|
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 center 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 center 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.
First published in Physics World magazine, June 1998
pp25--27. http://physicsweb.org/article/world/11/6/8
|
Spinning ball
