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Grandpa -

Hi, I'm doing a report on the physics of football, and I was wondering if you had any info or could tell me where I could get some.  I need all types of information, about throwing the football and other things in football that are related to physics.  Can you help me out?

Brad eier    05 Feb 2000


Dear Brad -

There's lots of physics in football.

If it weren't for gravity, when the quarterback threw the football up, it would never come down. 

The pressure in the football must be about nine pounds per square inch more than the atmospheric pressure - to give the ball shape and the right firmness.  When you pump it up, your meter will say nine pounds - but it's really about 24 pounds per square inch.  The atmosphere is about 15, and the football is nine more than that.  You'll have 24 inside the ball and 15 outside the ball, so that the inside has 9 more than the outside.

There has to be a coefficient of friction for anyone to run.  On wet grass, it's not as much as the players would like, but there still is some friction.  Otherwise, the players would just slip and couldn't move forward at all.

When the football is thrown and a spin is put on it, centrifugal force keeps the ball aligned during its flight.  Other sports have a spherical ball, and this is not as noticeable for those.  Also, the ball will follow a shaped path called a parabola.

When a player fakes to the left and then goes to the right, he's taking advantage of the inertia of the other player.  By being ready to change the direction of his own inertia, while the other player continues on his way, this player moves another way and avoids the contact.

In the huddle, sound waves move through the air and allow all the players to hear the player who makes the calls for plays.

If it weren't for light, nobody could see to play, and nobody could watch the game.

A player must accelerate to get up to his running speed.

I'll bet you can go on and on now with other ideas about physics in football - and in other sports as well.

- Grandpa

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