June 30, 2010
World Cup Ball Analyzed By Scientists
Since being chosen for the World Cup, the Jabulani football has been criticized as being "rotten" and "unpredictable" by World Cup players.
Scientists have analyzed the controversial ball and have been puzzled over its allegedly erratic flight. Experts have concluded that the ball might be simply too round to fly straight.One problem that makes the ball capricious may be that "the stitches of the Jabulani are internal, so the ball resembles a perfect sphere," said Eric Berton, deputy director of the Institute of the Science of Movement in Marseille, France.
In most sports the balls have irregularities precisely to insure a more stable and controllable trajectory. The exposed seams are what make a ball spin, curve, fly straight.
"Because of the shape, the time of contact with the foot is reduced," Berton said. "As a consequence, it practically doesn't spin. The ball travels a little less far, and will have a floating and unpredictable trajectory, whether for a striker or a goalkeeper," he told AFP.
Kazuya Seo of Yamagata and Takeshi Asai University in Tsukuba conducted wind-tunnel testing on the machine-made Jabulani and found that the ball was close to a perfect sphere. They also found that it has a tendency to slow suddenly in mid-flight -- which doesn't fly well with footballers.
Australian scientist Derek Leinweber of Adelaide University concluded after a series of tests that the ball goes much faster and is more unpredictable than traditional balls.
"That means the goalkeeper can no longer really anticipate its trajectory," said Leinweber.
However, FIFA, upon unveiling the Jabulani ball, said it "allows for maximum control, stable flight and perfect grip under all conditions."
The ball is constructed of eight thermally-bonded polyurethane panels, and is virtually waterproof.
"There are strict FIFA guidelines on the ball (weight, size, bounce depending on what the temperature is)," commented the German maker Adidas. "Not only does our ball fulfill all these conditions but in fact they go beyond them."
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