
"
No matter where the hit is absorbed the total force to the player is the same," says Haas. "
The point is does he want to absorb that force in the ribs or on the shoulder pads?"
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It's probably safe to say most people do not understand the fundamentals of physics and physiology. What many people "know" is what their eyes tell them. However, what's seen is not a complete picture if science is not understood or dismissed.
@Dave_in-NC made an excellent comment in this thread concerning tackling. He alludes to the fact that all tackles aren't equal. Different people have always argued how players sustain injuries from tackling but the fact reveals how very little people know about why injuries happen.
Distribution of force and a players' bodies are the two main factors. In elementary terms,
how a player gets hit (which is sometimes the player doing the hitting)
and/or whether a player suffers from a physiological deficiency determines if an injury will or will not occur. This fact applies to
every player who has or will play a contact sport. It is that simple.
Getting off the soap box and back to reading ignorance-inspired dismissal of something as plain and simple as bad luck.
