# Thread: tennis ball example/coefficient of restitution

1. Originally Posted by topsquark
Yes. According to CaptainBlack (and I no longer have any reason to doubt his definiton) the coefficient of restitution is a ratio between the final and initial "vertical" components of the velocity. (Vertical referring to a normal to the surface of impact.)

-Dan
Thanks.
It was never taught in school.

Malay

2. []quote=topsquark]
Originally Posted by malaygoel
I haven't performed the experiment, but let me know the answer.

Malay
The point is, using my definition, the ball would eventually stop even over a frictionless surface. (e is always less than 1 in reality) If the ball had a horizontal component of velocity Netwon's 1st says it should always be in motion. A contradiction, so my definition can't be correct.

-Dan
[/quote]

It was not just a thought experiment, I did actually go out and perform
it. I have also been contemplating videoing it and analysing the frames of
the video to try measuring the coefficient .

RonL

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