An athlete uses physics to shatter world records - Asaf Bar-Yosef

一个用物理征服世界纪录的运动员 - Asaf Bar-Yosef

翻译人员: Minji Seo 校对人员: Thunder Song

In the early 1960s,

1960 年代初

Dick Fosbury tried his hand at almost every sport,

Dick Fosbury 遍尝各种体育项目，

but never excelled at anything,

却始终没在哪一项出头

until, at the age of 16, he turned to the high jump.

直到 16 岁那年，他试了跳高运动

But when he couldn't compete against

开始，当他无法击败

the strong athletes at his college

学院中的优异选手

using the standard high jump techniques of the time,

使用当时的标准式跳法，

Fosbury tried to jump a different way: backwards.

Fosbury 尝试与众不同的方法：背跃

不像一般选手般面向杆子翻转

Instead of jumping with his face towards the bar,

bringing each leg over in the

（两脚依次翻过

的剪刀式（straddle）跳法）

traditional straddle method,

he jumped with his back towards the bar.

而Fosbury 背向横杆越过

Fosbury improved his record by over half a foot,

如此，他的成绩跃进了 15.24 公分，

and left his coaches amazed

教练也折服

by this strange new style of high jumping.

在这诡异的新跳法面前。

During the next few years,

往后数年，

Fosbury perfected his high jump style,

Fosbury 完成了他的背跃绝技，

won the U.S. National trials,

通过了美国的国手选拔，

and assured his place in the 1968 Olympics in Mexico.

并在 1968 年墨西哥城奥运会 挣得了历史定位

In the Olympic Games, Fosbury amazed the world

在奥运会上，Fosbury 惊艳了全世界

with his new technique, winning a gold metal

并以他的独门绝活一举夺下金牌，

with an Olympic record leap of 2.24 meters.

还顺便推进了奥委会记录，由 2.22 到 2.24 公尺。

By the next Olympic Games,

于是下一届奥运会中

almost all of the competing of high jumpers

几乎所有选手都使用了

had adopted what came to be known as

新的背跃式跳法

the Fosbury Flop.

Fosbury 的鱼跃 （一名记者，认为以弯曲的背部坠落软垫， 像上岸的鱼乱跳 ）

What's the secret behind the technique?

这个招式背后的秘密是什么？

It lies in a physics concept

答案藏在一个物理概念里：

called the center of mass.

称为质量中心（质心）。

For every object,

对任何物体

we can locate the average position of all of its mass

我们都可以藉由

考虑物体质量 在三维空间中的分布情形

by taking into account how the mass

is spread around the object.

来确定其质量的平均位置。

For instance, the center of mass

例如，一个扁平、长方形、

of a flat, rectangular object of uniform density

密度均一的物体，其质心

会落在两对角线的交点，

will be in the intersection of both diagonals,

in equal distance from each corner.

与其它角落等距。

We can find the center of mass for other objects

对于别的物体 我们可以透过类似的方法

by similar calculations,

来寻找其质量中心。

or by finding the object's balancing point,

或是直接找物体的平衡点，

which lies right underneath its center of mass.

平衡点会落在质心的正下方。

Try balancing a broom by holding it

试试用双手托着扫把的柄，

and slowly bringing your hands together until they meet.

并轻轻用力让两手往内滑动，直到手掌合十。

This balancing point lies right underneath

这时平衡点就在扫把的质心下

the broom's center of mass.

这时平衡点就在扫把的质心下

We humans also have a center of mass.

人体自然也有一个质心。

When most people stand up,

大多数人站直时，

their center of mass is around the belly,

质心位在肚脐附近。

but what happens to your center of mass

当你举起双手，

when you lift your hands in the air?

你的质心会有啥变化？

Your center of mass moves upwards.

质心会向上移动

It moves all the time as you move through the day,

在你一天的活动中，你的质心据你的姿势

based on how your body is positioned.

四处动来动去。

It can even move outside of your body.

甚至有些姿势，会让 你的质心位在身体的外部。

When you bend forward, your center of mass

例如腰向前仰

is located below your bent belly

质心会在你的腹部下方，

in a place where there is no mass at all.

即使那一点空无一物。

Weird to think about, but that's the average position

想起来似乎怪怪的，但它确实是这时

你身体所有部分的平均位置。

of all your mass.

Many objects' center of mass

还有许多物品的质心

are outside their bodies.

处在物品外面，

Think of doughnuts or boomerangs.

例子有甜甜圈，和回飞镖。

Now look at the Fosbury Flop, and follow the position

现在我们能回来看 Fosbury 的后跃了，

注意动作中运动员的质心位置。

of the center of mass of the jumper.

The jumper runs very fast,

选手首先高速助跑，

so he can divert his horizontal velocity

将一部分的水平速度

to vertical velocity, and jumps.

转移成垂直起跳的速度，于是跳！

Wait for it...there.

留神......就这儿。

Look at the jumper's center of mass

注意到选手身体往后弓起时

as his body bends backward.

质心所在位置吗？

It's below the bar.

事实上它还在横杆之下！

That is the secret behind the jump.

这就是背跃绝技的奥秘。

With the old, pre-Fosbury techniques,

在 Fosbury 登场以前，跳高的技术

the jumper had to apply enough force

全仰赖选手拼命使劲

to lift his center of mass above the bar

为了将他们的质心抬到杆子以上数吋

by a few inches in order to clear it.

才能避免越过时把杆子撞掉。

The Fosbury Flopper doesn't have to do that.

但背跃式跳法回避了这个瓶颈。

The genius of the Fosbury Flop is that the jumper

Fosbury 方法的天才之处在于，

can apply the same amount of force,

选手花同样力气，其质心和原本一样高，

but raise his body much higher than before.

身体却能处在更高位。

That means he can raise the bar so high

这代表杆子能继续往上摆，

that even when his center of mass

即使质心的高度再也提升不了

can't go any higher, his arching body can.

弯曲的身体却可以由上方跳过去。

Fosbury's technique brought

Fosbury 的新招式让跳高的

the high jump to new heights

世界纪录连创新高，

原理是尽量弯曲身体，

by splitting the jumper's body

away from his center of mass,

使选手的质心离身体越远越好，

giving it that much more room

因此有更多空间能运用于

to clear higher and higher bars.

闪过不断加高的横杆。

So the Fosbury Flop may be sports history's

因此可以说，Fosbury 绝技是运动史上

only great leap forward,

的一次向前大飞跃，

that is also a great leap backward.

并且是向后飞跃。