Fourth and nineteen, folks, they've gotta have a play as time's ticking away
第四次进攻机会，19码线，各位，随着时间的流逝，他们要对决了，
because they've got to stay in this ball game, they've got to win.
因为他们不想出局，他们一定要赢。
They come out lined up in the empty set, three receivers to the right, two to the left.
他们排成一条直线，三个接球员来到右边，两个来到左边。
Defense looks like they're gonna to man up with no safety.
防守方似乎不会让他们安全通过。
This is the exact offensive match-up that they want: the best receiver lined up against the linebacker.
这完全是他们要的配合：最好的接球员对上线卫球员。
Quarterback steps back to receive the ball, five yards deep in the gun.
四分卫后退接到球，距端区有5码的距离。
He takes a snap, drops three steps, he plants his back foot, he's looking for an opening.
他将球发出，往后退三步，后脚稳住，他在寻找一个机会。
There's a blitz coming off the edge!
边线那边有一个闪电突袭出现了！
He steps up to avoid the rush. He's looking down field.
他向前一步避免此次攻击。他向下看着场地。
He's got the inside receiver making a cut. He's got a step on the linebacker.
里面的接球员切了进来。他跑到线卫的位置。
Quarterback has a beat on it. He lets the ball go, it's in the air!
对方的四分卫要将他放倒。他把球抛向远方，球在空中飞！
Receiver is out in front of the defender. He's got it beat!
接球员跑到了防守者的前面。他要拿到球！
He's out in front, racing for the ball! It's coming down!
他跑到了前面，冲向球！球正在下落！
He cradles it at the fifteen! He's at the ten, five! Touchdown! Unbelievable play!
他在15码处接住了球！他现在在10码，5码！达阵！难以置信的一球！
Now, wait a minute. Of course, it's believable, it's physics, specifically the differences between scalars and vectors.
现在，等一下。当然，这是可信的，这是物理学，具体的说是标量和矢量的区别。
So, let's just see that replay.
那么，让我们看下回放。
"Quarterback steps back to receive the ball, five yards deep in the gun." Stop.
“四分卫向后退接到了球，距端区有5码的距离。”停。
See, measurements are defined as two different quantities.
看，测量值被定义为两个不同的量。
Scalars are measurements with only numbers, and vectors are measurements with direction.
标量仅用一个数字度量，而矢量还需要方向。
For example, when that quarterback takes the snap, he's five yards away, but from where?
举个例子，当四分卫发球时，他退了5码远，可是是从哪里呢？
Back from the line of scrimmage, so the five yards by itself is a scalar quantity.
是从攻防线向后，因此5码本身是一个标量。
When you add a direction, like five yards deep, it becomes a vector quantity.
当你增加一个方向后，比如向远端5码，它就成为了一个矢量。
Five yards - scalar, five yards deep - vector. OK, go ahead.
5码--标量。向远端5码--矢量。好的，继续。
"He takes a snap, drops three steps. He plants his back foot, he's looking for an opening.
“他将球发出，往后退三步，后脚稳住，他在寻找一个机会。
There's a blitz coming off the edge! He steps up to avoid the rush." Whoa!
边线那边有一个闪电突袭出现了！他向前一步避免此次攻击。”停止！
Here's a difference between distance and displacement.
距离和位移之间也有区别。
Distance is a measurement without identifying where you moved. It's a scalar quantity.
距离是一个没有标识你从哪里移动的量度。它是一个标量。
When the quarterback makes a three-step drop, he moves about three yards back.
当四分卫往后退三步，他大概移动了三码。

When he moves about another three yards forward, when he steps up into the pocket,
当他又往前移动了三码，他站到了保护圈里，
so that quarterback moves a total distance of six yards. That's a distance, that's a scalar.
这样四分卫移动的总距离为六码。这是距离，是一个标量。
Now, displacement is a vector quantity, describing about how far out of place the object is.
