The new ball is not the only thing that will cause controversy in the World Cup according to a leading sports engineer, who believes the low air density in South Africa’s high-altitude stadia will result in a tournament of high-speed shots.
Professor Steve Haake, head of sports engineering at Sheffield Hallam University, has been investigating how South Africa’s high-altitude venues, such as Johannesburg’s Soccer City, will affect games throughout the competition.
Professor Haake said: “High altitude means lower air density and subsequently less drag on the ball. Combine this with the faster Jabulani ball and we could be seeing significantly faster shots and free kicks. Johannesburg, for example, will have around 20 per cent less air density than Cape Town. If teams don’t factor this into their training they could fall foul of the faster shots it’ll produce.”
According to Professor Haake’s research, a non-spinning 18 metre free kick hit at about 60mph, with no wind, would take around 0.82 seconds at sea-level in Durban or Port Elizabeth. The same shot would take about two hundredths of a second less time in Johannesburg. This means the ball in Johannesburg would be around 41cm ahead of the ball in Durban in real time.
Professor Haake said: “Higher temperatures will decrease air density even further, so goalkeepers will need to be prepared for fast, unpredictable shots. Finger-tip saves can make all the difference and a ball that is over two diameters ahead of where they expect it to be will really test their skills.”