For the learned.

[10splayer]

Coming from a severely limited science background, i have a question for you in the know. I'm constantly reading about "adding mass" to the swing. I have always been under the impression that the mass in the equation was the racquet, and thus a constant. That the only real variables were path and racquet head speed. Am I wrong?

[julian1]

Other variables

Coming from a severely limited science background, i have a question for you in the know. I'm constantly reading about "adding mass" to the swing. I have always been under the impression that the mass in the equation was the racquet, and thus a constant. That the only real variables were path and racquet head speed. Am I wrong?

Other variables are:
1.strings ( tension,hybrid/no hybrid,gauge,texture,how powerful chosen strings are,etc)
2.a location of a ball on strings ( for example location vs a sweet spot)

Please ask some questions and I can expand above

[bottle]

What about body weight going into the ball? Racket alone isn't much mass.
Tilden: "'Speed' is the actual rate with which a ball travels through the air. 'Pace' is the momentum with which it comes off the ground. Pace is weight. It is the 'sting' the ball carries when it comes off the ground, giving the inexperienced or unsuspecting player a shock of force which the stroke in no way showed."

[GeoffWilliams]

Stick speed is not translated fully without a locked wrist at contact, so the frame cannot go "back" any further against ie, a loose wrist, which will absorb much of the mass and speed of the frame at contact if it is looser than a locked back wrist.

"The better the player, especially men in good physical condition and good tennis technics, will choose heavier, less rigid racquets with a mid/mid-plus frame and often thicker gauge strings, a denser string-bed at lower tensions. Instead of just playing with the arm, he will put much more weight on the ball by advancing all of his body during the strokes, often accelerating the head of the racquet with a "whipping effect from the wrist, and a generous follow through. The control of the length of the ball will be ensured by the spin generated by the contact of the stringbed to the ball, either by the angle of strike of the stringbed on the ball or the rotation of the racquet during the contact with the ball, and often a combination of both of these actions.'

A speed ball versus a heavy ball. What's the difference? Heavy spin.

The result is a ball that is noticably slower as it leaves the racquet, the flight of the ball is more rounded but this initial speed will be maintained longer and even increase after the bounce of the ball. The physical effort to return this ball is far more important than in the 1st example, we say that this is a "heavy ball" it has a lot of weight in it, this is the power that has been transmitted to the ball by the player.

[stotty]

I agree with bottle. Body weight, as in weight transfer, has to be a factor. Tsonga, weighing 91 kilos, hits the ball harder than Gilles Simon, weighing 70 kilos. Both players are equally technically sound...gotta be something in that?...volume of weight transfer has to be factor?

[DougEng]

Mass, Body Weight, etc

Conservation of momentum and kinetic energy is critical. A perfectly elastic collision conserves kinetic energy such as a new tennis ball colliding with a stone wall. Now assume the wall can move, then the ball might gain kinetic energy. Loose strings, a loose grip or collision on the racquet away from the center of percussion will diminish kinetic energy of the ball. Its a paradox since a loose grip can allow the body to relax and generate racquet head speed. However, an off-centered hit with energy loss due to racquet twisting (as a result of a loose grip) can result in loss of energy. So body weight has little to do with power but only in increasing racquet head speed. If the racquet head makes a perfect elastic collision without twisting or any similar loss of energy, the ball retains or gains kinetic energy. Therefore the racquet must be gripped for stability at contact so it's an efficient stroke. Therefore, significant body weight with an improper grip will result in a poor hit. Stiffer racquets can conserve kinetic energy better but many people don't like those frames since shock on more flexible racquets is absorbed by the racquets but with a stiff racquet, shock is absorbed by the body (e.g, elbow).

