Madrid, 5 (European press)
Only a few researchers have studied why a soccer ball flies such a unique trajectory, navigating through the air with remarkable accuracy, but also deflecting, wobbling, and even spinning as it lunges across the field.
“When a quarterback makes a good ball pass, the trajectory of the ball is remarkably similar to that of an artillery shell or bullet, and the Army has spent tremendous resources studying how these projectiles fly,” John Dzielsky explained in a statement. Stevens Institute of Technology researcher, professor and mechanical engineer whose work has been published in the Open Journal of Engineering of the American Society of Mechanical Engineers.
“Using well-understood ballistic equations, we have been able to model a football flight more accurately than ever before.”
In fact, Dzielsky said, while the ballistic equations themselves aren’t terribly complex, the motions they predict could be. The equations contain many terms that represent all the ways air can affect projectile motion. The first challenge was to consider each variable in turn to identify which variables are important when used in a new or different context.
Dzielsky and co-author Mark Blackburn, Stephens’ senior research scientist, first took a holistic approach, modeling everything from a quarterback’s ingenuity to the effect of crosswinds and the effect of Earth’s rotation, then deriving equations that largely eliminated factors that don’t. Affect the course of the football journey.
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For example, during a 60-yard lane, the Earth’s rotation changes the lane’s end point by only four inches. “It turns out that the rotation of the earth doesn’t have much of an effect on the football pass, but at least now we know that for sure,” Dzielski said.
Modeling a soccer flight highlights what separates good passes from bad ones. Not only did Dzielsky and his colleagues show that a helical pass can swing at a slow or fast rate (or a combination of both), but they were also the first to calculate what those frequencies are in football. If the football vibrates slowly, it is well thrown. If he wiggles quickly, the quarterback either twists his wrist (like turning a screwdriver) or pushes it to the side when the ball is thrown. The wrist could have been sprained due to the player’s injury.
“The midfielders and coaches already know this intuitively, but we were able to describe the physics at work,” Dzielski said.
The other, more surprising finding was that the Magnus effect, which causes a baseball to slip or yaw due to changes in air pressure, has remarkably little effect on the spinning soccer ball. Dzielsky explained that the soccer ball rotates along the wrong axis to trigger the Magnus effect, so any deflection in the flight path must come from a different source, such as the lift produced when the ball spins through the air.
“A lot of people think that soccer balls are deflected to the left or right due to the Magnus effect, but this is not the case at all. The effect of the Magnus force is twice that of the Earth’s rotation.” , He said.
Moreover, Dzielski and Blackburn showed, for the first time, that this deflection is closely related to the reason why the ball goes down at the end of a pass when thrown with its nose.
Although Dzielski’s and Blackburn’s work represents the most accurate model of football’s itinerary to date, Dzielski cautions that more work remains to be done. Because a soccer ball twists and turns as it moves, it is almost impossible to use wind tunnel studies to accurately record the aerodynamics of the ball in motion. “This means that we don’t have good data to feed our model yet, so it’s impossible to create an accurate simulation,” he said.
In the coming months, Dzielsky hopes to find funding for tools that can capture aerodynamic data from a free-flying soccer ball in real-world settings, not just wind tunnels. “This is the only way we will be able to get the kind of data we need,” he said. “Until then, a really accurate and accurate method of modeling the trajectory of the ball will remain elusive.”