Bend It Like Beckham
No, this column is not about that hilarious movie. Have you ever watched football on TV1? Some of you haven't, all right. Anyway, you do know David Beckham, euh? Ooh, doesn't really matter!
David Beckham is one of the most gifted free kick takers on Earth. His ability to swerve the ball past players is remarkable.
Anyway, do you know why the ball swerves? Why does a ball sometimes change direction when hit? There's a world of physics behind. But Not Scientific Science will reveal it (I hope).
When Beckham takes one of his free kicks, he always hits the ball on the latter's side. This makes the ball rotate upon itself. Now, a ball which rotates upon itself brings the air surrounding it to move around it but not in a symmetric way. Let me clarify this:
At the point A of the ball (the rotation of the ball is opposite to its final trajectory), the speed of the air around is high, higher than the speed of the air around the point B of the ball. Following me? Good. Keep reading then.
The greater the speed of a fluid, the lower is the pressure it exerts on a body (in this case the ball). This means that the ball thus goes to the lower pressure space.
Simple enough when you understand it, euh? Anyway here's a link I that's well worth clicking: Physics of sports.