The physics behind a World Cup soccer ball

A new soccer ball, the Brazuca, has been created for the 2014 FIFA World Cup. Physics experts from the University of Adelaide have described it is a ‘keepers' ball’, in contrast with the 2010 ball, the Jabulani.

Professor Derek Leinweber, from the university’s School of Chemistry and Physics, said the Jabulani ball was particularly smooth, with small grooves and ridges across its surface. “That meant the ball had to be moving much faster before the airflow around the ball changed from smooth to turbulent,” he said. “As this shift to turbulent airflow occurred at high speeds, the ball could make some pretty erratic movements on the way to the net.”

This resulted in the Jabulani being compared to a beach ball, with its erratic flight path often fooling goalkeepers. PhD candidate Adrian Kiratidis said this issue has been resolved by making the Brazuka “an aerodynamically rougher ball” with longer and deeper seams.

The researchers have been investigating the likely performance of the new ball by matching up the physics of airflow with available wind tunnel data and video of the ball’s movement. Professor Leinweber said the deeper grooves of the Brazuca cause it to hit turbulent airflow at lower speeds, “with the result that the ball is much more predictable”.

“Keepers facing players of the calibre of Messi, Cristiano Ronaldo or Neymar are going to be glad that it’s Brazuca coming at them rather than Jabulani,” he said.

Kiratidis will explain the science behind World Cup soccer balls at a free public lecture on 12 June at 6.30 pm. For more information on the event, click here.

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