Speed and Spin analysis

[chux10sed]

Hi,
Great job you guys did with the speed and spin analysis of top players like Sampras, Agassi, Chang, etc.

Reminds me of a simple study I did in graduate school where I was attempting to analyze speed and accuracy. I was told to multiply the two variables if I wanted to look at them as a whole entity. Would that be worthwhile doing in your speed and spin analysis in the Heavy Ball page?

Very cool to learn that there's no such thing as a flatly hit tennis shot Great stuff!

[johnyandell]

Not sure how that works. We don't have the spin/speed data on the same shots at least at this point...anyone else have a thought here?

[GeoffWilliams]

In Ohm's law, the total power is equal to the total pressure multiplied by the total flow. The pressure in this case would be the velocity, and the flow would be the rpms. Say, a 93mph Nadal forehand, with 3000 rpm, would be: 279,000 or 279K fh Total power reading. In Kilometers/hr: A 452K fh. That would be a truer reading of how heavy a ball is, the velocity times the rpms, before hitting the ground or after hitting the ground as well, as the surface would affect the speed and rpm after reflection.

[julian1]

It does NOT work EXACTLY like that for baseline shots

In Ohm's law, the total power is equal to the total pressure multiplied by the total flow. The pressure in this case would be the velocity, and the flow would be the rpms. Say, a 93mph Nadal forehand, with 3000 rpm, would be: 279,000 or 279K fh Total power reading. In Kilometers/hr: A 452K fh. That would be a truer reading of how heavy a ball is, the velocity times the rpms, before hitting the ground or after hitting the ground as well, as the surface would affect the speed and rpm after reflection.

It does NOT work EXACTLY like that for baseline shots.
A product will NOT be a best metrics/criterion imho.
There are some known results describing forces in the case of SERVE.
tennis_chiro and phil were running a post on this subject for a while.
I will try to find a link.
I am on a tennis court right now.Sorry.

[tennis_chiro]

I think it is just a good way to get a relative measure

It does NOT work EXACTLY like that for baseline shots.
A product will NOT be a best matrics/criterion imho.
There are some known results describing forces in the case of SERVE.
tennis_chiro and phil were running a post on this subject for a while.
I will try to find a link.
I am on a tennis court right now.Sorry.

I don't remember a particular post on this although we did have some pretty esoteric ones. I don't think you get a "physics" approved actual measure of power but it seems to make a lot of sense in terms of trying to establish some relative comparison. To get true "power" you would have to start measuring the energy contained in the spin and adding that to the energy contained in the linear momentum of the ball. It would be interesting to investigate just in terms of the actual power it takes to generate the spins and speeds that Nadal is generating. You might end up starting to relate it to how much you can get the margins of error to increase vs. how much more time it takes for the ball to follow that arced path. It's definitely beyond me. I'm just trying to figure out how to get my address book from my Palm Treo to a form that I can get the info up into my new iPhone! And that has me just about overwhelmed. Makes me feel very old!

don

[chux10sed]

I believe that if you have two variables with different units to them, and you want to combine both variables into one number, I was told the way to do it is to multiply the two numbers.

In this case, spin X speed. One could create a name for the new product ... "spineeds" or some other such play on words. Not being a physics guy, I don't know, there may already be a word for this.

In order to be fair to the players being compared, one would probably have to try and keep the conditions they're playing under as similar as possible, or at least use the same number of attempts [measurements] at the task being examined. Easier said than done

[johnyandell]

Well eventually we will have some velocities to go with our spin data, so then you guys can try some of these calculations.

