Você Tem Ideia Qual é a Força Aplicada na Sua Raquete Durante Um Jogo
de Tênis?
Provavelmente Não e Vai se Surpreender Com os Resultados Que Vou lhe Apresentar.
Se Acha Que a Força é Desprezível, Então Não Leia Esse Artigo!
Olá tenista!
Segundo o site da ITF - International Tennis
Federation, oficialmente existem quatro tipos de bolas, 1, 2, 3 e High Altitude
(Altitude Elevada) e todas essas bolas devem pesar entre 56,0 e 59,4 gramas. A
ITF não define qual são os erros aceitáveis de medida, mas isso não interferirá
em nossos cálculos.
Para nossas avaliações, vamos utilizar os dados compilados por Simon Goodwill, engenheiro aeronáutico inglês e referência mundial na área de pesquisa em eventos físicos no esporte. Goodwill possui doutorado e é Diretor do Centre for Sports Engineering Research (CSER) da Sheffield Hallam University situada na Inglaterra.
Goodwill et al. publicou há anos atrás um gráfico demonstrando qual o tempo que uma bola de tênis permanece em contato com a raquete durante o impacto entre ambas.
O gráfico abaixo demonstra os tempos que ocorrem em duas situações distintas onde as mesmas raquetes apresentam tensões de encordoamentos diferentes, 40 lb (libras) e 70 lb (libras).
Para nossas avaliações, vamos utilizar os dados compilados por Simon Goodwill, engenheiro aeronáutico inglês e referência mundial na área de pesquisa em eventos físicos no esporte. Goodwill possui doutorado e é Diretor do Centre for Sports Engineering Research (CSER) da Sheffield Hallam University situada na Inglaterra.
Goodwill et al. publicou há anos atrás um gráfico demonstrando qual o tempo que uma bola de tênis permanece em contato com a raquete durante o impacto entre ambas.
O gráfico abaixo demonstra os tempos que ocorrem em duas situações distintas onde as mesmas raquetes apresentam tensões de encordoamentos diferentes, 40 lb (libras) e 70 lb (libras).
Fonte: Goodwill, S.R., & Haake, S. (2004). Effect of string tension on the impact between a tennis ball and racket. In Hubbard, M., Mehta, R.D., & Pallis, J.M. (Eds.) The engineering of sport 5. (pp. 3-9). International sports engineering assocation
Com base nos dados acima, temos
duas informações importantes: pesos das bolas e tempos que as mesmas permanecem
em contato com o encordoamento no momento do impacto.
Podemos então aplicar a Segunda
Lei de Newton que determina que F = m.a ou Força = massa x aceleração.
Utilizando a fórmula no nosso
exemplo, temos que:
Força = massa da bola x
aceleração da bola.
Ocorre que aceleração é dada pela
expressão:
Nesse caso vamos considerar
que massa e peso são elementos iguais. Eles não são, mas para nossos cálculos
não haverá qualquer interferência.
No futuro poderemos
discorrer sobre a diferença entre massa e peso.
O gráfico proposto por
Goodwill nos informa que o tempo mínimo de contato entre a bola e a raquete é
de 3 ms (milissegundos) e o máximo de 5 (milissegundos) mesmo com
encordoamentos e tensões diferentes.
Com essas informações
podemos calcular qual é a força aplicada na raquete durante um golpe na prática
do tênis.
Vamos a título de hipótese,
estipular que a velocidade da bola na raquete seja de 30 m/s ou 108 km/h. É uma
bola típica de lançamento quando se inicia um aquecimento.
Aplicando-se a Segunda
Lei de Newton teremos:
Massa da bola: 56,0 g (mínimo)
Tempo de contato com a bola: 3 ms (mínimo)
Velocidade de saída da bola na
raquete: 30 m/s (108 km/h)
Assim sendo teremos:
Observe que dividi 56,0 por mil, pois estamos aplicando quilogramas e 3 dividido por mil transformado em segundos, pois elegemos o sistema MKS (metro, quilograma e segundo).
