Superball Physics!

I’m trying to catch up on my reading by skimming through back issues of American Journal of Physics when I found this one in the March issue: “Impact behavior of a superball,” Am. J. Phys. 83, 238-248 (2014). It’s a fun little article that covers some of the basics that you can find elsewhere like how the properties of a superball (specifically its high coefficient of restitution aka COR and its high tangential COR) make for fascinating behavior like  how you can make a superball bounce back and forth by giving it backspin. On each bounce, it will reverse spin and keep going for quite a while.

The paper is fun, but they also do a lot of careful measurements on how different types of balls slide when they hit a surface. To do that, they used a very low-tech approach. Bounce the balls on a blackboard surface with wide chalk lines. When the ball strikes, if it slides, it smears the chalk lines. How the lines get smeared depends on the type of ball, the coeffience of static friction, the coefficient of restitution. 

Of course, at some level, the best thing is simply that how many fields can you play with superballs and get a published paper out of it?