Spining ball
A bird's-eye view of a football spinning about an axis perpendicular to the flow of air across it. The air travels faster relative to the centre of the ball where the periphery of the ball is moving in the same direction as the airflow (left). This reduces the pressure, according to Bernoulli's principle. The pressure increases on the other side of the ball, where the air travels slower relative to the centre of the ball (right). There is therefore an imbalance in the forces, and the ball deflects in the same sense as the spin - from bottom right to top left. This lift force is also known as the "Magnus force", after the 19th-century German physicist Gustav Magnus.