Analysis and explanation of badminton ball speed
Because the killing speed is very fast, it takes less time to reach the opponent's court, leaving less time for the opponent to judge and shoot. Therefore, killing the ball will directly affect the quality and confidence of the opponent's return, which is a great threat to the opponent. How fast can you kill the ball? Fu Haifeng's highest record is a speed record of more than 332 km/h, while Dānlín, Taufik and Li Chongwei usually kill people at a speed of 220~270 km/h ... How fast can amateurs like us play ball? In addition to the basic movements should be in place reasonably, what other factors are related to the ball speed? Which factor is decisive?
What is the speed of badminton after being hit by a racket? First of all, we regard this collision as a completely elastic collision. Under this assumption, two conservation equations of momentum and kinetic energy are applied to solve the spherical velocity law at the same time, as follows:
Let the mass be m, the speed be v, the subscript of the racket be p, the subscript of the ball be q, and the superscript after hitting the ball be', then
According to the understanding in memory, racket, human and badminton constitute a system, in which human and racket constitute a subsystem. The quality of this system is far greater than that of a badminton with 5g, so we can apply the third special example in the book (P 13 1), that is, the quality Mq of badminton can be ignored, so A-2 can be written as:
Vq'=2Vp-Vq R- 1
We assume that the ball is suspended under a thin line to hit the ball, that is, when hitting the hovering ball (used by beginners in practice), Vq=0, and then we can draw the following conclusions:
Vq'=2Vp R-2
The understanding of this formula is that if the speed of the racket is 80km/h and the speed of the badminton is 160km/h, if the speed of the racket is 100 km/h and the speed of the ball is 200 km, this is still a considerable change. In other words, when killing the ball, you can't relax at all, just relax a little. As soon as the shooting speed is reduced, the speed of the ball will be reduced by two times, which has a great impact.
If you hit the ball in sports, Vq is not equal to zero, then the second term on the right of A-2 is -Vq (note the minus sign), and the first term is 2Vp, so the ball speed is:
Vq'=2Vp-Vq R- 1
R- 1 formula is the most common formula we usually use in wartime.
Through the conservation of momentum, the formula of collision speed is deduced. We know that the speed of the ball is mainly determined by the swing speed, which is the core theoretical basis of badminton speed. So when we play ball, we must strive to improve our shooting speed.
So what is the speed of the ball under real conditions? Or how fast do we shoot? Baseball and softball are similar to badminton in throwing strength and action mode, both of which are swing arms, so the shooting speed of these two sports should be equal. I looked up some information on the internet, most of which were softball. Although softball is only a women's event, it can also be used for reference because its posture and range are similar to badminton. The highest speed record of Chinese elite softball players is about 1 10 km/h, so badminton is 220 km. Huang Sui, a women's badminton doubles player, ran 257 km/h. Baseball (pure men's event) is said to be 170 km/h, which was measured by Americans. If it were badminton, it would be 340 km/h. Fu Haifeng, a male doubles player, broke the record of 332km/h, and the killing speed of excellent singles players is generally 260-300km/h. From the data, the speed of badminton is about twice that of baseball and softball.
But is this seemingly close double speed a fact? We can continue to analyze. Let me talk about the speed concept mentioned above. Hand speed refers to the speed of human hands, and ball speed refers to the speed at which baseball, softball and badminton leave their hands and rackets. Baseball and softball are separated by hands, so the speed of the two sports is the same as that of the hand, but badminton is different, it is the speed of the racket. Secondly, baseball, softball and badminton are all swing arm movements that rotate around the shoulder joint, so they are all rotating movements, so they all have angular velocity and linear velocity. Linear speed is proportional to radius (V=? *r, linear velocity = angular velocity * radius), in the same case, the greater the radius of rotation, the greater the linear velocity. Badminton needs a racket, so badminton is faster than softball players? Big? . According to the regulations, the length of badminton rackets should not exceed 68 cm, so our hands should extend about 70 cm. There is a certain relationship between human arm length and height, which is generally 65~75 cm. So the racket is twice as long as the hand, so the linear speed of the racket face is twice that of the hand. If the hand speed of a male athlete is 170km/h, then the speed of the racket head is 340km, and the starting speed of badminton is about 680 km/h. In fact, the speed record of badminton in Fu Haifeng is 332km/h, which is about 1 times worse. So the previous data should be a coincidence.
So how to understand this gap? What does this gap mean? How to improve?
First of all, badminton is against killing the ball, so the ball must have a certain speed. According to the formula (R- 1), this speed will cancel out an amount with the same speed. For example, when killing the ball, the speed of coming the ball is 20 km/h, then the speed of going the ball will be reduced by 20 km/h, so the speed of killing the ball is related to the situation at that time. If the opponent passively picks the backcourt, the speed of the cross will be slow, if not, the speed will be faster, and the effect of ball speed offset will be much more obvious.
Secondly, the most critical reason is that the process of badminton hitting the ball is not a complete elastic collision, but an incomplete elastic collision process of energy conversion. The reason why we use the model of complete elastic collision to analyze is to simplify complex problems, because there is no data to provide the elastic coefficient of this process! We should assume that it is an elastic collision, and then analyze the elastic loss in this process from other aspects. In the process of hitting the ball, badminton, racket face and racket will be deformed, and some kinetic energy will be converted into elastic potential energy and consumed! The greater the deformation, the greater the energy consumption. Let's look at the deformation in this process and how to overcome it as much as possible.
