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  • In 1997, in a game between France and Brazil,

  • a young Brazilian player named Roberto Carlos

  • set up for a 35 meter free kick.

  • With no direct line to the goal,

  • Carlos decided to attempt the seemingly impossible.

  • His kick sent the ball flying wide of the players,

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

  • and soared into the goal.

  • According to Newton's first law of motion,

  • an object will move in the same direction and velocity

  • until a force is applied on it.

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

  • but what force made the ball swerve

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

  • The trick was in the spin.

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

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

  • The ball started its flight in an apparently direct route,

  • with air flowing on both sides and slowing it down.

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

  • causing increased pressure,

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

  • creating an area of lower pressure.

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

  • This phenomenon is called the Magnus effect.

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

  • is attempted regularly,

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

  • But curving the ball with the precision needed

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

  • Too high and it soars over the goal.

  • Too low and it hits the ground before curving.

  • Too wide and it never reaches the goal.

  • Not wide enough and the defenders intercept it.

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

  • Too fast and it hooks too late.

  • The same physics make it possible

  • to score another apparently impossible goal,

  • an unassisted corner kick.

  • The Magnus effect was first documented by Sir Isaac Newton

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

  • It also applies to golf balls, frisbees and baseballs.

  • In every case, the same thing happens.

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

  • that curves it in the direction of the spin.

  • And here's a question.

  • Could you theoretically kick a ball hard enough

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

  • Sadly, no.

  • Even if the ball didn't disintegrate on impact,

  • or hit any obstacles,

  • as the air slowed it,

  • the angle of its deflection would increase,

  • causing it to spiral into smaller and smaller circles

  • until finally stopping.

  • And just to get that spiral,

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

  • than Carlos's immortal kick.

  • So good luck with that.

In 1997, in a game between France and Brazil,

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B1 TED-Ed ball kick carlos spin goal

【TED-Ed】Football physics: The "impossible" free kick - Erez Garty

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    稲葉白兎 posted on 2015/06/17
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