How do you throw a perfect spiral? Football physics, explained

Transcript

How do you throw a perfect spiral? Spin it. A football spinning fast around its long axis behaves like a gyroscope: it resists being tipped. And every throw gets tipped. Your hand never lets go perfectly, so the ball leaves with a small wobble. With little spin, that wobble takes over, and the ball wobbles wildly, even tumbles: a wounded duck, with lots of drag. Now crank up the spin. At around ten turns a second, six hundred r p m, the same shaky release settles into a small, tight circle, the nose tracing a little cone. Now watch the whole arc. A ball that just held its angle would still point up as it came down, and arrive nose high. But the air presses on the tilted nose, and a spinning ball answers sideways, so the nose slowly swings around to follow the path. That's why a good spiral comes down nose first, into the receiver's hands. The spin itself comes from the ball rolling off your fingertips as you let go. Try it yourself at Explainer Tools dot com.