In the training practice of shot put, it is generally found that the principle of mechanics based on the projectile motion in physics has great limitation and inaccuracy in the practical application. This not only caused people to put the shot mechanics of the foundation in doubt, but it also made some people to begin to deny the mechanics of the foundation. In fact, the shot-put movement is the projectile point higher than the falling point of the projectile movement of the fact is objective, is undeniable. The crux of the problem is that people who are involved in the process of application look only from the perspective of physical exercise awareness and make an analysis of the characteristics of the shot put movement, without applying the conditions of the sports mechanics principle itself. Therefore, in the projectile motion, based on the principle of mechanics of physics, there are many limitations in practical application and accuracy. Through the mathematical analysis of the principle of mechanics of shot put, this paper aims to explore the reasons for the inaccuracy of the principle of mechanics of shot put in practice and provide a reference for further improvement of the same [1].
When we study the shot put movement, we can separate the movement process before and after shooting, and only in this way can we understand the characteristics and rules of the shot put movement. But it's important to note that this separation must be conditional, and that's the premise of any process.
From a set of outstanding women far mobilisation in China from a group of outstanding women's shot put data of the athletes in China (Table 1), by establishing a mathematical correlation analysis model [2], seeking and shoot height, Angle velocity v T h three factors of the effect of throwing distance s size, in training and competition for athletes and coaches have certain theoretical guiding significance.
Shot put data of an elite athlete in China
13.51 | 28.69 | 2.00 | 20.30 |
14.08 | 35.13 | 1.95 | 21.76 |
13.82 | 30.80 | 2.1 | 20.49 |
13.40 | 36.02 | 2.11 | 20.24 |
13.77 | 34.64 | 2.01 | 20.84 |
13.41 | 38.74 | 1.92 | 20.02 |
13.56 | 35.33 | 1.77 | 20.10 |
14.08 | 34.60 | 1.89 | 21.58 |
13.23 | 39.13 | 2.10 | 19.84 |
13.35 | 34.08 | 1.89 | 19.26 |
13.07 | 39.68 | 1.97 | 19.17 |
13.39 | 34.14 | 1.83 | 19.62 |
13.30 | 37.74 | 1.76 | 19.76 |
13.58 | 37.75 | 2.02 | 20.76 |
13.48 | 40.56 | 2.00 | 20.33 |
13.39 | 34.67 | 2.01 | 19.85 |
13.35 | 39.27 | 1.91 | 19.81 |
13.37 | 36.98 | 1.95 | 19.62 |
13.46 | 38.68 | 1.83 | 19.59 |
13.20 | 42.48 | 1.98 | 19.58 |
13.18 | 38.62 | 1.89 | 19.36 |
13.21 | 41.32 | 2.03 | 19.82 |
13.38 | 36.10 | 1.94 | 19.71 |
The throwing distance of the ball depends on the speed, Angle and height of the ball when it is thrown. Among them, the initial speed has the biggest impact on the throwing distance. For professional athletes after hard training, the shooting speed of the ball can be stable at a higher level, and the shot put speed is generally 11.0–15.0 m/s because it cannot be increased at will. The shooting height is also relative to a certain amount. Therefore, to find the best shot Angle, it imperative to improve the shot putting technology to get the longest distance. Next, we build a mathematical model of the problem.
Shot put before and after the movement from the surface form is relatively independent. The movement before the hand is a biological movement based on the characteristics and laws of human body movement, while the movement after the hand is a projectile movement. But because the shot speed, shot Angle and shot height from the shot before the movement process, and shot before and after the shot is a continuous uninterrupted process, the shot before the movement is the basis and condition of the shot after the shot after the movement is the continuation of the shot before the movement and effect. In this sense, the shooting movement after the shot put is not a simple shooting movement, but it is a shooting movement that includes the law of biological movement. Although these two movement processes have their own relatively independent movement rules, the basic conditions, continuity and effect between the movement before and after the shot put shooting determine that the movement before and after the shot put shooting is closely linked, restricted and influenced by each other [3]. This shows that there is a significant causal relationship between the two movement processes before and after shot putting.
According to the data sequence of shot put score, shooting speed, shooting Angle and shooting height in Table 1, as the behavior data sequence, let's call each of them
Model building and solution Suppose the initial velocity of the shot put shooting is T, the shooting height is h, the Angle between the initial velocity T and the ground is a, the flight trajectory of the ball is shown in Table 2, then the flight time of the ball from the shooting point A to the highest point B is taken
The theoretical basis of the optimal shooting Angle is based on the projectile motion which is higher than the landing point in physics. It is based on the movement index (shooting speed T, shooting Angle V, shooting height H) and the movement effect (shooting point and landing point projection J in the horizontal plane) function relationship, through mathematical operations.
Formula (1) is the function relation between the shooting speed V, the shooting Angle T, the shooting height h and the projection J of the shooting point and the landing place on the horizontal plane
According to the differential function relation, the derivative of function formula (12) is made equal to 0. Through calculation, the function relation (14) between the optimal shooting Angle T, the shooting speed V and the shooting height H is obtained.
