Aerodynamics: Force and Ball

When you hear the word aerodynamics, the first thing that comes to mind is airplanes and pilots. There are other applications that apply. For instance, the passing of a football. A football that is thrown into the air has inertia. This is the tendency of an object in motion to remain in motion. But because of gravity the ball is pulled down and resistance that slows the ball down. A quarterback through the motions of his and body, must balance the forward momentum that he gives the ball, fighting gravity and air resistance that pulls and slows it down. Aerodynamics is involved during passing because of the spin that is applied. The better the spin the straighter and further the ball will travel. This is accomplished by the quarterback throwing the football over handed or a sidearm motion to giving it the spin required. The spin causes the ball’s angular momentum points in the direction of its long axis. At same time due to air drag, torque is pointing perpendicular to the angular momentum. The ball travels on a semi-parabolic curve and wind torque produces a small change in the ball’s angular momentum. This allows the ball to continue to turn around its trajectory. Therefore spinning stabilizes the football through angular momentum and torque. Throwing in this manner orientates the ball giving it the smallest possible cross sectional area against the oncoming air; this causes the least amount of aerodynamic drag. This is important for quarterbacks as while as managers to know, because if the ball does not spin properly, the wind will cause if tumble and lose its forward momentum (duck). Managers (coaches) want to make sure that there quarterback understands this basic principle. Not throwing a proper pass can be the difference between winning or losing.

Reference:
http://www.faqs.org/sports-science/Fo-Ha/Football-Passing-Aerodynamics.html