Have a Question for Me?

[ajaxphagura]

Looking for some coaching for my 12 yrs old

Hi John, I love your site it is truly very infomative . I was wondering if you give lessons to Juniors around SF Bay Area, recommend one..

Thx!!

-AJ

[johnyandell]

I don't. I only do video analysis consultations. There are a lot of goof junior coaches--what part of the Bay?

[ajaxphagura]

I read in number of your articles (bottom) saying you run a tennis school in sf, thats why I asked. Is it now run by your friend Kerry M?? If so can I have his coaching info, I can contact him.

Thx!!

-AJ

[johnyandell]

Kerry has retired and moved to Mexico! Steve Jackson has a new program at the Cal Club--they may take non-members, SFTC has some good coaches. If you are elsewhere in the bay area I can make suggestions.

[ajaxphagura]

We live in Castro Valley..so anybody around East Bay?? Thx!!

[johnyandell]

Michael Friedman at the Millennium Sports Club--he writes for us.
Or my friend Marc Moran at Club Sport Pleasanton--a big supporter of Tennisplayer.

[ajaxphagura]

Thx!! John for your help.

[emeralda]

John,

Linear momentum in the forehand is considered significant by some and also crops up in threads as you probably know. Do you have any views on this and are there any articles which support the 'linear plus angular' concept? Once the forehand is in motion I only see angular momentum and torque.

Don

[johnyandell]

You know those are mathematical concepts and to talk with any certainty about them goes beyond the scope of my work.

I glanced briefly at some of that debate on TW but I don't really see the point. If the pattern of the stroke is correct under the circumstances the momentum whatever it may be can take care of itself. I think it's a mistake to throw quantitative terms around without data.

[uspta146749877]

Please let me know

John,

Linear momentum in the forehand is considered significant by some and also crops up in threads as you probably know. Do you have any views on this and are there any articles which support the 'linear plus angular' concept? Once the forehand is in motion I only see angular momentum and torque.

Don

Please let me know whether it is OK to ask a question here.
Technically a post was addressed to John Yandell

[johnyandell]

Go ahead.

[uspta146749877]

linear momentum

John,

Linear momentum in the forehand is considered significant by some and also crops up in threads as you probably know. Do you have any views on this and are there any articles which support the 'linear plus angular' concept? Once the forehand is in motion I only see angular momentum and torque.

Don

Hi,
could you define "once the forehand is in motion "?
Is it:
1.at the beginning of a backswing
or
2. after a contact point

I assume the answer is #1

[emeralda]

Ground force starts the fh in motion and this appears to be 'converted' into an unwinding action. This appears to happen independent of the direction that the player is moving. It is not easy to find articles showing and if and when linear momentum fits in here and yet I often see the ambiguous terms 'put weight or transfer weight into the ball'

I do not intend to open a 'can of worms' on any issue here. I just wonder why it is not easy to find literature clarifying issues like this and I can't see how we can ever make enough measurements to developed clear conclusions using data from biomechanists. Tennis wisdom seems to be a patchwork good practical ideas and the curious mathematical side of me is looking for more unifiying theories and conclusions.

[uspta146749877]

Linear momentum

Ground force starts the fh in motion and this appears to be 'converted' into an unwinding action. This appears to happen independent of the direction that the player is moving. It is not easy to find articles showing and if and when linear momentum fits in here and yet I often see the ambiguous terms 'put weight or transfer weight into the ball'

I do not intend to open a 'can of worms' on any issue here. I just wonder why it is not easy to find literature clarifying issues like this and I can't see how we can ever make enough measurements to developed clear conclusions using data from biomechanists. Tennis wisdom seems to be a patchwork good practical ideas and the curious mathematical side of me is looking for more unifiying theories and conclusions.

Hi,
1.a linear momentum can be defined
a product of a mass of a player's body
multiplied by a speed of a player-
see reference of item #7 below

2.For a modern OPEN STANCE forehand a linear momentum is very often small- Please note the phrase open stance above.
There are some exceptions here: a forehand return of serve AND a forehand on a run

3.For a classic forehand coached ,say,25 years ago,a linear momentum
is much larger comparing to an open stance modern forehand.
Therefore a size of linear momentum differentiates between
a classic forehand and modern forehand.

4.A size of linear momentum depends on a size of a step foward ( step-in)

5.An USPTA certification manual could be of some help
if available to you

6.There is some info in an USTA High Performance Manual
but this manual is NOT widely available.

7."ITF Biomechanics of Advanced Tennis" could be of help
how data are collected and how terms are defined.

8.Please see as well Pages 83 and 84 of "Biomechanical Principles
of Tennis Technique" by Duane Knudson.

9.The related subject of Linear and Angular Kinematics
is discussed in Chapter 5 of "Fundamentals of Biomechanics"
by Duane Knudson.

10.Transfer of weight is related to a speed of center of mass

11.A bit different definition of a linear momentum
a linear momentum can be defined as follows:
say that you have a ball coming perpendicularly
to a baseline.
It is possible to measure a component of a momentum ( of a center
of gravity),specifically a component parallel to ground/surface of a court.
This component is would be called a linear momentum.
This defintion is NOT widely accepted



Please let me which one of points above was NOT clearly outlined.
Please let me know whether you disagree with some statements
regards,
julian usptapro 27873

[emeralda]

Thanks. First I need to check those references from the ITF book. Regards, Don