practice

1. Write something.
2. Write something else.
3. Write something different.
4. Write something completely different.

conceptual

1. This is a real problem that I am sure has something to do with precession. There's really only one interesting question in the physics of football (American football — not soccer) When a quarterback throws a "tight" spiral, he has to do it by putting a large rate of spin on the ball and he has to do it by launching it with no angle of attack; that is, the long axis of the ball has to be parallel to the velocity of the ball. When he does that, the ball will execute a motion in which its long axis maintains its tangency to the direction of motion. How can that be? What's causing its rotation? (I would ask, what's causing its precession?)