Great Jack Kramer says lighter racquet so more power

Discussion in 'Tennis Tips/Instruction' started by boramiNYC, May 1, 2012.

  1. boramiNYC

    boramiNYC Hall of Fame

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    in the recent Lacoste commercial..

    There must be something about lighter racquet resulting in more power but this sounds so wrong in this forum. What gives?
     
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  2. olliess

    olliess Semi-Pro

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    It does result in more power if you've been using a racquet that's too heavy.
     
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  3. boramiNYC

    boramiNYC Hall of Fame

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    so, practice with a little heavier racquet and for match play use lighter one? I always felt my swing speed increase right after switching to lighter frame. But, I don't know if my balls are any heavier or lighter on the other side of the court.
     
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  4. sureshs

    sureshs Bionic Poster

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    He must have been paid to say it
     
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  5. boramiNYC

    boramiNYC Hall of Fame

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    Out of all people, I thought you would give 100% support to such a great champion as Jack.

    He sounds pretty sincere and with conviction the way he says it. BTW, he's talking about 'lighter' steel racquet Connors used compared to heavier wood frames.
     
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  6. sureshs

    sureshs Bionic Poster

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    Sorry I did not see the ad. Somehow I got confused and thought Lacoste makes rackets. It is Adidas who tried to get into rackets.
     
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  7. boramiNYC

    boramiNYC Hall of Fame

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    The ad says Mr. Lacoste invented the steel racquet and sold it to Wilson, and Jack Kramer, being a Wilson figure, talking about it.
     
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  8. 5263

    5263 G.O.A.T.

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    Probably meaning lighter than the wood rackets he played with.
    Only the strongest and best could swing those fast and controlled,
    is how many feel.
     
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  9. SystemicAnomaly

    SystemicAnomaly G.O.A.T.

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    The lighter racquet might possibly yield more power if you can swing it sufficiently faster than a heavy one. Or string it looser. Overall tho', heavier racquets have more power potential than light ones.


    Some time back there was a Sports Science episode that dealt with this. The feeling that you are swinging faster with the lighter racquet right after swinging a heavy one is an illusion -- "feel" and real are not necessarily the same is a conclusion of their experiment. The heavier racquet will actually train your muscles to swing slower and can throw your timing off for a while. If the heavier racket has a weight or swingweight that is 20% greater than your normal racquet, you may also be altering your swing mechanics too much.

    You might try Overload-Underload training. Swing with a racquet that has a 15% greater weight (or swingweight) for a while to develop a bit more muscle strength. Then switch to one that is 15% less than you regular racquet to work on a faster swing speed. You can perform shadow swings with an unstrung racquet to simulate one that is 15% lighter. Finally, switch back to your normal strung racquet to make sure that you've got your timing back.
     
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  10. 5263

    5263 G.O.A.T.

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    Sounds like good advice.
     
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  11. gameboy

    gameboy Hall of Fame

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    Look, it is simple physics. Lighter the racquet, faster you will swing. Faster you swing, the faster the ball will travel back, thus more power.

    The pro's use heavier racquets because the opponents hit very powerful shots and the racquets twist more. So sacrificing a little on racquet head speed is more than compensated by added stability.

    There is no reason why rec players should use such heavy frames (if you want more power). The guys around here use heavy frames because pros do it, not because they really need to. If pros started going towards lighter racquets, everyone here will too.

    There is a good reason why golf drivers have gotten lighter and lighter every year. It is because lighter clubs produce faster swing speeds. It is no different for tennis.
     
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  12. 5263

    5263 G.O.A.T.

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    First sentence is just not true. It's not a linear progression. Make racket .2oz lighter and I may or may not swing faster. I may already be swinging as fast as in can control with the slightly heavier stick, so making it any lighter won't bring more benefits.
     
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  13. SystemicAnomaly

    SystemicAnomaly G.O.A.T.

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    ^^ No gameboy, it's not that simple. I teach plenty of kids who have junior rackets that are very light. They can swing these very fast. At some point in their development, I have them hit with one of my 11 oz (medium poweer) rackets. Most of these kids will have significantly more power with the heavier racket than their sub-9 oz racket.
     
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  14. Timbo's hopeless slice

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    the one thing we can say with confidence is that it really isn't 'simple physics'

    I have a feeling that more mass equals more power at the same swing speed, but I could very easily be wrong. I play best and hit my heaviest shots with a frame around 12 oz, but this is such a personal thing!
     