Vamos transformar
newtons em kgf e verificar o que ocorre:
Os 57,17 kgf são aplicados na sua raquete num simples lançamento de uma bola!
Pois é, mas ainda não
terminei de contar todos os fatos!
Esses cálculos só valem
para uma bola lançada com velocidade inicial igual a zero e acelerada a 30 m/s
na raquete e não numa rebatida de uma bola acelerada pelo seu oponente!
Será que uma bola rebatida por seu adversário e vindo em sua direção aumenta ou diminui a força
aplicada na sua raquete?
É isso que vamos
analisar a seguir.
Vamos supor que a bola de seu
oponente impacte sua raquete a 70% da velocidade de lançamento de 30 m/s, pois ao longo do percurso entre seu oponente e você
haverá perda de energia ocasionada pelo atrito ou arrasto entre a bola e o
ar e também entre a bola e a quadra no momento em que ela tocar o solo.
A situação agora é outra, pois
teremos a velocidade da bola de retorno do oponente a 21 m/s (30 m/s x 70%) contra
sua raquete que estaria projetando a bola a 30 m/s e o somatório das
velocidades nos daria 51 m/s (30 + 21) que aplicados na fórmula teríamos:
Mais assustador ainda, cerca de 88 kgf agindo sobre a minha raquete!
Podemos observar que houve um incremento da ordem de 54,75% nos impactos entre o primeiro caso e o segundo, o que é significativo.
E
qual seria a força reagindo na raquete num saque a 200 km/h?
Temos:
Massa da bola: 56,0 g
Tempo de contato com a bola: 3 ms
Velocidade de saída da bola na raquete:
55,56 m/s (200 km/h)
Sim, 104,00 kgf são aplicados na sua raquete em um saque a 200 km/h!
Agora
você começa a entender porque os tenistas têm tantas lesões no punho, cotovelo,
ombro, coluna, quadril, joelho e tornozelo.
A
primeira Lei da Termodinâmica é implacável: energia não pode ser criada ou
destruída, apenas transferida. Os 104,00 kgf aplicados na sua raquete são
transferidos para o seu corpo e os resultados não são dos melhores.
Note que os 88,47 kgf calculados para velocidades relativamente baixas, não são muito diferentes de um saque potente executado por um profissional. A diferença é da ordem de 17,55% entre ambos, não muito expressiva, mas a percepção que temos é outra.
Não podemos deixar de mencionar que quanto menos tempo a bola se mantiver na raquete, maior será a força aplicada na mesma.
Isso tem enormes implicações no jogo de cada tenista, pois em função do tipo de encordoamento utilizado e a pressão aplicada no mesmo, as respostas serão totalmente distintas.
Não podemos deixar de mencionar que quanto menos tempo a bola se mantiver na raquete, maior será a força aplicada na mesma.
Isso tem enormes implicações no jogo de cada tenista, pois em função do tipo de encordoamento utilizado e a pressão aplicada no mesmo, as respostas serão totalmente distintas.
Poderíamos
fazer inúmeras simulações com diversas velocidades e tempos de contato da bola com a raquete, mas
isso pode ficar para outro capítulo.
Com as equações demonstradas nesse artigo, os leitores do blog poderão calcular quaisquer esforços solicitantes apenas ajustando o tempo de contato da bola na raquete bem como sua velocidade de saída.
Infelizmente as informações acima não são divulgadas pela comunidade tenística basicamente por dois motivos: total desconhecimento de como calcular os esforços solicitantes ou desinteresse para não prejudicar o esporte que no mundo fatura bilhões de dólares anualmente.
A percepção que se tem nas duas alternativas é que nossa saúde no contexto é irrelevante.
Os resultados calculados demonstram claramente a importância de um trabalho anaeróbico severo, no caso musculação, para fortalecimento das áreas do corpo que são acionadas milhares de vezes ao longo dos treinos e partidas.
E isso vale para jogadores principiantes, intermediários, avançados e profissionais.
