Monday, June 7, 2010

The Unpredictable World Cup Soccer Ball "Jabulani"

Can you feel it? The FIFA World Cup Soccer Finals produce an electricity unmatched by any other world sporting event with only the Summer Olympic Games being in contention.

To add to the excitement every 4 years since 1970, FIFA has introduced a new soccer ball for the World Cup tournament. As the World Cup nears the opening game on June 11, 2010, we once again hear the anguished cries of the forsaken goalkeepers in reference to this years Adidas "Jabulani" ball.

Every 4 years goalkeepers complain that the new balls flight path is more unpredictable. “Highly unpredictable when hit from long distances.” says Wendell, the Brazilian goalkeeper coach about the "Jabulani" ball. In 2006 England's goalkeeper Paul Robinson criticised the then World Cup Ball named "Teamgeist" for being too light and behaving unpredictably.
Sound familiar?

The "Jabulani" ball to be used at the World Cup hosted in South Africa, is made with 8 3D molded panels. This is fewer than the 2006 ball, made with 12 panels and of course far less than the original soccer ball made with numerous black and white panels that were stitched together. The "Jabulani" also has aero grooves, which are there to stabilize flight in the air and will provide grip in the wet for both strikers and goalkeepers. The ball is also said to be rounder than any previous soccer ball because of the 3D molded panels.

Time to use our video analysis to see what the fuss is all about. Take a look at a recent goal scored from a free kick by China's Deng Zhuoxiang against France on June 4th 2010.

Those of us who have watched football and particularly free kicks in the past will have seen this type of thing before. Watch as the ball moves toward the goalkeepers left at the start of the flight and then swerves right after passing the wall.

The French goalkeeper Lloris moves left to cover the shot and then has to change direction to his right as the ball swerves past him. Great free kick, whether Deng intended it or not.

Now take a look at a goal by Danny Rose of Tottenham Hotspurs against Arsenal in February 2010.

This goal is scored with the old "Teamgeist" ball and the movement through the air can be considered as dramatic as that for Deng's goal.

The goalkeepers might not like it very much but each time a new ball is created it does improve the control that the strikers have over the ball.

The top spin that Nadal uses to destroy opponents in tennis, the curve ball thrown in baseball and the reverse swing in cricket are all examples of so called "unpredictable" behaviour of a round ball. The fact is that with a more better ball, a player that can create enough speed and spin in a specific direction, can use physics to make the soccer ball move around "unpredictably" for the goalkeeper.

To measure the movement on a perfect round ball lets assume that a free kick is taken 30 meters out and hit at a good 30 meters per second or around 70 mph with a spin of about 10 revolutions per second. With this information and knowledge of the balls coefficient of drag we could calculate the distance the ball would "move" swerve off course at about 4 meters or 12 feet, which would be more than enough to beat a goalkeeper.

This coefficient of drag is what is being altered by the new ball. The fewer panels, rounder shape and aero grooves all have an effect. The fewer panels and rounder ball allow the striker to get more of the ball in his shot and also control the rotation on the ball. This should result in higher ball speeds off the players boot and cut the initial drag. The increased rotation creates the effect of moving air on one side of the ball faster than on the other, creating a force which makes the ball swerve more. The aero grooves produce turbulent flow around the ball (similar to the grooves on a golf ball) allowing it to also cut down on drag and fly through the air faster and further.

The extra movement on the ball occurs as the ball slows down and the drag forces take effect. The higher the ball speed and spin initially the more these drag forces can pull on the ball as it slows down. The design of the new ball has allowed us to use physics to better determine what will happen to it. The multi-paneled soccer balls of the past were far more unpredictable because of the seams, stitching and shape which affected its flight and movement.

To simplify all that, the "Jabulani" ball gives the strikers more control than they have ever had before and the ball flies faster through the air, making movement of the ball more dramatic off a well hit shot. The striker still needs to have control and power and be capable of imparting them to the ball in a perfect sequence to have the desired "unpredictable" effect.

Goalkeepers will learn to adjust to the new flight and speed of the "Jabulani" ball and then we can wait in anticipation for World Cup Finals Brazil 2014 to hear the new complaints about the "unpredictable" new ball.

In the meantime we will enjoy watching some spectacular goals and watch out for video that we can analyze that might show how the strike made the ball move like that.

Go Bafana Bafana and USA soccer.
Laduma! (Goal !)

No comments:

More Recommendations