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  15. Timbo's hopeless slice

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    actually, that's true. My 12 year old plays with Volkl 4s but every now and then has a hit with one of my Yonexs. He hits a much heavier ball with the Yonex but can't swing it effectively for long and really struggles to serve.
     
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  16. gameboy

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    Nope. You will swing faster with 0.2 oz ligher racquet. You just won't notice it because your swing is inconsistent and the difference in speed is negligible. But if you properly measure your racquet speed over many many swings, you will see the difference.
     
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  17. 5263

    5263 G.O.A.T.

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    I am pretty sure what you are saying can be right, but most certainly is not always the case.
    Anyway, if you can't notice it, it doesn't matter too much does it.
     
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  18. gameboy

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    That is because lighter racquet will twist more if you do not hit the sweetspot and lose speed. If the child hits the sweetspot every time, the child will generate more speed with the lighter racquet.

    There is a reason why tennis racquets have gotten lighter over the years, even with the pros. The golf drivers have gotten lighter even faster because you can more consistently hit the sweetspot with the golf clubs than you can with tennis.
     
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  19. gameboy

    gameboy Hall of Fame

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    No, you are not going to notice the difference much when you are talking about an ounce or so difference.

    Which is why some of the discussions around here about customizations are kinda ridiculous.
     
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  20. Cheetah

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    do you play tennis?
     
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  21. dennis10is

    dennis10is Banned

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    I'm sure you know the truth and everybody do not.

    I worship you.
     
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  22. theblueark

    theblueark New User

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    Gameboy you're assuming we swing at full speed on every stroke? What about volleys then? Lighter or heavier for more powerful volleys?
     
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  23. 1HBH Rocks

    1HBH Rocks Semi-Pro

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    Very simple equation... we try to maximize swinging speed when we know two things:
    -there's a limit to the speed at which you can contract your muscles;
    -what you exert is muscular tension (power) over a period of time (we transfer kinetic energy, not speed).

    So, you should be using as heavy a racket as you can to optimize swinging speed without compromising on the heft part of the equation (half the mass times square velocity equals energy).
     
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  24. Limpinhitter

    Limpinhitter Legend

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    Of course your right. Even a quantitatively challenged individual such as myself can understand that if two racquets are traveling at the same velosity, the racquet with more mass will transfer more energy to the ball. Similarly, if two racquets have the same mass, the one that is traveling at a higher velosity will transfer more energy to the ball.
     
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  25. Limpinhitter

    Limpinhitter Legend

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    Hahaha! You beat me to it.
     
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  26. LeeD

    LeeD Bionic Poster

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    Don't forget, we are NOT all equal.
    Some of us have great slow twitch muscles. Some of us have great fast twitch muscles.
    Some of us hit better with a slower swing.
    Some of us hit better with a faster swing.
    Some of us play against fast moving incoming balls.
    Some of us play against slower moving incoming balls.
    Some of us need more power, always.
    Some of us don't need more power, usually.
    Some of us think we play better with heavier rackets.
    Some of us dink we play bette wid lighter rackets.
    In reality, we play like we play, regardless of racket. Basically, because we're not on the tour, we all suck and obsess with what weight and balance, size and color, string gauge, grip material, size, head shape, polarization or not, whatever, we suck because we don't play tennis very well.
     
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  27. gameboy

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    Saying 1+1=2 isn't exactly declaring that one knows everything...
     
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  28. gameboy

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    Well, that may be common sense, but it is not physics.

    Here is the actual physics. Simple enough for most here to understand.

    When two objects collide, you have conservation of momentum:

    (m1 * v1) + (m2 * v2) = (m1 * u1<speed after collision>) + (m2 * u2)

    If you know the v1 and v2 (initial velocity of ball and racquet), you can solve for u1 and u2. And when there is a great difference between the mass of one object (racquet + body weight) over the other (tennis ball), the equation for u1 and u2 simplifies to this:

    u1 (racquet head speed after collision) = v1 (racquet head speed before collision)

    This means that the racquet sees no discernible loss of speed as it collides with the tennis ball.

    u2 (ball speed after collision) = (2*v1)-v2 (ball speed before collision)

    Of course this is not exact. The body-arm-racquet is not a perfectly ridgid body and there is also coefficient of restitution that will decreased the speed, but this is pretty much how it works. The main driver for the speed of the ball bouncing back from the racquet is the speed of the racquet head.

