# How to bend it like Beckham

Now that David Beckham won’t be appearing at the London 2012 Olympics, other members of Team GB wanting to brush up on their free-kicks can rest easy. University of Leicester physics students have published a paper which sets out the optimum way of kicking a football (soccer ball) in order to make it bend into the goal.

The ex-England captain’s curling free-kicks became legendary, and even inspired the title of the 2002 film Bend It Like Beckham. Now, four master’s students at the University of Leicester’s Department of Physics and Astronomy believe they have discovered a formula to explain how the football curves when a player puts spin on it. Jasmine Sandhu, Amy Edgington, Matthew Grant and Naomi Rowe-Gurney found a relationship between the amount a football bends in the air, the speed it is travelling and the angular velocity — or “spin” — applied to the ball. When a football spins in the air, it is subjected to a force called the Magnus force — which causes it to curl sideways from the direction it was originally kicked.

The group found that the distance a ball bends (D) as a result of this force is related to the ball’s radius (R), the density of air (ρ), the ball’s angular velocity (ω), it’s velocity through the air (v), it’s mass (m) and the distance travelled by the ball in the direction it was kicked (x). For instance, if a player standing 15 metres away from the byline kicked an average football so that it was travelling at a velocity of 35 metres per second and had an angular velocity of 10 revolutions per second, the ball would bend around 5 metres towards the goal.

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