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Historians believe the first American footballs were supposed to be round, but they became oblong by inflating pig bladders covered in leather. This helped coin the term “pig skin.” The prolated spheroid shape became a tradition as the early game of the 1800s evolved from a kicking sport to a passing one in the 1900s, according to the Smithsonian.

The speed and accuracy of the modern game has evolved, but the same physics of the earliest footballs still applies today, according to Southwest Research Institute’s Mechanical Engineering Division. It starts when a quarterback’s fingers flick the laces as he passes a football forward. This creates the spin, or spiral, that sets in motion football physics.

How pigskin gyroscopes reduce friction in football physics

SPINNING GYROSCOPE - A spiraling football turns it into a spinning gyroscope. The gyroscopic 'stiffening' keeps the ball going in crosswinds in the quarterback’s intended direction. The spiral helps the ball maintain accuracy (just like gyroscope autopilots keep airplanes on course).

REDUCES FRICTION - Spiraling reduces friction between the football and air so the ball travels farther before losing speed. It causes friction as it drags some air with it, but the spiraling mixes that air with still air it passes through. Fluid dynamicists call this ‘tripping the boundary layer.’


Visit the Southwest Research Institute’s Mechanical Engineering Division to learn more about the physics of fluid dynamics.

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Southwest Research Institute® (SwRI®), headquartered in San Antonio, Texas, is a multidisciplinary, independent, nonprofit, applied engineering and physical sciences research and development organization with 9 technical divisions.
12/09/15