Secret Of David Beckham's Free Kick

When David Beckham takes free kick, he kicks the right hand side of the ball. The ball spins anti-clockwise and curls to the left as it travels. Given that the air will be travelling over the right hand side of the ball faster than the left, why doesn’t the ball curve to the right due to the lower pressure produced?

Because the ball is spinning on itself, the air on one side of the ball is moving past it faster than the other side. Let us assume that we are looking at the ball from above it as it flies through the air. The ball spins anticlockwise, so relative to the ball, its right hand side (RHS) is moving towards the front of the ball, while its left hand side (LHS) is moving towards the back of the ball. This actually means that the air flow on the RHS is slowed down at the surface of the ball, due to friction.

On the other hand, the air flow on the LHS is speeded up. This is the source of the force. The every same principle that allows planes to fly (Bernoulli’s Principle). When air moves slightly faster, the space between molecules is very slightly increased; this means a decrease in the pressure at that point. A decrease in pressure is equivalent to a sucking force.

Similarly, when the air is slowed down on the RHS, an increase in pressure results in a pushing force. Overall, the ball will start to swerve towards the LHS. If you kick the ball with the inside of the left foot, the ball spins clockwise, and the ball this time swerves to the RHS. If you increase the spin of the ball, the force will increase.