Shot speed V, shot Angle T, shot height H are the three instantaneous movement indicators of shot put shot. But these three indexes are not suddenly obtained at the moment of the shot, but through the unified movement process of the shot and the human body before the shot. In the movement process of the shot and the human body, through the movement process of the human body, the speed of the shot from 0 to the instantaneous speed when the shot is shot; The height of the hand is also from a certain height (lower than the height of the hand) to the height of the hand; The hand Angle is the movement effect of the joint coordination of the human body. This shows that the shooting speed V0, the shooting Angle
When the height of the hand is 2 m, the calculation results in Figure 1 can be obtained. In the figure, T represents the Angle, Y represents the angular module, and Z represents the descent Angle. R stands for the corner of the ground. The simulation results show that the optimal shooting Angle T and landing Angle R are complementary angles to each other. This result is in good agreement with the conclusion from the literature that when the shot is shot at the best Angle of release, the velocity vector of release and velocity vector of landing are perpendicular to each other.
Like the best shot Angle, the best shot Angle varies with the speed of shot put. When the speed is small, the optimal landing Angle is close to 90°, which means that 90° is the asymptotic Angle of the optimal landing Angle at a small speed (it can be an Angle that is infinitely close but never reached). As the velocity exceeds 14 m/s and increases, the Angle of impact decreases gradually, as it approaches at 45°, which is another asymptotic Angle at the maximum velocity.
When the speed becomes very small, since the optimal hand Angle tends to 0°, and the deflection Angle of the hand is equal to 45° minus the optimal Angle of the hand, it gradually approaches 45°, that is to say, 45° is the asymptotic Angle of the deflection Angle of the hand at a small speed.
When the speed increases gradually, the optimal Angle of release gradually tends to 45°, so the deflection Angle of release gradually tends to 0°, which is the asymptotic Angle of release Angle under the maximum speed.
The initial speed V is the most important factor affecting the throwing distance. If the initial speed increases by 1 m/s, the throwing distance will be increased by 2–3 m. Therefore, athletes should do everything possible to improve the throwing technique, strengthen strength training, and try to improve the initial throwing speed. Under the condition of constant initial velocity, the throwing distance increases with the height of the shot. For every 5 cm increase in the height of the hand, the throwing distance will increase by about 4.5 cm. Therefore, when selecting materials, athletes should pay attention to both strength and height. In the case of similar strength, tall people should be chosen first.
There is an important relationship between throwing Angle and throwing distance. The throwing distance in the table is the maximum distance achieved under the optimal throwing Angle. Take the throwing height of 1.90 m and the throwing speed of 14.5 m/s for example, the optimal throwing Angle of 42° 40′ is 4240′, and the corresponding distance is 23.28 m, if the ball is thrown from either 4140′ or 43 40′, the throwing distance will not be >23.26 m. The difference of 2 cm is extremely precious for high-level athletes, which often determines whether they can win the championship in major competitions. The only reason is the difference of 1° of ball shooting Angle, so it can be seen the importance of serious training and strengthening skills [7]. For a certain height of the ball, the Angle of the ball will increase with the increase of the initial velocity. For professional players, the Angle of the ball should be between 41° and 43°
Table 1 can provide reference for athletes to find personal gap and improve throwing technique. Shot put height can be easily measured by taking the average height of a number of effective throws. Shot put speed can be measured by the velocimeter, or by the following methods. It can be obtained from Eqs. (3), (7), (8) and (9)
There is an optimal shot Angle, and it can be calculated mathematically. But the precondition is to first determine the changing relationship between the Angle of the hand and the speed of the hand, the height of the hand (the speed of the hand has little influence on the height of the hand, if ignored, can only determine the changing relationship between the Angle of the hand and the speed of the hand). In this way, we can use the method of conditional extremum problem to calculate the best shooting Angle. When the functional relation (11) is applied to study the influence of shooting Angle and shooting speed on the shot put distance, the effect of index change on the shot put distance should be considered first [8]. When the shot putting Angle reaches a certain value, every increase of 10 will have little effect on the shot putting distance, and the effect will be smaller and smaller with the increase of shot putting Angle.
The contribution of shooting speed V to S is much greater than that of T and H, so we must strengthen this aspect of training in training and competition, that is, we must strengthen the training of arm strength, especially the explosive power, to maximise the speed of shooting. Release speed and release Angle restrict each other, there is an obvious dependence relationship. Therefore, when improving the speed of shooting, the shooting Angle should be considered comprehensively to adjust to the ideal state of the athletes. The height of the hand influences the throwing distance, which can be controlled by selecting the athletes with the height advantage, which is a difficult factor to control in the throwing process [9, 10].
Through the process of building a model from simple to complex, the mathematical principle of shot putting is revealed. However, there are still many problems to be solved, among which the height problem is complex. At the current level, it is not possible to find a reasonable height, because it involves many factors. The movement of the shot can be decomposed into the implicated movement of the human body centre of mass and the relative movement of the human body centre of mass. The motion of the shot meets the law of progressive speed, progressive energy and abrupt energy and the transmission law of moment of momentum. In the process of pushing the ball, the principle of maximum work, maximum impulse and maximum moment of momentum must be followed. However, the development of mathematical correlation will provide a useful attempt to establish a reasonable and scientific model. To improve and perfect the shot put sports technology, we should not only take the physical movement characteristics of the shot as the basis but also consider the characteristics of the biological movement process before the shot is shot. It is more meaningful to give full play to the maximum biomechanical effect of the human body to get good results.