Name: Kinematics - Science of NFL Football
Uploaded: 2019-07-30T09:19:01.000Z
Duration: 5 min 25 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

LESTER HOLT, reporting: From big and bulldozing,

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

Modal verbs - B1

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

kinematics, the branch of classical mechanics

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 defines location within a space,

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

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

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

long time ago, almost right at ten years ago,

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

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

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:

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

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

HOLT: Also helpful is the ability to cut,

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

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

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.

consider again McAllister's 40-yard dash.

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

He starts with zero speed and then increases his speed,

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

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

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

divided by 1.2 seconds, means that McAllister's acceleration

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.