# Horizontal coefficient of restitution

1. Oct 11, 2009

### Psych Berry

1. The problem statement, all variables and given/known data
I'm supposed to determine the [vertical] coefficient of restitution of a tennis ball, and the horrizontal coefficient of restitution, and if possible produce an equation or ratio connecting the two.

Vertical CoR: 0.760
Constant x-component velocity: 0.853 m/s

2. Relevant equations
sqrt (h2/h1) = |v2/v1|

3. The attempt at a solution
I've already calculated the [vertical] coefficient of restitution, and googled to find out that my answer is consistent with that of standard tennis ball.
At this point I just don't know how to calculate the horrizontal CoR. My textbook and lab manual don't mention it, and I can't figure out what relationship they would have.
Can anyone help me out here?
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Oct 11, 2009

### rock.freak667

From what I am told, the coefficient of restitution for when objects collide in two planes, is found by taking the ratio of the vertical component of the velocities. So I don't think there is such thing as a horizontal coefficient of restitution.

3. Oct 11, 2009

### Psych Berry

Maybe that's true, my lab manual where the questions are stated is definitely not written by people with doctorates in physics. But that's merely terminology. It wouldn't change my question.

If there is no such thing as "horizontal coefficient of restitution" then what would the corresponding horizontal ratio be?

Thinking about it more I assume it would be based off the regular coefficient of restitution, since horizontal velocity is constant, therefore the distance traveled per bounce is a function of time, and the time of each bounce is dependent on the max height reached, which is in turn dependent on the CoR. But I don't know how to state that in an equation, or if I'm even on the right track.

4. Oct 11, 2009

### tiny-tim

hi rock.freak667!

yeah, I've never heard of it before either …

but I just googled it, and apparently it does exist (I couldn't be bothered to read about it though )

5. Oct 11, 2009

### Psych Berry

Well then, if it exists can anyone enlighten me as to how to obtain it?

6. Oct 11, 2009

### rock.freak667

Well according to http://www2.physics.umd.edu/~mfuhrer/course/spr02/AJP/AJP00482.pdf" [Broken], it seems that you obtain the horizontal coefficient of restitution the same way you get the vertical one. You just use the horizontal components instead of the vertical ones it seems.

Last edited by a moderator: May 4, 2017
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