defense. It tries to stop the offensive team and make it give up possession of the ball in four
downs. If the team with the ball does score or is forced to give up possession after four downs,
the offensive and defensive teams switch roles (the offensive team goes on defense and the
defensive team goes on offense). And so on, back and forth, until all four quarters of the game
have been played. Pro NFL and collegiate football games are divided into four 15-minute
quarters, separated by a 12-minute break at halftime. There are also 2-minute breaks at the end of
the first and third quarters as teams change ends of the field after every 15 minutes of play. At
the end of the first and third quarters, the team with the ball retains possession heading into the
following quarter. That is not the case before halftime. The second half starts with a kickoff in
the same way as the game began in the first quarter.
Each offensive team has 40 seconds from the end of a given play until they must snap of the ball
for the start of the next play, otherwise they will be penalized.
The clock stops at the end of incomplete passing plays, when a player goes out of bounds,
or when a penalty is called. The clock starts again when the ball is re-spotted by an official.If a
game is tied at the end of regulation, a 15-minute overtime period will be played. In the NFL,
this is sudden death and the first team to score within the allotted time does not win unless the
time runs out as they score. If one team scores with time left on the clock then the other team is
given a chance to score also. Possession of the football is determined before the period begins
by a coin toss to start Overtime. This, like many other rules have been changed recently, football
has also changed in the terms of rules, the point system, and the equipment. Specifically for
helmets, David Camarillo’s Ted talk provides information on concussions and the science
behind preventing a concussion. He gives factual evidence and data that shows how concussion