Football physics: The "impossible" free kick - Erez Garty
-
0:07 - 0:11In 1997,
in a game between France and Brazil, -
0:11 - 0:14a young Brazilian player
named Roberto Carlos -
0:14 - 0:18set up for a 35 meter free kick.
-
0:18 - 0:20With no direct line to the goal,
-
0:20 - 0:24Carlos decided to attempt
the seemingly impossible. -
0:24 - 0:27His kick sent the ball flying
wide of the players, -
0:27 - 0:31but just before going out of bounds,
it hooked to the left -
0:31 - 0:33and soared into the goal.
-
0:33 - 0:36According to Newton's first law of motion,
-
0:36 - 0:39an object will move
in the same direction and velocity -
0:39 - 0:42until a force is applied on it.
-
0:42 - 0:46When Carlos kicked the ball,
he gave it direction and velocity, -
0:46 - 0:49but what force made the ball swerve
-
0:49 - 0:54and score one of the most magnificent
goals in the history of the sport? -
0:54 - 0:56The trick was in the spin.
-
0:56 - 1:00Carlos placed his kick
at the lower right corner of the ball, -
1:00 - 1:05sending it high and to the right,
but also rotating around its axis. -
1:05 - 1:08The ball started its flight
in an apparently direct route, -
1:08 - 1:12with air flowing on both sides
and slowing it down. -
1:12 - 1:17On one side, the air moved in the opposite
direction to the ball's spin, -
1:17 - 1:19causing increased pressure,
-
1:19 - 1:23while on the other side, the air moved
in the same direction as the spin, -
1:23 - 1:26creating an area of lower pressure.
-
1:26 - 1:31That difference made the ball curve
towards the lower pressure zone. -
1:31 - 1:34This phenomenon is called
the Magnus effect. -
1:34 - 1:38This type of kick,
often referred to as a banana kick, -
1:38 - 1:40is attempted regularly,
-
1:40 - 1:44and it is one of the elements
that makes the beautiful game beautiful. -
1:44 - 1:46But curving the ball
with the precision needed -
1:46 - 1:51to both bend around the wall
and back into the goal is difficult. -
1:51 - 1:53Too high and it soars over the goal.
-
1:53 - 1:57Too low and it hits the ground
before curving. -
1:57 - 1:59Too wide and it never reaches the goal.
-
1:59 - 2:03Not wide enough
and the defenders intercept it. -
2:03 - 2:06Too slow and it hooks too early,
or not at all. -
2:06 - 2:09Too fast and it hooks too late.
-
2:09 - 2:11The same physics make it possible
-
2:11 - 2:14to score another
apparently impossible goal, -
2:14 - 2:18an unassisted corner kick.
-
2:18 - 2:21The Magnus effect was first documented
by Sir Isaac Newton -
2:21 - 2:26after he noticed it while playing a game
of tennis back in 1670. -
2:26 - 2:30It also applies to golf balls,
frisbees and baseballs. -
2:30 - 2:33In every case, the same thing happens.
-
2:33 - 2:38The ball's spin creates a pressure
differential in the surrounding air flow -
2:38 - 2:41that curves it
in the direction of the spin. -
2:41 - 2:42And here's a question.
-
2:42 - 2:44Could you theoretically
kick a ball hard enough -
2:44 - 2:48to make it boomerang
all the way around back to you? -
2:48 - 2:50Sadly, no.
-
2:50 - 2:53Even if the ball didn't
disintegrate on impact, -
2:53 - 2:54or hit any obstacles,
-
2:54 - 2:56as the air slowed it,
-
2:56 - 2:59the angle of its deflection
would increase, -
2:59 - 3:03causing it to spiral into smaller
and smaller circles -
3:03 - 3:05until finally stopping.
-
3:05 - 3:07And just to get that spiral,
-
3:07 - 3:11you'd have to make the ball spin
over 15 times faster -
3:11 - 3:14than Carlos's immortal kick.
-
3:14 - 3:16So good luck with that.
- Title:
- Football physics: The "impossible" free kick - Erez Garty
- Speaker:
- Erez Garty
- Description:
-
View full lesson: http://ed.ted.com/lessons/football-physics-the-impossible-free-kick-erez-garty
In 1997, Brazilian football player Roberto Carlos set up for a 35 meter free kick with no direct line to the goal. Carlos’s shot sent the ball flying wide of the players, but just before going out of bounds it hooked to the left and soared into the net. How did he do it? Erez Garty describes the physics behind one of the most magnificent goals in the history of football.
Lesson by Erez Garty, animation by TOGETHER.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TED-Ed
- Duration:
- 03:33
Jessica Ruby approved English subtitles for Football physics: The "impossible" free kick | ||
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Jessica Ruby accepted English subtitles for Football physics: The "impossible" free kick | ||
Jessica Ruby edited English subtitles for Football physics: The "impossible" free kick | ||
Jessica Ruby edited English subtitles for Football physics: The "impossible" free kick | ||
Jennifer Cody edited English subtitles for Football physics: The "impossible" free kick | ||
Jennifer Cody edited English subtitles for Football physics: The "impossible" free kick |