Essa questão é complexa pois se os músculos forem enrijecidos em demasia, haverá perda de flexibilidade dos mesmos e a dinâmica dos golpes será prejudicada.
Se os músculos não forem fortalecidos adequadamente, fatalmente sofrerão danos pelo elevado esforço exigido, além das milhares de repetições dos golpes.
Eis aí um bom artigo para ser publicado por alguém efetivamente capacitado na área. Com a palavra os fisiologistas, preparadores físicos, fisioterapeutas e áreas correlatas.
Quando alguém disser para você que tênis não é “força”
e sim “jeito”, pergunte, você tem um "tempinho"?
Um forte abraço
Franco Morais
www.tenniscience.com.br
Do You Have Any Idea What Force is Applied to Your Racket During a Tennis Game?*
Probably not and you will be surprised by the results I am going to present you.
If You Think Strength Is Despicable, Then Don't Read This Article!
Hello tennis player!
According to the ITF - International Tennis Federation website, there are officially four types of balls, 1, 2, 3 and High Altitude, and all of these balls must weigh between 56.0 and 59.4 grams. The ITF does not define what are the acceptable measurement errors, but this will not interfere with our calculations.
For our evaluations, we will use the data compiled by Simon Goodwill, an English aeronautical engineer and a world reference in the field of research in physical events in sport. Goodwill holds a doctorate and is Director of the Center for Sports Engineering Research (CSER) at Sheffield Hallam University in England.
Goodwill et al. published a graph years ago showing how long a tennis ball stays in contact with the racket during the impact between them.
The graph below shows the times that occur in two different situations where the same rackets have different strand stresses, 40 lb (pounds) and 70 lb (pounds).
www.tenniscience.com.br
Do You Have Any Idea What Force is Applied to Your Racket During a Tennis Game?*
Probably not and you will be surprised by the results I am going to present you.
If You Think Strength Is Despicable, Then Don't Read This Article!
Hello tennis player!
According to the ITF - International Tennis Federation website, there are officially four types of balls, 1, 2, 3 and High Altitude, and all of these balls must weigh between 56.0 and 59.4 grams. The ITF does not define what are the acceptable measurement errors, but this will not interfere with our calculations.
For our evaluations, we will use the data compiled by Simon Goodwill, an English aeronautical engineer and a world reference in the field of research in physical events in sport. Goodwill holds a doctorate and is Director of the Center for Sports Engineering Research (CSER) at Sheffield Hallam University in England.
Goodwill et al. published a graph years ago showing how long a tennis ball stays in contact with the racket during the impact between them.
The graph below shows the times that occur in two different situations where the same rackets have different strand stresses, 40 lb (pounds) and 70 lb (pounds).
Source: Goodwill, S.R., & Haake, S. (2004). Effect of string tension on the impact between a tennis ball and racket. In Hubbard, M., Mehta, R.D., & Pallis, J.M. (Eds.) The engineering of sport 5. (pp. 3-9). International sports engineering assocation
Based on the data above, we have two important information: weights of the balls and times that they remain in contact with the string at the moment of impact.
We can then apply Newton's Second Law which states that F = m.a or Force = mass x acceleration.
Using the formula in our example, we have to:
Force = mass of the ball x acceleration of the ball.
It happens that acceleration is given by the expression:
Therefore:
In this case we will consider that mass and weight are equal elements. They are not, but for our calculations there will be no interference.
In the future we will be able to discuss the difference between mass and weight.
The graph proposed by Goodwill informs us that the minimum contact time between the ball and the racket is 3 ms (milliseconds) and the maximum of 5 (milliseconds) even with different strings and stresses.
With this information we can calculate what is the force applied to the racket during a tennis hit.
Let's hypothesize, stipulate that the speed of the ball in the racket is 30 m / s or 108 km / h. It is a typical launch ball when a warm-up begins.
Applying Newton's Second Law we have:
Substituting the data we have:
Ball mass: 56.0 g (minimum)
Time of contact with the ball: 3 ms (minimum)
Speed of the ball on the racket after contact: 30 m / s (108 km / h)
To apply the equation, we have to use a dimensional system, in which case the MKS (meter, kilogram and second) will be chosen.
