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July 2010 Issue
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World Cup ball proves unpredictable


Physics experts at the University of Adelaide have weighed into the debate about the controversial new soccer ball being used in the 2010 World Cup.

Called the Jabulani, the ball generated a lot of negative attention from players - especially goalkeepers - in the lead-up to the start of the World Cup.

Professor Derek Leinweber, Head of the School of Chemistry & Physics at the University of Adelaide, said the aerodynamics of the ball meant that it would play "harder and faster", bending more unpredictably than its predecessor.

Professor Leinweber has previously written about and lectured on the aerodynamics of cricket balls, golf balls and the 2006 World Cup soccer ball, the Teamgeist.

Along with student Adrian Kiratidis, who is studying for his Master of Philosophy (MPhil) in Physics, Professor Leinweber has been investigating the physics behind soccer balls and what that means for the Jabulani. Adrian is also a soccer enthusiast.

"The Jabulani is textured with small ridges and 'aero grooves' and represents a radical departure from the ultra-smooth Teamgeist ball, which was used in the last World Cup," said Professor Leinweber.

"While the governing body FIFA has strict regulations on the size and weight of the balls, they have no regulations about the outside surface of the balls.

"The Teamgeist was a big departure at the last World Cup. Because it was very smooth - much smoother than a regular soccer ball - it had a tendency to bend more than the conventional ball and drop more suddenly at the end of its trajectory.

"By comparison, the aerodynamic ridges on the Jabulani can create enough turbulence around the ball to sustain its flight longer, and be a faster, harder ball in play."

Professor Leinweber said the Jabulani would 'bend' more for the players than any ball previously encountered.

"Players are also discovering new opportunities to move the ball in erratic ways, alarming the world's best goalkeepers. By the time the ball reaches the goalkeeper, the Jabulani will have swerved and dipped, arriving with more power and energy than the Teamgeist."

University of Adelaide students have also put the new World Cup soccer ball to the test on the soccer field. Based on Professor Leinweber's theories, they have attempted to "bend" the Jabulani and have also kicked the Teamgeist and a regular soccer ball for comparison.

"The ease with which the spinning Jabulani bends is opening up new scoring opportunities. Already, bends around the goalkeeper and dips under the crossbar have figured prominently in the World Cup, with many goals scored from surprising places," Professor Leinweber said.

Story by David Ellis

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Physics Masters student Adrian Kiratidis with three different soccer balls  the Teamgeist, the <i>Jabulani</i> and a regular soccer ball
Photo by Matt Carty, courtesy of <i>The Advertiser</i>

Physics Masters student Adrian Kiratidis with three different soccer balls - the Teamgeist, the Jabulani and a regular soccer ball
Photo by Matt Carty, courtesy of The Advertiser

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