Spiral: Newsletter Challenge (08/22/06)

Throwing the ball with a spin on it stabilizes the ball (gyroscopic effect) and allows more energy to be applied to the throw and increases the distance it can be thrown.

It also makes it a whole lot easier to catch!

Whiy throwing a spiral so important?

Because throwing a fit can get you tossed out of the game.

You mean like Jim McMahon of the 80's Chicago Bears? Pretty good answer - can't wait for your next one! Football Fan in Florida (NOT the Dolphins!)

The angular momentum keeps it moving straight, minimizing drag from the air (with it's point facing the front rather than the fat side), and being much more predictable and easier to catch.

NASA also does this when launching satellites from the Shuttle bay. Although there is no air to cause drag, the gyroscopic stabilization keeps it from tumbling.

I've seen a few of these videos and it is interesting to watch them slowly lift out of the bay with a slow spin. If memory serves, I think they start the object rotating, then eject the satellite.

The spin results from an angular momentum applied perpendicular to the longitudinal axis of the football. The throwing arm imparts a force parallel to the longitudinal axis and the drag of the atmosphere imparts a force in the opposite direction. Gravity imparts a downward force on the ball. The angular momentum of the spin keeps the ball's forward momentum parallel to the longitudinal axis therefore minimizing the effect of atmospheric drag. This is a result of the gyroscopic effect. If you lay a football on a flat, level surface with it's longitudinal axis parallel to the ground and spin it, it will slowly rise until its spin is perpendicular to the ground and the longitudinal axis. In other words it will stand up on its end.

A couple of points to consider: 1) The added rotation (in conjunction with the rough pigskin surface) increases the boundary layer turbulence, effectively reducing the drag. 2) If the QB could impart the throwing force with no eccentricity from the CG (and assuming the CG lines up with the centre of drag) then the spiral would not be needed. As it turns out, QBs do tend to have eccentricities (that's another story) so that the ball is given a tumbling moment from the start, in addition to the imbalance from the laces. These conspire to instability which the rotation about its longitudinal axis (spiral) helps to even out. The bigger the imbalance, the faster the required spin to counter it.

Check the physics off a bullet getting an axial spin by the spiral of the barrel

Yes, but just don't check the physics while standing in the path of that bullet!

Opps, maybe I should not have said that. I just might have eliminated a candadate for the Darwin Awards somewhere. :-)

it got thrown away when submitted. Sorry you missed it.

Answer - do you remember Joe Kapp of the Vikings? Does the term "wounded duck" mean anything?

Ouch! That stirred up some unpleasent memories.

My Dad played college ball in the early 30s in Helena MT. The ball was a little less pointed. But, for what little they passed he said the spiral was to prevent the defenders from getting the ball. Ever try to catch a greased pig?

Works both ways! The defensive team has just as much chance as the offense to catch a spinning ball!

You are absolutely right.

Talking about spirals. What about a downward spiral. How 'bout them niner's

Too funny!

Boat tail design as like a bullet. Laces on a slight forward angle to help keep the rotation, such as a bullet leaving the barrel of a gun. It actually helps in the dilivery of the throw, giving the ball more direct path in flight. The harder the ball is thrown, the greater the force in keeping the rotation, the faster the ball travels to the intended receiver. Then there is the arch of trogectory for distance, the laws of gravity do tend to take over when the ball is thrown with a weak arm.

Ok, I'm guessing But, Because of its shape a foward spiral motion is the only way the football can be thrown with any distance and accuracy. Simple enough.

The spiral along with the forward motion of the ball acts like a drill bit and drives into your arms.