而位移则是一个矢量，描述一个物体对于同一个位置移动了多远。
So the quarterback dropped back three yards and then moved back forward three yards,
这样，四分卫向后3码，然后向前移回3码，
he's in the exact same place where he started. So, his displacement is zero yards.
他恰好又回到了开始的位置。这样，他的位移是0码。
Distance - six yards, displacement - zero yards.
距离是六码，位移则是0码。
So, let's look at what happened next.
那么让我们看看接下来发生了什么。
"Quarterback has a beat on it, he let's the ball go! It's in the air!
“对方的四分卫要将他放倒。他把球抛向远方，球在空中飞！
Receiver is out in front of the defender." Stop.
接球员跑到了防守者的前面。”停。
So, here's speed and velocity, but let's just do one thing at a time.
接着，速率和速度出现了，不过让我们一个一个来说。
So, speed is measurement without direction, it's a scalar quantity.
速率是一种没有方向的度量，它是一个标量。
Velocity is a vector quantity. It is that object's speed, but with a direction of motion.
速度则是一个矢量。他是指具有运动方向的物体的速率。
So the receiver accelerates away, gaining both speed and distance.
所以，接球员加速奔跑，同时产生了速率和距离。
This takes the receiver 5 seconds to run those 50 yards.
接球员总共花了五秒，跑了五十码。
So his average speed, in any given time, is 10 yards/second.
这样他的平均速率，在任何给定时间，是10码/秒。
The linebacker tries to keep up, but his overall speed is slower,
线卫努力去阻止他，可是他的整体速率要慢一些，
he only goes 35 yards in those 5 seconds, so his average speed is only 7 yards/second.
他在这5秒钟仅仅跑了35码，于是他的平均速率仅是7码/秒。
They're both traveling in a forward direction, so their velocity is also positive.
他们都在以一个向前的方向移动，所以他们的速度都是正的。
You can't go from resting to your peak speed immediately.
你不能立刻从静止达到最高速率。
You've got to build up to it. This is acceleration.
你需要逐渐增加速率。这是加速度。
At first the linebacker can keep up with that receiver, but eventually the faster receiver pulls away.
一开始线卫可以紧跟接球员，可是最终更快的接球员成功脱身了。
That's acceleration, the change in speed over time.
加速度就是速率的变化除以时间。
Acceleration is a vector quantity. It describes a rate at which an object changes velocity.
加速度是一个矢量。它是用来描述一个物体速度变化的比率。
Like velocity, acceleration is a vector. It happens in a direction.
像速度一样，加速度是矢量。它在方向中发生。
So let's just look at that play just one more time.
让我们再看一次比赛的回放。
"Quarterback steps back to receive the ball, five yards deep in the gun." Vector!
“四分卫向后退接到了球，距端区有5码的距离。”矢量！
"He takes a snap, drops three steps, he plants his back foot. He's looking for an opening.
“他将球发出，往后退三步，后脚稳住，他在寻找一个机会。
There's a blitz coming off the edge! He steps up to avoid the rush." Displacement!
边线那边有一个闪电突袭出现了！他向前一步避免此次攻击。”位移！
"He's got the inside receiver making a cut. He's got a step on the linebacker.
“里面的接球员切了进来。他跑到线卫的位置。
The quarterback has a beat on it. He let's the ball go! It's in the air!
对方的四分卫要将他放倒。他把球抛向远方，球在空中飞！
Receiver is out in front of the defender!" Velocity!
接球员跑到了防守者的前面。”速度！
"He's got it beat! He's out in front, racing for the ball! It's coming down!
他要拿到球！他跑到了前面，冲向球！球正在下落！
He cradles it at the fifteen, he's at the ten, five!" Acceleration!
他在15码处接住了球！他现在在10码，5码！”加速度！
"Touchdown! Unbelievable play! That was a great play as time expired,
“达阵！难以置信的一球！时间到时，这是一场精彩的比赛，
resulting in the touchdown and ultimately the win and pure effort." And pure science.
达阵并最终获得了胜利，纯粹的努力。”以及纯粹的科学。