Physics in the real world

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in the real world

QuestionWhy does a football curve when kicked?

An illustration of case when a kicked football curvesRoberto Carlos scored an amazing goal while curving the soccer ball during the game ofBrazil vs. France on 1997

Why does this happen?

ExplanationThe physics of soccer or football mainly can be explained by mechanics.What makes the soccer ball curve under those circumstances is a result of aerodynamics. Kicking the ball off-center gives it a good spin and the ball will most likely curve.

When a ball is flying through the air without spinning the flow distribution around the ball is symmetric. However, if the ball is spinning, the flow distribution around the ball is asymmetric, since there is a preferred direction for the air to go around the ball. This effect can be seen in the following picture:Explanation

When the flow around the ball is symmetric (the ball is not spinning) the pressure in both sides of the ball is equal. When the flow around the ball is asymmetric, due to the spinning motion of the ball, the velocity on one side of the ball is faster than on the other side, which makes a lower pressure zone on one side and a higher pressure zone on the other side. This pressure difference generates a net force which forces the ball to curve. Explanation

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