Placeholder Image

Subtitles section Play video

  • LESTER HOLT, reporting: From big and bulldozing,

  • to small and speedy, NFL running backs come in many shapes and sizes.

  • But to succeed at football, all running backs must excel at

  • kinematics, the branch of classical mechanics

  • that defines how objects move.

  • Dr. TONY SCHMITZ (University of Florida): Because kinematics

  • describes motion, it describes everything an NFL running back

  • does basically, which is his motion up the field as he tries to score.

  • HOLT: Kinematics uses three concepts to define motion:

  • position, velocity and acceleration.

  • Position defines location within a space,

  • such as the surface of a football field.

  • Dr. SCHMITZ: Position would be a running back's location on the

  • field, and he can change that with his motion.

  • HOLT: In this play, let's define the running back's position

  • where he takes the hand-off.

  • After executing the play, however,

  • his new position is his opponent's end zone.

  • Dr. JOHN ZIEGERT (Clemson University): The position

  • relative to the goal line changes the set of options that

  • the running back has in terms of the direction he chooses to run.

  • HOLT: A second kinematic concept is velocity,

  • which describes both the direction and speed of the running back.

  • In the NFL, one way speed is measured is a player's time

  • in the 40-yard dash.

  • DEUCE McALLISTER (Former NFL Running Back): A long,

  • long time ago, almost right at ten years ago,

  • my 40-yard dash was 4.26.

  • HOLT: To help illustrate the concepts of kinematics,

  • Deuce McAllister, all-time leading rusher for the New

  • Orleans Saints, performed the 40-yard dash in front of a

  • high-speed Phantom camera.

  • McALLISTER: You want to stay low as possible while running the

  • 40, particularly the first 10-yards.

  • So it's literally like you're being shot out of a cannon.

  • HOLT: Using McAllister's personal best in the 40,

  • 4.26 seconds, it's easy to calculate his speed.

  • Divide the distance by the time to get his average speed --

  • 9.39 yards-per-second, or 28.17 feet-per-second.

  • To define the velocity, simply add a direction:

  • 28.17 feet-per-second, north.

  • SCHMITZ: When we talk about speed, we're talking about the magnitude of velocity.

  • And then its direction is dictated by where the running back goes.

  • HOLT: On the field, great speed is used to elude tacklers.

  • MARSHALL FAULK (Former NFL Running Back): When you have

  • speed and you have very good speed,

  • that five yard play for most backs becomes a 50-yard play.

  • HOLT: Also helpful is the ability to cut,

  • or suddenly change directions.

  • LOUSAKA POLITE (Miami Dolphins Running Back): That helps you make

  • moves against the defender, that helps you get free from being tackled.

  • HOLT: Beyond position and velocity,

  • the third kinematic concept is acceleration,

  • which describes how fast speed is changing.

  • McALLISTER: You never know when you may need to hit that button,

  • you know, per se, to accelerate at maximum speed.

  • HOLT: To understand acceleration,

  • consider again McAllister's 40-yard dash.

  • While his average speed is 28.17 feet-per-second,

  • his instantaneous speed varies.

  • He starts with zero speed and then increases his speed,

  • or accelerates, until he reaches a top speed -- let's say,

  • hypothetically, 31.5 feet-per-second.

  • If we know how long it takes McAllister to hit his top speed,

  • let's assume 1.2 seconds, then it's possible to calculate his

  • acceleration as the change in speed divided by the time.

  • SCHMITZ: Acceleration is the change in velocity per unit

  • time, which if we compare it to velocity was the change in

  • distance per unit time.

  • HOLT: In this case, 31.5 feet-per-second,

  • divided by 1.2 seconds, means that McAllister's acceleration

  • was 26.25 feet-per-second squared.

  • SCHMITZ: We want to reach our top velocity as quickly as possible.

  • Someone with low acceleration might take five yards to reach

  • top velocity, while someone with great acceleration might be able

  • to reach top velocity in half that distance.

  • HOLT: On the playing field, acceleration,

  • or the ability to reach top speed quickly,

  • may be a running back's most potent weapon.

  • FAULK: If you can accelerate, you're going to get to top speed

  • even if your top speed isn't as fast as the guy that's faster

  • than you, you're going to beat him to his top speed,

  • therefore you're going to be more successful than he is.

  • HOLT: Without kinematics and its concepts of position,

  • velocity and acceleration, NFL running backs would be easy prey,

  • and football, itself, wouldn't be nearly as fun to watch.

LESTER HOLT, reporting: From big and bulldozing,

Subtitles and vocabulary

Operation of videos Adjust the video here to display the subtitles

B1 US holt speed velocity acceleration nfl running

Kinematics - Science of NFL Football

  • 20 0
    Jack posted on 2019/07/30
Video vocabulary