Soccer: Bending the Ball

"Bend it like Beckham" is both an offbeat title to a feature motion picture, as well as a universal catch-phrase recognizing the superlative skills possessed by David Beckham, the English national captain, and soccer icon. Using both his innate feel for the ball and through the application the principles of physics as they relate to objects traveling through the air, David Beckham has demonstrated throughout his career an unsurpassed ability to kick a soccer ball around a wall of free kick defenders, charting an elliptical route to the goal.

David Beckham is not the only noteworthy practitioner of the bending art in soccer—Roberto Carlos of Brazil and the legendary Pelé were equally adept at driving the ball from seemingly impossible angles on free kicks for a score. Bending the ball is a technique practiced by all soccer players who seek to develop comprehensive ball skills.

The "bend" is soccer jargon for the curve of the ball as it travels through the air on a free kick. Like the curve ball thrown by a baseball pitcher, or a volleyball when served, the spinning soccer ball when kicked tends to deflect the air moving past it, and the air responds by deflecting the ball on its path.

This physical principle is referred to as the Magnus force. When the ball is spinning after being kicked, the air through which the ball travels tends to follow a longer path around one side of the ball than the other, as the air is dragged along by the turning surface of the ball. The air following this longer path will bend more sharply, which results in a significant drop in air pressure on that side of the ball. The ball will then be pushed toward its low-pressure side, causing deflection.

A further physical consideration in understanding the bend of the soccer ball in flight is the wake deflection force. As a moving ball will leave a turbulent wake of air behind it, the spin of the ball will deflect the wake to one side. This deflection will shift the air stream flowing around the ball; the air stream will in turn push back on the ball. The Magnus and wake deflection forces operate in the same direction, contributing to the remarkable curvature on free kicks from players such as Beckham.

In a relatively low scoring game like soccer, the ability to take advantage of every offensive opportunity is critical to success. The "bending" power of a skilled player has the effect of extending a teams effective scoring range.

see also Baseball curve ball.