Indeed, but then you do start with your non-racquet foot forward and turn your hips and shoulders (jeez, let's rotate the entire body ) during the stroke don't you ? This produces ANGULAR momentum (whether it's a significant parameter or not is another manner)... Think ROTATIONAL physics, not LINEAR physics... Cheers, Mike
I may be interpreting this statement wrong but a continuous application of force/torque results in an increase in velocity and momentum (acceleration). Velocity and momentum will remain constant only in the absence of further torque... Cheers, Mike
I don't agree if you take it to the limit, an extremely flexible shaft would deflect no matter how short the impact time. Also the impact time is directly a function of string tension. Whilst this is theorectically correct, but simply because of the limitations of the human body you can say that heavier racquets will produce higher shuttle speeds if you have the strength to use them. Simply put you will eventually (with "perfect technique, etc) reach a maximum swing speed, ie that of your unladened arm, you won't be able to swing significantly faster regardless of how light your racquet is. For example comparing the acceration of you wrist with an unladened palm, to one holding a 10 gram weight and the difference would be almost unnoticable. However an extra 10 grams on the head of a racquet (assuming you are stronger enough to use it, ie say the difference between a 40 g and 50 g racquet [1]), for almost no difference in swing speed would cause significant improvement in shuttle speed. Where this differs from golf is that whilst in golf the head has a much higher mass moment of inertia around the pivot compared to the shaft, in badminton this is not so. [1] Racquet weights are for illustrative purposed only, I don't claim that there are any racquet this weight, however the theory holds regardless.
Pecheur, As ever, you mention excellent points. However, while I fully agree that more head weight will produce more shuttle speed ("assuming one is stronger enough to use it"), I do believe I mentioned an assumption of similar strength (i.e. "given a similar torque") I should also point out that you introduced an interesting additional parameter by mentioning "heavier racquets", something distinct from my "head-heavy" vs. "head-light" point. Cheers, Mike
Here are a couple of URLs to clear things up concerning the transfer of ANGULAR momentum I was referring to in my original post: http://www.bsu.edu/web/ykwon/pep294/notes/akin.html http://www.cwu.edu/~acquisto/NLangular.htm And here's a quote from the second URL above: "Angular momentum can be transferred from one body segment to the next. Since body segments differ in mass, the moment of inertia of each body will vary. Considering that momentum is conserved, a reduction in the moment of inertia of a body part will result in an increased angular velocity. The latter can be applied to throwing and kicking movements. For example, throwing involves a series of angular rotations of progressively lighter body segments (leg/trunk--arm). A reduction in moment of inertia between the leg/trunk complex and the lighter arm, results in an increased velocity of the arm." So we are really talking about momentum transfer...but of the angular (not linear) variety. A Google search with "angular kinetics" seems to yield useful sites. To summarize: An understanding of angular kinetics as they apply to badminton strokes (or any sport involving circular strokes) helps one understand why some players generate tremendous smash velocity in a seemingly effortless fashion. A proper sequencing of movements yields "free" velocity without undue muscular effort. Using golf as an illustrative example (because its easier to illustrate this point using the distance of a golf ball than the speed of a bird), proper use of angular kinetics also allow a 13 year old girl (Michelle Wie) to hit a golf ball close to 300 yards in a seemingly effortless fashion whereas big muscular guys manage only some 200 yards. Proper use of angular kinetics also explains why figure skaters spin faster by simply bringing arms and legs closer to the axis of rotation, why platform divers spin faster by going into a tuck while diving, etc. Cheers, MIke
Here are a couple of URLs to clear things up concerning the transfer of ANGULAR momentum I was referring to in my original post: http://www.bsu.edu/web/ykwon/pep294/notes/akin.html http://www.cwu.edu/~acquisto/NLangular.htm And here's a quote from the second URL above: "Angular momentum can be transferred from one body segment to the next. Since body segments differ in mass, the moment of inertia of each body will vary. Considering that momentum is conserved, a reduction in the moment of inertia of a body part will result in an increased angular velocity. The latter can be applied to throwing and kicking movements. For example, throwing involves a series of angular rotations of progressively lighter body segments (leg/trunk--arm). A reduction in moment of inertia between the leg/trunk complex and the lighter arm, results in an increased velocity of the arm." So we are really talking about momentum transfer...but of the angular (not linear) variety. A Google search with "angular kinetics" seems to yield useful sites. To summarize: An understanding of angular kinetics as they apply to badminton strokes (or any sport involving circular strokes) helps one understand why some players generate tremendous smash velocity in a seemingly effortless fashion. A proper sequencing of movements yields "free" velocity without undue muscular effort. Using golf as an illustrative example (because its easier to illustrate this point using the distance of a golf ball than the speed of a bird), proper use of angular kinetics also allow a 13 year old girl (Michelle Wie) to hit a golf ball close to 300 yards in a seemingly effortless fashion whereas big muscular guys manage only some 200 yards. Proper use of angular kinetics also explains why figure skaters spin faster by simply bringing arms and legs closer to the axis of rotation, why platform divers spin faster by going into a tuck while diving, etc. Cheers, MIke
transfer of angular momentum If I use a lighter racquet (vs. a heavy racquet), I can get a faster racquet angular velocity. ( I swear I notice the differences) Also I can imagine if i have a heavy chest (lot of muscle and FAT) and a BIG FAT belly, and transfer their angular momentum to arm and racquet, I can get a faster and harder smash.
Re: transfer of angular momentum Well, I imagine that one could model that McDonaldesque body as one big lever running from left hip to right shoulder (for a rightie) for the sake of simplicity. So, given that both momentum (angular or linear) and torque involve mass and velocity, i.e. (simple formula versions with equal mass distribution): Angular Momentum = (mass * lever length^2) * angular velocity Torque = (mass * lever length^2) * angular acceleration Two players (Skinny and Beefy) producing equal torque from their legs (or whichever other body parts are involved in applying torque to this lever) then Beefy's shoulder angular velocity would be proportionately less given the increase in mass. Now, how would both players' angular momenta compare ? Cheers, Mike
