Football physics: The "impossible" free kick - Erez Garty

足球中的物理：不可思议的“任意球” - Erez Garty

翻译人员: Zongzhen Yang 校对人员: Cissy Yun

In 1997, in a game between France and Brazil,

1997年，在一场法国与巴西之间的比赛中

a young Brazilian player named Roberto Carlos

一名叫Robert Carlos的年轻巴西球员

set up for a 35 meter free kick.

从35米外发了任意球

With no direct line to the goal,

没有任何通向球门的直线

Carlos decided to attempt the seemingly impossible.

Carlos的尝试看起来是不可能

His kick sent the ball flying wide of the players,

他的射门让球飞过球员，

but just before going out of bounds, it hooked to the left

但是就当球要出界时，它向左勾

and soared into the goal.

然后进门

According to Newton's first law of motion,

根据牛顿的第一定律

an object will move in the same direction and velocity

一个物体会以同样的方向和矢量移动

until a force is applied on it.

除非一个力被施加

When Carlos kicked the ball, he gave it direction and velocity,

但Carlos踢球时，他已经给球速度和矢量了

but what force made the ball swerve

但是是什么力让球改变方向

and score one of the most magnificent goals in the history of the sport?

然后成为运动史以来最伟大的进球之一？

The trick was in the spin.

诀窍是旋转

Carlos placed his kick at the lower right corner of the ball,

Carlos从右下方踢球

sending it high and to the right, but also rotating around its axis.

让球边绕轴心旋转，边向右侧高飞

The ball started its flight in an apparently direct route,

球从一个明显的直线起飞

with air flowing on both sides and slowing it down.

空气飞过两边使其变慢

On one side, the air moved in the opposite direction to the ball's spin,

在一边，空气以球转的反方向旋转

causing increased pressure,

导致压力上升

while on the other side, the air moved in the same direction as the spin,

然而在另一边，空气以与球相同的方向旋转

creating an area of lower pressure.

产生一部分低压区

That difference made the ball curve towards the lower pressure zone.

这个差异，使球向低压区弯曲

This phenomenon is called the Magnus effect.

这个现象叫做马格纳斯效应

This type of kick, often referred to as a banana kick,

这种踢球，也被叫做香蕉球

is attempted regularly,

被经常使用

and it is one of the elements that makes the beautiful game beautiful.

而且它会让一场精彩的比赛更加精彩

But curving the ball with the precision needed

但是香蕉球所需要的精准度

to both bend around the wall and back into the goal is difficult.

使其偏向墙然后进门，是非常困难的

Too high and it soars over the goal.

太高的话球会飞过球门

Too low and it hits the ground before curving.

太低的话会在旋转前击地

Too wide and it never reaches the goal.

角度太大的话会永远进不了球门

Not wide enough and the defenders intercept it.

角度不够大的话 防守者就可以拦截

Too slow and it hooks too early, or not at all.

太慢的话球会早转弯，甚至不转

Too fast and it hooks too late.

太快的话球会转的太晚

The same physics make it possible

同样的物理理论

to score another apparently impossible goal,

使一个看起来不可能，没有收到任何帮助的

an unassisted corner kick.

的角球进球

The Magnus effect was first documented by Sir Isaac Newton

马格纳斯效应最初是被伊萨克·牛顿所记录

after he noticed it while playing a game of tennis back in 1670.

在1670年，他打完一场网球后发现的

It also applies to golf balls, frisbees and baseballs.

这个原理同样适应于高尔夫球，飞碟和棒球

In every case, the same thing happens.

在每个情况下，同样的事情总是发生

The ball's spin creates a pressure differential in the surrounding air flow

球的旋转产生环绕的气流气压不等

that curves it in the direction of the spin.

从而导致球向其旋转

And here's a question.

又有一个问题了

Could you theoretically kick a ball hard enough

从理论上来讲，你可以将球使劲踢

to make it boomerang all the way around back to you?

足以让球转回你吗？

Sadly, no.

可惜的是，不行

Even if the ball didn't disintegrate on impact,

即使球没有在冲撞中解体

or hit any obstacles,

或者击中任何障碍物

as the air slowed it,

空气使其变慢

the angle of its deflection would increase,

偏转角会增加

causing it to spiral into smaller and smaller circles

使螺旋变成越来越小的圆

until finally stopping.

最终停止

And just to get that spiral,

只是达到旋转

you'd have to make the ball spin over 15 times faster

你需要使球转的

than Carlos's immortal kick.

比Carlos不朽的进球快15倍

So good luck with that.

那祝你好运