National Geographic has the story on the latest World Cup soccer ball design and how it will impact the game from a physics perspective.
Every year the newest version of the World Cup soccer ball causes a stir. Now physicists have put those balls to the test, to see just how well they fly.
World Cup soccer balls used to be not much different from regular soccer balls—32 leather panels stitched together by hand. But the balls used in World Cup tournaments have been distinctive since 2006, when Adidas unveiled the Teamgeist, made of just 14 panels that had been glued together rather than stitched. The company has been introducing new World Cup balls ever since: the eight-panel Jabulani ball in 2010 and for the 2014 games—which begin on June 12 in São Paulo, Brazil—the six-panel Brazuca.
Will this change in design make a difference in the game? That’s what Sungchan Hong and his colleagues at the University of Tsukuba wanted to find out. Making use of some soccer balls, a wind tunnel, and a robot, they found, according to today’s Scientific Reports, that a ball’s construction really does affect how it flies through the air.
What’s most relevant in a ball’s movement is drag, a force that makes it dip and curve in unexpected ways. The smoother the ball, the greater the drag at higher speeds—and with fewer panels that are glued rather than stitched together, the World Cup balls have been getting increasingly smoother.
Which is why this year the Brazuca ball is covered in little nubs—an attempt to cut down on the so-called knuckling effect, which causes the ball to move unpredictably through the air like a knuckleball in baseball.
In the wind tunnel, Hong found, the direction in which the ball is pointed, and thereby the direction in which the panels are oriented, changes the drag. This was a problem for the 8-panel Jabulani ball and the 14-panel Teamgeist ball, each of which traveled more unpredictably than a regular soccer ball, curving more or less depending on which way it was oriented.
But the new 6-panel Brazuca seems to be far more reliable, showing very little difference in behavior no matter how it’s rotated. This is likely due to the way the panels of the Brazuca are arranged, along with the rough surface Adidas added to cut down on the drag.