First of all, the deformation of badminton is very intense. Although the photos of this moment have not been seen or found, we know that badminton can be deformed without much effort. When killing the ball, the force is much greater, and the deformation is naturally not small.
Secondly, the racket face is deformed. The deformation of the racket face is related to the pounds of the racket. The higher the number of pounds, the tighter the racket face and the smaller the deformation.
And deformation of the intermediate rod. The hardness of the middle bar has a direct influence on the deformation of the middle bar, and the harder it is, the smaller the deformation is.
As for the energy consumption caused by these deformations and their influence on the speed, we have to give a qualitative analysis in view of the lack of experimental conditions.
But with these analyses, we can choose the racket according to our own characteristics. In order to kill the ball faster, the hardness and pounds of the racket are often higher and higher.
Let's take a look at a theoretical origin of the highest point hitting. When I first played ball, the coach always emphasized a concept? The concept of hitting the ball at the highest point confuses many people and thinks it is a mysterious skill. In fact, from the previous analysis, we know that the origin of hitting the ball at the highest point is that the linear speed is related to the radius of rotation. The longer the stretching, the larger the radius of rotation and the faster the linear speed. We usually feel this way when we play ball. It is true that holding the ball at the back end of the racket handle is more labor-saving than holding the ball at the front end, and this is only about 4~5CM. 4~5 cm is equivalent to about 4% of hand length+beat length = 140 cm, and people can obviously feel the change of 4%. This highest point refers to your own highest point. For example, if you are1.75m, then your highest point is different from that of a person with1.85m..
Now that we have reached the highest point, let's say it again. There are two reasons for hitting the ball at the highest point besides the large radius of rotation. One is that the process of joint locking is faster, so that muscle strength can be transmitted through joints in a shorter time, and the strength loss is small; The other is that the angle is sharper when killing the ball, that is, sharper. Therefore, the height and arm length have a great influence on badminton. Being tall and having long arms generally means that people with long arms have two natural advantages: the highest point is high, the ball is sharp, the higher the linear speed, the faster the ball is, and the so-called sharp and fast account for a lot? Cheap? . Of course, confrontation is not standing, but moving. In this respect, tall people are not dominant. Therefore, the height of badminton players should not be too short or too high.
Badminton 76 speed 77 speed difference:
The flying speed of badminton is directly related to the weight of the ball. The heavier the ball, the faster the ball speed. The flying speed of badminton is generally indirectly expressed by the weight of the ball. Regular badminton manufacturers have their own set of standards for badminton speed (weight), which are generally marked on the top cover of the ball tube.
According to the rules of the World Badminton Federation badminton competition, the weight of badminton is 4.74 grams to 5.50 grams ... In the past, the corresponding weight was often used to express the ball speed. For example, balls weighing 4.9 grams and 5.0 grams will be labeled 49 and 50 respectively. There are also European units of weight expressed in grains, such as 77 grains (green) and 78 grains (green). At present, the YONEX brand commonly used in international competitions is often marked with simple numbers from 0 to 5. The smaller the label, the lighter the ball and the slower the ball speed. On the contrary, the heavier the ball, the faster the speed. At present, the international standard is marked with green, and 76 77 78 79 units on the barrel are all green, which is the most widely used. The smaller the value, the lighter the weight.
Some manufacturers will provide the appropriate temperature comparison of this model (speed) on the bulb: (The following temperature VS speed is only based on standard altitude and humidity, and relevant parameters need to be measured and adjusted in non-standard altitude and humidity areas! Of course, these all refer to the applicable temperatures at the same altitude, and regions at different altitudes cannot choose balls according to this comparison.
76 green (4.9 grams) suitable temperature 27-33 degrees; The suitable temperature of 77 (5.0g) green is 20-27 degrees; The suitable temperature of 78 green (5. 1 g) is 14-20 degrees; The suitable green temperature is 7- 14℃;
YONEX's No.0 ball indicates that the suitable temperature is above 33℃; 1 ball 27-33℃; The second ball is 20-27℃, the third ball is 14-20℃ and the fourth ball is 7- 14℃.
In China, the ball speeds are mostly 76 and 77 greens, 77 greens below 30℃ and 76 greens above 30℃.
The speed of badminton is not only related to its own weight and speed, but also affected by temperature, humidity, altitude and other factors. Generally speaking, the higher the altitude, the higher the temperature and humidity, and the lighter the weight of the ball. Because the higher the altitude, the higher the temperature, the smaller the air density, the smaller the air resistance when badminton flies, and the faster the ball will be. It's time to use a lighter (slower) ball. Under such circumstances, it is necessary to choose a lighter ball. On the other hand, the lower the altitude, the lower the temperature, the greater the air density and air resistance, and the slower the speed of the ball. Therefore, badminton used in low altitude and low temperature areas is heavier. When the air humidity is high, the water content of feathers will also increase, which will lead to the increase of the weight of the ball and the speed of the ball. So the higher the humidity, the lighter the ball used. According to referee Lei Mingji, last year's World Youth Championship held in Guadalajara, Mexico, used the YONEX ball of 1 that he had seen for the first time in his life. Because the altitude there is as high as 1800 meters, the air is thin and the air resistance is small, so the ball chosen is relatively light.