A heavy ball vs a fast ball are also two different concepts. You have two types of forces on the ball: translational energy and rotational energy. A ball might rotate at 1,000 rpm and have an angular moment of inertia. The inertia and rotation create rotational energy. Translational energy (=1/2mv^2) is like a car moving forward or how we measure the speed of a tennis serve. However, if two serves are moving at 100 mph and one rotates 1,000 rpm
(=1/2x.0057kgx160x1000m/3600sx1000m/3600s + 1,000/sx1,000/sx.0057kgx0.033m...blah, blah) and the other at 4,000 rpm, the latter has significantly more total energy.
Or a ball moving at 100 mph and 500 rpm will probably have less energy than a ball at 90 mph and 3,000 rpm (you would need to calculate the inertia which can be a "moving" target). When a heavily spun ball moving let's say at 70 mph and 3,000 rpm hits the ground, it appears to jump since ground frictional forces increase the rotational energy.

Or at least, you can grasp the concepts....

[10splayer]

What about body weight going into the ball? Racket alone isn't much mass.
Tilden: "'Speed' is the actual rate with which a ball travels through the air. 'Pace' is the momentum with which it comes off the ground. Pace is weight. It is the 'sting' the ball carries when it comes off the ground, giving the inexperienced or unsuspecting player a shock of force which the stroke in no way showed."

Racquet head mass isn't much, except in comparison to the ball.

[10splayer]

Other variables are:
1.strings ( tension,hybrid/no hybrid,gauge,texture,how powerful chosen strings are,etc)
2.a location of a ball on strings ( for example location vs a sweet spot)

Please ask some questions and I can expand above

Julian, would you say that '"weight transfer" is synonomous with linear momentum?

[bottle]

I'm not Julian but think that one can crank weight onto the ball with body turn as well. Or do both. Or neither. A neutral shot in which one got all one's weight on front foot early, as Peter Burwash used to preach, and in which hips and shoulders had already done their thing might still be a great shot if all the force successfully multiplied into racket head speed for a weightless and purely topspun buggy-whip.

[tennis_chiro]

Think Different!

Everyone gets a little confused about linear vs angular momentum. In reality it's about levers and fulcrums and the force you can apply or should we say, more specifically, effective lever arms. Then we get into force created at right angles to the extended lever arm or lesser forces when the target line is less than 90 degrees from the vector of the lever arm.

The ball doesn't know how heavy or strong the person holding the racket is. It only knows about the force and momentum at the contact point. After all, how did little Justine Henin serve 117 mph and at almost twice the weight and an effective lever arm probably a good third greater, Isner cannot serve 1/3 faster (or anyone else for that matter).

Then we can get into all kinds of discussions about the length of the racket (27") and the length of the sword used by the Roman empire (27"). There was a big effort a few years ago to go to longer rackets. I got a set off Tom Gorman playing with a 15 ounce, 5 inch grip Wilson T2000 in 1968 (at 6', 165 lbs and not particularly strong). Budge even played with a 16 ounce club! But now rackets are generally around 11 or 12 ounces for the male pros and 13 ounces is a very heavy racket. I play with a 10 ounce racket. Most players play with grip sizes we would not have even considered possible in the 60's.

I posted a piece on this forum a couple of months ago about imagining hitting the ball with another ball on a string. Perhaps a better image to understand the importance of getting your weight forward to hit the ball solid would be to consider the difference between hitting something with a very heavy stick maybe 5 feet long, say a 4x4, or a small round ball of the same weight at the end of a 5 foot rope that you could swing like a mace (or the hammer throw in modern track and field). You can create a lot of force with that 4 x 4, but I'll take the mace for doing real damage. Now, think what happens when that mace is swung into its intended target. Would you think you got more effective force by jumping in the direction of the intended force as the mace was approaching impact; or would you actually try to stay very stable as you pulled against the rope that is trying with it's centripetal/centrifugal force to pull you off your position.

We don't work with loads and implements that are that heavy, but because of the great speeds, the forces are much greater than people recognize. The basic physics principles don't go away. They are just harder to see. The human body is an amazing machine. It can "cheat" physics…up to a point. But in the end, "cheating" those principles will take its toll… in injuries, inconsistency, inaccuracy, less power and, yes, losses.

What did Jobs say? "Think different!"

don

[julian1]

Yes

Julian, would you say that '"weight transfer" is synonomous with linear momentum?

