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

Fizika fudbala: "nemogući" slobodan udarac - Erez Garti (Erez Garty)

Prevodilac: Mile Živković Lektor: Milenka Okuka

In 1997, in a game between France and Brazil,

Godine 1997, na utakmici između Francuske i Brazila,

a young Brazilian player named Roberto Carlos

mladi igrač Brazila Roberto Karlos

set up for a 35 meter free kick.

nameštao se za slobodan udarac sa 35 metara.

With no direct line to the goal,

Bez direktne linije do gola,

Carlos decided to attempt the seemingly impossible.

Karlos je odlučio da pokuša naizgled neverovatno.

His kick sent the ball flying wide of the players,

Njegov udarac poslao je loptu daleko od igrača,

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

ali tik pred izlazak iz terena, ona je skrenula nalevo

and soared into the goal.

i uletela u gol.

According to Newton's first law of motion,

Po Njutnovom prvom zakonu kretanja,

an object will move in the same direction and velocity

objekat će se kretati u istom pravcu i po istoj brzini

until a force is applied on it.

dok se na njega ne primeni sila.

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

Kada je Karlos šutnuo loptu, odredio joj je pravac i brzinu,

but what force made the ball swerve

ali koja sila je naterala loptu da skrene

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

i zada jedan od najveličanstvenijih golova u istoriji ovog sporta?

The trick was in the spin.

Trik je bio u spinu.

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

Karlos je loptu šutnuo u donjem desnom uglu,

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

poslavši je visoko nadesno, ali i tako da se okreće oko svoje ose.

The ball started its flight in an apparently direct route,

Lopta je sa letom počela na naizgled pravoj putanji

with air flowing on both sides and slowing it down.

i vazduh je strujao sa obe njene strane i usporavao je.

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

Sa jedne strane, vazduh se kretao u suprotnom pravcu od spina lopte,

causing increased pressure,

tako dovodeći do povećanog pritiska

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

dok je sa druge strane vazduh koji se kretao u pravcu spina

creating an area of lower pressure.

stvarao prostor nižeg pritiska.

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

Ta razlika naterala je loptu da skrene ka zoni nižeg pritiska.

This phenomenon is called the Magnus effect.

Ova pojava naziva se Magnusovim efektom.

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

Ova vrsta udarca, koja se često naziva banana udarcem,

is attempted regularly,

često se pokušava izvesti

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

i jedan je od elemenata koji prelepu igru čini prelepom.

But curving the ball with the precision needed

Ali skretanje lopte sa neophodnom preciznošću

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

da se zaobiđe zid i da se ona vrati u gol je komplikovano.

Too high and it soars over the goal.

Previsoko i ona ode iznad gola.

Too low and it hits the ground before curving.

Prenisko i ona udara u tlo pre nego što skrene.

Too wide and it never reaches the goal.

Preširoko i nikad neće stići do gola.

Not wide enough and the defenders intercept it.

Nedovoljno široko i igrači odbrane će je presresti.

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

Presporo i skrenuće prerano ili neće skrenuti uopšte.

Too fast and it hooks too late.

Prebrzo i skrenuće prekasno.

The same physics make it possible

Ista vrsta fizike omogućava

to score another apparently impossible goal,

postizanje još jednog naizgled nemogućeg gola,

an unassisted corner kick.

neasistiranog udarca iz kornera.

The Magnus effect was first documented by Sir Isaac Newton

Ser Ajzak Njutn je prvi put zabeležio Magnusov efekat

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

nakon što ga je primetio na partiji tenisa 1670.

It also applies to golf balls, frisbees and baseballs.

Takođe je primenjiv na loptice za golf, bejzbol i na frizbije.

In every case, the same thing happens.

U svakom od ovih slučajeva dešava se isto.

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

Spin lopte stvara pritisak diferencijalan u odnosu na okolni tok vazduha

that curves it in the direction of the spin.

koji skreće loptu u pravcu spina.

And here's a question.

Evo pitanja.

Could you theoretically kick a ball hard enough

Da li biste teoretski mogli da šutnete loptu dovoljno jako

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

da se vrati skroz do vas poput bumeranga?

Sadly, no.

Nažalost, ne.

Even if the ball didn't disintegrate on impact,

Čak i kada se lopta ne bi raspala pri udarcu,

or hit any obstacles,

ili se susrela s nekom preprekom,

as the air slowed it,

kako bi je vazduh usporavao,

the angle of its deflection would increase,

ugao skretanja bi se povećavao

causing it to spiral into smaller and smaller circles

zbog čega bi kružila u sve manjim krugovima

until finally stopping.

dok konačno ne bi stala.

And just to get that spiral,

A samo da biste dobili to kruženje,

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

morali biste da dovedete loptu do spina 15 puta bržeg

than Carlos's immortal kick.

od Karlosovog besmrtnog šuta.

So good luck with that.

Stoga, srećno s time.