Collisions and concussions

http://www.miaminewtimes.com/news/twenty-six-florida-football-players-sue-the-nfl-for-concussion-related-workers-comp-8943352

Earlier last week, the Miami New Times reported that 26 retired football players from Florida have sued the NFL for worker’s compensations. They demanded such damages charging that the organization remained willfully ignorant of the information that repeated severe concussions can lead to a neurodegenerative condition called chronic traumatic encephalopathy (CTE). The plaintiffs alleged that the NFL was aware of the effect of CTE on its players as early as 1994, but that the organization acted to suppress such facts by injecting misinformation into the public. A major breakthrough was in 2016, when researchers from the University of Pennsylvania found that the level of a brain protein called tau could be used to predict onset of CTE in adults, and discovered that many NFL players were likely experiencing early onset of CTE. The condition is diagnosed in a similar manner as Alzheimer’s Disease is diagnosed, generally based on symptoms displayed, and is characterized by severe memory loss and confusion and later fatality. I attempted to estimate through calculation the kinetic energy delivered during a collision via a tackle, which may involve a physical collision to the head. Although the players are protected by a helmet, those tend to protect against skull fractures on the outside rather than the movement of the brain on the inside which leads to concussions. I assumed that the collision would be inelastic in a tackle and that each player would weigh 250 pounds or 113.4kg (http://www.businessinsider.com/average-height-weight-nfl-nba-players-2014-8) , and that player 1 would collide with player 2 at the speed of 8.02 m/s, according to estimates from Popular Mechanics. (http://www.popularmechanics.com/adventure/sports/a2954/4212171/) 
According to conservation of momentum in inelastic collisions, m_av_ai+m_bv_bi=(m_a+m_b)v_f.

Then the equation would be: 113.4(8.02)+113.4(0)=(113.4+113.4)v; v=4.01m/s.

The kinetic energy of the collision would then be: 1/2*(113.4+113.4)*4.01^2=1823.5J.

The kinetic energy in the collision would roughly be 1800J, part of which, even if a helmet is worn, inevitably would be delivered to the inside of the head and would affect the brain floating within the skull cavity.