World Cup soccer ball travels faster and farther at high altitude


World Cup players might notice strange things happening to their kicks due to the peculiar aerodynamics of playing high-altitude football at the stadium in Johannesburg, South Africa, a NASA scientist.

At altitude, the air pressure is lower, as are aerodynamic effects such as drag and lift, causing the balls to ultimately move faster and straighter than they would at altitude. lower. Johannesburg is 5,500 feet (1,680 meters) above sea level, even higher than Denver.

“When they play there, the ball will behave differently due to the density of the air compared to other stadiums,” said Rabi Mehta, an aerospace engineer at the NASA Ames Research Center in Moffett Field, Calif. “When you watch the games recently, you often see a long time past that overrun, and I think it’s because of that effect.”

Physics in the field

Drag is the force of air resistance that opposes the movement of a ball and slows it down, while lift is a force that deflects the ball from a straight path. Both forces are caused by the presence of air, so with less air molecules around, these forces are reduced. So the same Johannesburg kick compared to a sea level kick would make a soccer ball travel faster and on a less curved path.

Players who are aware of the effect of altitude on aerodynamics might have an advantage over those who are not, Mehta said.

“If they understand what’s going on in certain situations, it improves their performance,” Mehta told LiveScience. “When the person makes a pass, they have to realize, ‘I don’t have to hit him as hard as at sea level or it’ll go out of bounds.'”

Additionally, the altitude can be physiologically harsh for players who are not used to it. Less atmosphere means less oxygen to breathe, which puts pressure on athletes as they have to breathe harder to get enough oxygen for their tense muscles. People can adapt to the altitude and their bodies will begin to produce more red blood cells to take advantage of the available oxygen. But it does take time, so players who live at high altitudes or arrive early enough to acclimatize have a definite advantage.

Punch

Mehta also researched the aerodynamics of the new soccer ball used in the 2010 World Cup. For competition, Adidas introduced a new ball called Jabulani (Zulu for “celebration”). The new model is made up of eight panels, compared to 14 previously, and features special aerodynamic ridges on its surface.

The ball is an adjustment to a previous new ball called Teamgeist, introduced for the last World Cup in 2006. At the time, Adidas said it was the most accurate soccer ball in the world, although players have complained that it does not work as they used to. .

Mehta said Jabulani would likely have the same quirks as Teamgeist.

A main problem is what is called “knuckle-balling”. An articulation ball is a ball that deflects or turns in unexpected directions. This happens because the ball is kicked straight, without spinning.

Ironically, this lack of effect on the ball causes its trajectory to curve due to aerodynamics. The ball isn’t perfectly smooth because of the seams between its panels, and now because of the added ridges. These irregularities cause an asymmetric airflow around the ball, creating lateral forces that push the ball into a yaw.

The new edges and the overall design make Jabulani even easier to hit at the speeds commonly used when taking free kicks around the end zone.

The punch isn’t necessarily bad – sometimes it helps scare the goalkeeper away if a ball flies at the last minute. But players like to be able to anticipate where their kick will land, and the new ball will need some tweaking, Mehta said.

Mehta shared some of these findings with a group of students who were invited to test the new bullet at an event hosted by NASA’s Ames Fluid Mechanics Lab.

“It’s amazing how excited kids get when you start talking about sports,” Mehta said. “All of these efforts are aimed at making children more interested in science and engineering.”