## Tuesday, November 13, 2012

### Coefficient of Restitution $C_R = \frac{v}{u}$

Dear Sphaeralogists,

This formula is the key to what makes the SuperBall so special and such darned-tooting good fun.  Essentially it measures the velocity of return of an object dropped, thus indicating the amount of energy maintained after it has struck a surface.  The higher the number, the bouncier the object.  Some studies have measure the Coefficient of Restitution of the Super Ball® at .92.  This is extremely high in physical terms and indicates that there is tremendous bounce in these here balls.  This measurement is only considered with the balls dropped without propulsion.  As we know, a little kick can really make these spheres soar.  Consider this wiki entry for more on this subject:

You can also use this formula to measure the COR, this time a measure of return height: $C_R = \sqrt{\frac{h}{H}}$

Here is one study of the measure of the COR of the Super Ball conducted at Colorado State:

They used this formula as their basis of measurement. In any case, the science of the bouncy ball is very cool and worth a look see, so you should all take a gander to brush up on the true nature of your favorite ball.

Sincerely,

The Founders