So we will have:
Note that I divided 56.0 per thousand, because we are applying kilograms and 3 divided by thousand transformed in seconds, because we chose the MKS system (meter, kilogram and second).
Let's convert newtons to kgf and see what happens:
Scary, isn't it?
The 57.17 kgf is applied to your racket in a simple throw of a ball!
Yeah, but I haven't finished telling all the facts yet!
These calculations are only valid for a ball launched with an initial speed equal to zero and accelerated to 30 m / s on the racket and not in a hit of an accelerated ball by your opponent!
Does a ball hitting your opponent and coming towards you increase or decrease the force applied to your racket?
That is what we will analyze next.
Let's suppose that your opponent's ball impacts your racket at 70% of the launch speed of 30 m / s, because along the path between your opponent and you there will be a loss of energy caused by the friction or drag between the ball and the air and also between the ball and the court when it touches the ground.
The situation is different now, as we will have the opponent's return ball speed at 21 m / s (30 m / sx 70%) against his racket that would be projecting the ball at 30 m / s and the sum of the speeds would give us 51 m / s (30 + 21) that applied in the formula we would have:
Even scarier, about 88 kgf acting on my racket!
We can see that there was an increase of 54.75% in the impacts between the first case and the second, which is significant.
And what would be the force reacting on the racket in a serve at 200 km / h?
We have:
Ball mass: 56.0 g
Time of contact with the ball: 3 ms
Speed of the ball in the racket after contact: 55.56 m / s (200 km / h)
Yes, 104.00 kgf are applied to your racket in a serve at 200 km / h!
Now you begin to understand why tennis players have so many injuries to the wrist, elbow, shoulder, spine, hip, knee and ankle.
The first Law of Thermodynamics is relentless: energy cannot be created or destroyed, only transferred. The 104.00 kgf applied to your racket is transferred to your body and the results are not the best.
Note that the 88.47 kgf calculated for relatively low speeds, is not much different from a powerful serve performed by a professional. The difference is of the order of 17.55% between both, not very expressive, but the perception we have is different.
We cannot fail to mention that the less time the ball remains on the racket, the greater the force applied to it.
This has enormous implications for the game of each tennis player, because depending on the type of string used and the pressure applied to it, the answers will be totally different.
We could do numerous simulations with different speeds and times of contact of the ball with the racket, but that can be for another chapter.
With the equations shown in this article, blog readers will be able to calculate any efforts just by adjusting the contact time of the ball on the racket as well as its outgoing speed.
Unfortunately, the information above is not released by the tennis community basically for two reasons: total ignorance of how to calculate the efforts or disinterest in order not to harm the sport that in the world earns billions of dollars annually.
The perception that we have in the two alternatives is that our health in the context is irrelevant.
The calculated results clearly demonstrate the importance of severe anaerobic work, in the case of weight training, to strengthen the areas of the body that are triggered thousands of times during training and matches.
And that goes for beginners, intermediate, advanced and professional players.
This issue is complex because if the muscles are too tight, there will be a loss of flexibility and the dynamics of the strokes will be impaired.
If the muscles are not strengthened properly, they will fatally suffer damage due to the high effort required, in addition to the thousands of repetitions of the strokes.
Here is a good article to be published by someone effectively trained in the field like physiologists, physical trainers, physiotherapists and related areas.
When someone tells you that tennis is not "strength" but "way or manner", ask, can we talk a little bit?
Best regards
Franco Morais
www.tenniscience.com.br
We can then apply Newton's Second Law which states that F = m.a or Force = mass x acceleration.
Using the formula in our example, we have to:
Force = mass of the ball x acceleration of the ball.
It happens that acceleration is given by the expression:
Therefore:
In the future we will be able to discuss the difference between mass and weight.
The graph proposed by Goodwill informs us that the minimum contact time between the ball and the racket is 3 ms (milliseconds) and the maximum of 5 (milliseconds) even with different strings and stresses.