[julian1]

A good candiate

I don't remember a particular post on this although we did have some pretty esoteric ones. I don't think you get a "physics" approved actual measure of power but it seems to make a lot of sense in terms of trying to establish some relative comparison. To get true "power" you would have to start measuring the energy contained in the spin and adding that to the energy contained in the linear momentum of the ball. It would be interesting to investigate just in terms of the actual power it takes to generate the spins and speeds that Nadal is generating. You might end up starting to relate it to how much you can get the margins of error to increase vs. how much more time it takes for the ball to follow that arced path. It's definitely beyond me. I'm just trying to figure out how to get my address book from my Palm Treo to a form that I can get the info up into my new iPhone! And that has me just about overwhelmed. Makes me feel very old!

don

Don,
a good candidate to measure would be the following expression

const1*v*v + const2*(rpm)*(rpm)

where

const1 and const2 to be established from physics of forehand(say)
v is a speed of a ball
rmp denotes rotations per minute ( a symbol introduced in one of first posts above)

I think
const1=0.5*m
where m is a mass of a tennis ball
and
const2 is proportional to m*r*r
where
r is a radius of a tennis ball
For a second term please see

http://hyperphysics.phy-astr.gsu.edu/hbase/rke.html

Regards,
Julian

[GeoffWilliams]

From personal experience, the heavy ball is created by both velocity and spin. Some serves just don't feel heavy, even though their velocity is the same, as those with the heavy spin at 100mph+. The felt vel./spin rates also depend on the surface speed and roughness, hence, the slower surface reduce the amount of both felt on frame. Both Sampras and Beckers serves were described as heavy, although they served in the 120-126pmh range usually. Sampras also averaged 108mph on his second serve in the us open one year, but that's with a ton of spin.

[julian1]

Please see my post above

I believe that if you have two variables with different units to them, and you want to combine both variables into one number, I was told the way to do it is to multiply the two numbers.

In this case, spin X speed. One could create a name for the new product ... "spineeds" or some other such play on words. Not being a physics guy, I don't know, there may already be a word for this.

In order to be fair to the players being compared, one would probably have to try and keep the conditions they're playing under as similar as possible, or at least use the same number of attempts [measurements] at the task being examined. Easier said than done

Please see my post above

[tennis_chiro]

Exactly!

Don,
a good candidate to measure would be the following expression

const1*v*v + const2*(rpm)*(rpm)

where

const1 and const2 to be established from physics of forehand(say)
v is a speed of a ball
rmp denotes rotations per minute ( a symbol introduced in one of first posts above)

I think
const1=0.5*m
where m is a mass of a tennis ball
and
const2 is proportional to m*r*r
where
r is a radius of a tennis ball
For a second term please see

http://hyperphysics.phy-astr.gsu.edu/hbase/rke.html

Regards,
Julian

It's worth taking a look at the link, but it is just the sum of the rotational and linear kinetic energy that separates the "heavy" ball from the simply fast one at the same speed. I must have said it here before, but my definition of "pace" from Jerry Alleyne is deceptive speed. When someone hits the ball efficiently, it has a lot of energy, both rotational and linear, even though it doesn't look like that person is hitting very hard. A less efficient, perhaps more violent swing may produce a very fast ball, but it is less likely to surprise the opponent the same way.

But it's nice to realize we were not just imagining it when we said we thought someone's ball was "heavier" than someone else's even though they seemed to be at the same speed!

don

[julian1]

Topspin and side spin

Don,
two very TRIVIAL remarks:

two components produced by topspin and side spin ( for example Nadal)
can be separated in a formula ABOVE as well.

An issue of a topspin used against a under spin of an OPPONENT can be discussed
as well.
It gets a bit tricky in a case of a right hander playing a left hander.
A Tokyo match of Nadal vs Murray provides a lot of clips for a second point

http://espn.go.com/watchespn/player/_/source/espn3/id/256200/size/condensed/

Deception and suprise are NOT my forte.
regards,
Julian
julian mielniczuk uspta certified pro juliantennis@comcast.net Ph.D
www.julianmielniczuk.usptapro.com Courtside Tennis Club,Bedford,MA

[chux10sed]

Julian,
Very cool link on Rotational Kinetic Energy. Wish I was sophisticated enough to fully understand it all

I recall Arthur Ashe writing about his experiences with hitting with Rod Laver, saying the ball felt like a "brick."