When we convert yards to seconds we get the following: (40 yard) / (4.7 seconds) = 17.4081238 mph. Thanks! AnswerParty rocks!
The 40-yard dash is a sprint covering 40 yards (36.58 m). It is primarily run to evaluate the speed of American football players by scouts, particularly for the NFL Draft but also for collegiate recruiting. A player's recorded time can have a heavy impact on his prospects in college or professional football. This was traditionally only true for the "skill" positions such as running back, wide receiver, and defensive back, although now a fast 40-yard dash time is considered important for almost every position. The 40-yard dash is not an official race in track and field athletics and is not an IAAF-recognized event.
The origin of timing football players for 40 yards comes from the average distance of a punt and the time it takes to reach that distance.]citation needed[ Punts average around 40 yards in distance from the line of scrimmage, and the hangtime (time of flight) averages approximately 4.5 seconds. Therefore, if a coach knows that a player runs 40 yards in 4.5 seconds, he will be able to leave the line of scrimmage when a punt is kicked, and reach at the point where the ball comes down just as it arrives. Sports