With this information we can calculate what is the force applied to the racket during a tennis hit.
Let's hypothesize, stipulate that the speed of the ball in the racket is 30 m / s or 108 km / h. It is a typical launch ball when a warm-up begins.
Applying Newton's Second Law we have:
Substituting the data we have:
Ball mass: 56.0 g (minimum)
Time of contact with the ball: 3 ms (minimum)
Speed of the ball on the racket after contact: 30 m / s (108 km / h)
To apply the equation, we have to use a dimensional system, in which case the MKS (meter, kilogram and second) will be chosen.
So we will have:
Note that I divided 56.0 per thousand, because we are applying kilograms and 3 divided by thousand transformed in seconds, because we chose the MKS system (meter, kilogram and second).
Let's convert newtons to kgf and see what happens:
Scary, isn't it?
The 57.17 kgf is applied to your racket in a simple throw of a ball!
Yeah, but I haven't finished telling all the facts yet!
These calculations are only valid for a ball launched with an initial speed equal to zero and accelerated to 30 m / s on the racket and not in a hit of an accelerated ball by your opponent!
Does a ball hitting your opponent and coming towards you increase or decrease the force applied to your racket?
That is what we will analyze next.
Let's suppose that your opponent's ball impacts your racket at 70% of the launch speed of 30 m / s, because along the path between your opponent and you there will be a loss of energy caused by the friction or drag between the ball and the air and also between the ball and the court when it touches the ground.
The situation is different now, as we will have the opponent's return ball speed at 21 m / s (30 m / sx 70%) against his racket that would be projecting the ball at 30 m / s and the sum of the speeds would give us 51 m / s (30 + 21) that applied in the formula we would have:
Even scarier, about 88 kgf acting on my racket!
We can see that there was an increase of 54.75% in the impacts between the first case and the second, which is significant.
And what would be the force reacting on the racket in a serve at 200 km / h?
We have:
Ball mass: 56.0 g
Time of contact with the ball: 3 ms
Speed of the ball in the racket after contact: 55.56 m / s (200 km / h)
Yes, 104.00 kgf are applied to your racket in a serve at 200 km / h!
Now you begin to understand why tennis players have so many injuries to the wrist, elbow, shoulder, spine, hip, knee and ankle.
The first Law of Thermodynamics is relentless: energy cannot be created or destroyed, only transferred. The 104.00 kgf applied to your racket is transferred to your body and the results are not the best.
Note that the 88.47 kgf calculated for relatively low speeds, is not much different from a powerful serve performed by a professional. The difference is of the order of 17.55% between both, not very expressive, but the perception we have is different.
We cannot fail to mention that the less time the ball remains on the racket, the greater the force applied to it.
This has enormous implications for the game of each tennis player, because depending on the type of string used and the pressure applied to it, the answers will be totally different.
We could do numerous simulations with different speeds and times of contact of the ball with the racket, but that can be for another chapter.
With the equations shown in this article, blog readers will be able to calculate any efforts just by adjusting the contact time of the ball on the racket as well as its outgoing speed.
Unfortunately, the information above is not released by the tennis community basically for two reasons: total ignorance of how to calculate the efforts or disinterest in order not to harm the sport that in the world earns billions of dollars annually.
The perception that we have in the two alternatives is that our health in the context is irrelevant.
The calculated results clearly demonstrate the importance of severe anaerobic work, in the case of weight training, to strengthen the areas of the body that are triggered thousands of times during training and matches.
And that goes for beginners, intermediate, advanced and professional players.
This issue is complex because if the muscles are too tight, there will be a loss of flexibility and the dynamics of the strokes will be impaired.
If the muscles are not strengthened properly, they will fatally suffer damage due to the high effort required, in addition to the thousands of repetitions of the strokes.
Here is a good article to be published by someone effectively trained in the field like physiologists, physical trainers, physiotherapists and related areas.
When someone tells you that tennis is not "strength" but "way or manner", ask, can we talk a little bit?
Best regards
Franco Morais
www.tenniscience.com.br