    Golfers have known this for a long time, which is why the drivers have gotten lighter and lighter to increase the swingspeed and thus increase the ball speed. And they have a room full of physicists working on them. Not just bunch of Internet posters with limited physics knowledge.

    The main benefit for heavier racquet is plowthrough. Because of extra mass, the racquet will not twist as much when you hit off center, which will result in smaller loss of velocity compared to hitting off-center with a much lighter racquet (and straighter too). Some people may equate that to being "more powerful" which I can understand. But that still does not change the fact that when all things are equal, the lighter racquet will produce faster swing and thus faster ball off the racquet.
     
    Last edited: May 1, 2012
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  29. Bobby Jr

    Bobby Jr Legend

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    Darn. Simple physics from the back of a box of fruit loops you mean? :lol:
     
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  30. olliess

    olliess Semi-Pro

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    Except that this isn't an adequate approximation for the tennis racquet-ball collision, as shown in published physics papers and in high speed film capture.

    Don't presume too much about your fellow Internet posters. Some of us have day jobs, too. ;)
     
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  31. 1HBH Rocks

    1HBH Rocks Semi-Pro

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    A 2oz ball versus a 10,5 to 12,5oz racket is a little less than 1 for 6 on average... I don't know if you can call that negligible. It brings the question of what's a great difference and if the simplification could be problematic when considering other factors.
     
    Last edited: May 1, 2012
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  32. gameboy

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    Can you link to the papers? I have read a lot of physics papers related to tennis and I have not read this...
     
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  33. 1HBH Rocks

    1HBH Rocks Semi-Pro

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    What is full speed? It's as fast as you can, but the movement you use is necessarily a binding condition -- you will also swing your volley as fast as a manageable volley can be swung if you're going to maximize power here too and, then, you'd compare two slower swings (volleys) against one another.

    You lighter frame will have you swing faster, your heavier frame will bring more heft. I am ready to grant our scientist on here my total agreement for one point without question: greater weight reduces the chances of issues associated with off center hits and over a big sample of swing, you might be in the end hitting harder with the heavier one since all your off center hits will produce greater results.
     
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  34. gameboy

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    That would be true if you threw the racquet at the ball.

    You are holding the racquet (pretty tightly I might add - even when you think you are holding it light, you can see the strain in the forearm and wrists in slow motion videos of pros) and that means that your weight gets added as well.

    As I have said earlier, it is a not a perfectly rigid body, but it is not just a racquet flying in space by itself either. If you count just fraction of your weight, say 10 or 15 pounds, you are getting closer to 1:100 or more weight ratio compared to the ball. At that point, the above equation would be a good proximation.
     
    Last edited: May 1, 2012
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  35. Timbo's hopeless slice

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    Your model assumes the ball to be essentially a static object (like a golf ball), this is rather obviously not the case.

    The racquet is not the only element with momentum...
     
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  36. 5263

    5263 G.O.A.T.

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    do you feel F=MA applies to this at all?
     
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  37. Timbo's hopeless slice

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    there you go, it's simple!!!
     
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  38. sureshs

    sureshs Bionic Poster

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    I don't see this happening as it requires the racket mass to be much higher than the ball mass. Much greater than means at least 10:1, so you would need at least a 20 oz frame to see this effect.

    This is how to analyze it, assuming such linear collision models are really true, because these days there is enormous angular momentum:

    m1*v1 - m2*v2 = m1*u1 + m2*u2, where v1 has its sign reversed as the ball is moving initially opposite to the direction the racket is moving, and both of them will move in the direction of the racket after collision.

    Let us say our expectation is to at least "reflect" the ball back at the same velocity, i.e. match the groundstroke speed. Then u2 = v2.

    m1*(v1 - u1) = 2*m2*v2

    m1/m2 = 2*m2*v2/(v1 - u1)

    For your assumption that v1 = u1 to be true, m1 must approach a value infinitely greater than m2! Since a ratio of 1:6 does not cut it, therefore the assumption that v1 = u1 is not correct.

    Edit: you are including part of the body weight in m1. Hmmm. Then you might actually be right.

    In fact, now that I think about it, except for a slight wobble, the racket does not seem to lose much speed after impact in high speed video.
     
    Last edited: May 1, 2012
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  39. sureshs

    sureshs Bionic Poster

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    Netzroller's conclusion can even more simply derived like this:

    The kinetic energy is 0.5*m*v^2

    Anything quadratic will end up dominating anything linear. So, increasing swingspeed will give more power than increasing mass, after a certain point.

