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足球中的物理——不可思议的任意球 – 译学馆
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足球中的物理——不可思议的任意球

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

在1997年 一场法国队与巴西队的足球比赛中
In 1997, in a game between France and Brazil,
一个叫罗伯托•卡洛斯的年轻巴西球员
a young Brazilian player named Roberto Carlos
准备主罚一个距离球门35米的任意球
set up for a 35 meter free kick.
没有直接取得进球的途径
With no direct line to the goal,
卡洛斯决定尝试一下看起来不可能的选择
Carlos decided to attempt the seemingly impossible.
他的射门让球绕人墙很远
His kick sent the ball flying wide of the players,
但在出界前又急速向左转
but just before going out of bounds, it hooked to the left
骤然上升并取得进球
and soared into the goal.
通过牛顿运动学第一定律
According to Newton’s first law of motion,
一个物体会沿同向匀速运动
an object will move in the same direction and velocity
直到一个力作用在它上面
until a force is applied on it.
当卡洛斯踢出球时 他给了球方向和速度
When Carlos kicked the ball, he gave it direction and velocity,
但是什么力让足球突然转弯呢
but what force made the ball swerve
并且让这个进球在足球这项运动的历史上成为最精彩的一个之一
and score one of the most magnificent goals in the history of the sport?
窍门在于旋转
The trick was in the spin.
卡洛斯在球的右下方发力踢出球
Carlos placed his kick at the lower right corner of the ball,
让它高高地飞向右边 同时绕着轴旋转
sending it high and to the right, but also rotating around its axis.
足球开始以表面上清晰的路径飞行
The ball started its flight in an apparently direct route,
同时空气在球的两侧流动使它减速
with air flowing on both sides and slowing it down.
一方面 空气加快了球的相反方向的旋转
On one side, the air moved in the opposite direction to the ball’s spin,
从而增加压力
causing increased pressure,
另一方面 空气加快了同向的旋转
while on the other side, the air moved in the same direction as the spin,
创造出一片低压的区域
creating an area of lower pressure.
这样的区别让球在通过低压区时划出一道曲线
That difference made the ball curve towards the lower pressure zone.
这个现象被称为马格努斯效应
This phenomenon is called the Magnus effect.
这种踢球方式 经常被归类为香蕉球
This type of kick, often referred to as a banana kick,
被球员们经常尝试
is attempted regularly,
这是让足球比赛更加精彩的元素之一
and it is one of the elements that makes the beautiful game beautiful.
但让球划出弧线需要十分精确
But curving the ball with the precision needed
同时绕过人墙 并进球得分是十分困难的
to both bend around the wall and back into the goal is difficult.
踢的太高会高出横梁
Too high and it soars over the goal.
踢得太低球会在划出弧线前触地
Too low and it hits the ground before curving.
踢的太偏会让球远离球门
Too wide and it never reaches the goal.
绕的不够多会被防守队员拦截
Not wide enough and the defenders intercept it.
球速太慢会太早的划出弧线 或者没有弧线
Too slow and it hooks too early, or not at all.
球速太快就会过晚地划出弧线
Too fast and it hooks too late.
同样的物理学原理让另一种看起来不可能的进球
The same physics make it possible
变得可能
to score another apparently impossible goal,
角球直接射门得分
an unassisted corner kick.
马格努斯效应被艾萨克•牛顿在1670年首先证明
The Magnus effect was first documented by Sir Isaac Newton
这是在他在打网球比赛时注意到的
after he noticed it while playing a game of tennis back in 1670.
这个效应也适用于高尔夫球 飞盘和棒球
It also applies to golf balls, frisbees and baseballs.
在每一个实例中 发生着相同的事
In every case, the same thing happens.
球的旋转制造出与周围的气流不同的压力
The ball’s spin creates a pressure differential in the surrounding air flow
让球沿旋转的方向划出弧线
that curves it in the direction of the spin.
那么这里有个问题
And here’s a question.
如果你足够用力地踢球
Could you theoretically kick a ball hard enough
理论上能不能让它沿着原路飞回来
to make it boomerang all the way around back to you?
不幸的是 不行
Sadly, no.
即使这个球没有被冲击力粉碎
Even if the ball didn’t disintegrate on impact,
或者撞到任何的障碍物
or hit any obstacles,
当空气使它减速
as the air slowed it,
偏差的角度将会增加
the angle of its deflection would increase,
使它绕着越来越小的圆转圈
causing it to spiral into smaller and smaller circles
直到最终停下来
until finally stopping.
为了得到这种螺旋状的旋转
And just to get that spiral,
你需要让球以卡洛斯的神仙球十五倍多的速度
you’d have to make the ball spin over 15 times faster
进行旋转
than Carlos’s immortal kick.
这要有多好的运气啊
So good luck with that.

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视频概述

看似神奇的任意球背后 是如此奇妙的物理学原理

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收集自网络

翻译译者

RayLiu

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WeiRan

视频来源

https://www.youtube.com/watch?v=m57cimnJ7fc

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