Author: Edgar Zhu
Editors: Katelyn Ma and Liane Xu
Artist: Tiffany Chen
The ball flew in a beautiful arc around a wall of defensive Osasuna players and into their net. It was Messi's fifth straight free-kick of the season. His incredible skill was Barcelona’s nuclear weapon, destroying opponents one after another. This article will give insight into the basic physics theories and principles that play a role in making it possible for Messi to shoot curveballs.
The fundamental principles of the phenomenon of the curveball are “Bernoulli's principle” and the “Magnus Effect”. Bernoulli’s principle demonstrates that in a fluid system, such as airflow or water flow, the faster the flow, the less pressure the fluid exerts. Bernoulli’s principle explains how airplanes can create lift under their wings- air pressure is different on each side of the wing due to its curved shape. The Magnus Effect demonstrates how an object will move in the direction of lower pressure.
In the case of Messi’s beautiful goal, these principles are well-established. When Messi’s left foot hits the left side of the ball, the ball is given a linear momentum. The linear momentum helps the ball move from its initial location to the final position. However, with only a straight motion, the ball will be intercepted by the wall of defensive players. To bypass the wall, Messi also gives the ball a clockwise rotation. As the ball spins through the air, it spins the thin layer of air on its surface. The linear velocity of the thin layer of air on one side of the ball is superimposed with the forward velocity of the ball, causing great resistance to the head-on airflow. The opposite is true on the other side of the ball, where the speed of rotation and the speed of advance weaken each other, causing the airflow on both sides of the ball to move at different speeds than the ball itself.
According to Bernoulli's principle, the high-velocity side of the flow forms a zone of low pressure, while the other side forms a zone of high pressure. The net result of the pressure difference between the two sides of the ball is that the net force from the high to the low-pressure area is acting on the ball, or the Magnus Effect, causing it to deviate from its original straight line of motion.
“GOAAAAAAAAL!”
Several seconds later, you will see a defeated goalkeeper and celebrating Barcelona players.
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