    This even works for angular motion. Kinetic energy = 0.5*I*omega^2, but omega (angular velocity) = v (linear velocity)/radius, so either v or omega is still a quadratic term. I is moment of inertia.

    The most critical question is: when does increasing m starts giving diminishing returns and increasing v or omega is better. Since speed is difficult to achieve higher the mass, there is a critical point at which the player is better off not going for a heavier frame, but swinging the existing frame faster.

    For the ATP pros, it is between 12 and 12.5 oz these days.
     
    Last edited: May 1, 2012
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  40. sureshs

    sureshs Bionic Poster

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    Yes it does. That is why my post, gameboy's post, and netzroller's analyses are all wrong.

    Momentum is conserved only when there is no net external force. For the case of billiard balls, which is the model everyone is using, gravity is canceled by the normal reactions from the table. Another way of expressing it is that momentum is conserved in one direction only if there is no net force in that direction.

    In tennis, the hand accelerates the racket, and continues to exert a force pulling the racket through impact.

    So any analysis using conservation of momentum is wrong.

    Edit: darn it is not simple. Gameboy is including the body in m1. If you do that, since the body is supplying the force, it can be argued that there is no net external force, so these analyzes are not far from the mark.
     
    Last edited: May 1, 2012
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  41. 5263

    5263 G.O.A.T.

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    and here was the whole point-

    "Therefore, if a light racket allows you to swing faster, you will be able to hit harder.
    Unfortunately, these equations can still not tell you, what racket you should use.
    In order to draw more conclusion from this, one would need to know more on the bio-mechanical background: Can the body rather move heavier things slow or light things fast? What feels more comfortable and which speed can be coordinated best? How does performance drop over the course of a match? At what point does racket weight get in the way of your mechanics?"
     
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  42. Timbo's hopeless slice

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    fixed it for you :)

    basically, the fact remains that, for a given swing speed, heavier racquets hit harder.

    How fast an individual can actually swing one, of course, is by far the most significant variable...
     
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  43. boramiNYC

    boramiNYC Hall of Fame

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    Thanks slice, that made a lot of sense. I agree with that poster's conclusion and it seems the not too uncommon advice of 'heaviest racquet you can swing fastest' is a pretty accurate answer. But, at some point maneuverability and individual game style also become factor.
     
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  44. boramiNYC

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    I'd think the conservation of momentum is pretty universal and it should apply as well. But, definitely not the only model that can explain this collision.
     
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  45. SystemicAnomaly

    SystemicAnomaly G.O.A.T.

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    For a given swing speed, a heavier racquet or one with a higher swingweight, in general, should produce more power. Perhaps we should be talking about swingweight rather than static weight here:

    http://twu.tennis-warehouse.com/learning_center/specsandspeed.php

    As suresh and others have indicated, rackets are typically 5 to 6x the mass of the ball. The assumption that the racket does not lose speed due to impact simply is not true. When a ball bounces on the ground, however, we can assume that the Earth does not lose too much speed due to the collision. TWU physicist, Rod Cross and others indicate that the angular velocity of the racket drops significantly. Here is another physics link that shows this:

    http://www.science-animations.com/support-files/tennis.swf

    This animation comes from the following page on tennis biomechanics:

    http://www.science-animations.com/tennismechanics.html
    .
     
    Last edited: May 1, 2012
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  46. sureshs

    sureshs Bionic Poster

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    I edited my post.

    But no, being universal has nothing to do with satisfying the condition under which it is universal.
     
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  47. boramiNYC

    boramiNYC Hall of Fame

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    This must be what creates the feel of 'plow through'. Less velocity drop from impact.

    However, since the velocity just before contact is most important, the velocity drop shouldn't matter too much.
     
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  48. boramiNYC

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    More importantly how fast an individual can actually swing one 'with control' would be key. :)
     
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  49. theblueark

    theblueark New User

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    In a reflex volley or block volley, let us assume the racquet is essentially not moving.

    In your model because you assume u1 = v1, both racquets will stay dead where it is at contact due to out body holding onto the racquet in a death grip and u2 will = v2?
     
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  50. gameboy

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    This is true, but you WILL swing a lighter racquet faster, so you will get more power from a lighter racquet (all other things being equal).

    Which is why Jack is correct.
     
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