Yes

[tennis_chiro]

Any response? Anybody?

Everyone gets a little confused about linear vs angular momentum. In reality it's about levers and fulcrums and the force you can apply or should we say, more specifically, effective lever arms. Then we get into force created at right angles to the extended lever arm or lesser forces when the target line is less than 90 degrees from the vector of the lever arm.

The ball doesn't know how heavy or strong the person holding the racket is. It only knows about the force and momentum at the contact point. After all, how did little Justine Henin serve 117 mph and at almost twice the weight and an effective lever arm probably a good third greater, Isner cannot serve 1/3 faster (or anyone else for that matter).

Then we can get into all kinds of discussions about the length of the racket (27") and the length of the sword used by the Roman empire (27"). There was a big effort a few years ago to go to longer rackets. I got a set off Tom Gorman playing with a 15 ounce, 5 inch grip Wilson T2000 in 1968 (at 6', 165 lbs and not particularly strong). Budge even played with a 16 ounce club! But now rackets are generally around 11 or 12 ounces for the male pros and 13 ounces is a very heavy racket. I play with a 10 ounce racket. Most players play with grip sizes we would not have even considered possible in the 60's.

I posted a piece on this forum a couple of months ago about imagining hitting the ball with another ball on a string. Perhaps a better image to understand the importance of getting your weight forward to hit the ball solid would be to consider the difference between hitting something with a very heavy stick maybe 5 feet long, say a 4x4, or a small round ball of the same weight at the end of a 5 foot rope that you could swing like a mace (or the hammer throw in modern track and field). You can create a lot of force with that 4 x 4, but I'll take the mace for doing real damage. Now, think what happens when that mace is swung into its intended target. Would you think you got more effective force by jumping in the direction of the intended force as the mace was approaching impact; or would you actually try to stay very stable as you pulled against the rope that is trying with it's centripetal/centrifugal force to pull you off your position.

We don't work with loads and implements that are that heavy, but because of the great speeds, the forces are much greater than people recognize. The basic physics principles don't go away. They are just harder to see. The human body is an amazing machine. It can "cheat" physics…up to a point. But in the end, "cheating" those principles will take its toll… in injuries, inconsistency, inaccuracy, less power and, yes, losses.

What did Jobs say? "Think different!"

don

I really thought this was a good post and it would get a response and spark some more discussion. Anyone?...I've been wrong before and will be again, but...

don

[bottle]

I've always preferred maces to Macy's but maybe just to think about them. I really liked this when I first read it because it reminded me of the old advice of Peter Burwash to get on front foot early rather than hit the ball while you're stepping across a short bridge.

The bridge idea seemed to involve the linear transfer of weight just as you hit the ball. There was a girl in our club who hit the ball that way, and her strokes looked beautiful in practice but didn't hold up when someone was jerking her around.

Because, as Burwash argued, she would never have the same amount of weight going through or wouldn't know how much.

But you're providing an added argument, it seems to me, that you can sling better if the fulcrum's in a single place-- to keep the string or rope or chain taut.

I must confess I've only been pursuing this idea recently in one hand backhands but see here you're referring to serve and forehands as well.

It's a very useful post, so thanks for it and Happy Holidays.

[stotty]

I really thought this was a good post and it would get a response and spark some more discussion. Anyone?...I've been wrong before and will be again, but...

don

Once we get into physics and geometry, I tend to get lost.

What this website needs (all on one place) is a section that explains (with diagrams), angular momentum, linear momentum, supination, external rotation, internal rotation, pronation, etc., etc., etc..

Some of these terms are obvious and standard knowledge to many of us but I can tell you that there is confusion amongst coaches about the exact meaning of some terminology. You ask coaches over here in the UK about linear momentum and you'll get different answers from each...one coach I spoke to thought it was a German phrase and had no idea what it meant!

[julian1]

For Don

Don,
your quote
--->
I posted a piece on this forum a couple of months ago about imagining hitting the ball with another ball on a string.
--->
Could you provide a link,please