Introducing a series of workouts for practicing a strike with the inside of a lift. The training process is built in such a way as to sequentially complicate the conditions for the implementation of this technical element. Watch the video “Kicks on the ball in football”, memorize equipment and train in practice.
Practice hitting a stationary ball
The first and simplest exercise is a shot on goal with the ball static. First, a series of punches to the right corner of the goal. It should last, until the percentage of hits exceeds 50%. After you can start striking in the left corner. The final part of this exercise is the alternation of strokes in different angles.
The footballer independently learns to adjust his movement, depending on the task. Changing the position of the supporting leg and touch point on the ball. The most important thing in this process is the repeated execution of exercises. To bring the strike technique to automaticity, you need to beat, beat and beat. Training allows you to hone an accurate and powerful blow.
Getting to the execution of the standard position. Having placed the ball near the front line, a canopy is carried out to the far post. The teammate must close it. During the successful completion of such an exercise, a high emotional background is ensured. We carry out similar canopies on both sides. To complicate the use of training racks. Putting them on the near post, imitate a group of defenders.
We return to practicing striking on goal. We mark the trajectory for takeoff with chips. Thereby changing the angle at which the footballer approaches the ball. The player will need to constantly change the backswing. By practicing different accesses to the ball, the player gains practice.
With football chips, mark the line a meter from the 11 meter point. Making a kind of ruler. The trainee must strike, farther and farther from the goal. Increasing strength and practicing every hit in height.
For the next exercise, you need to place 3 balls 5 meters from each other. Punching into the goal frame is necessary without stopping. Having shot with one ball, immediately move to the next and strike already at it. By setting a time frame between strokes, you can complicate the task.
We simulate the wagering in the wall and a shot on goal. We place the first ball on the penalty line. Away from the ball, at a farther distance from the goal, put a chip. About 5 meters from the ball. And one more at 10 meters. Taking the second ball, we move the same 5 meters from the second chip. We circle the second chip and give an imaginary pass to the first. Having immediately taken a run, the shot is delivered on goal with the first ball. We make the exercise more realistic by adding a defender. He, in turn, tries to grab the batter with his hand.
Running between training poles, the player must pass to the partner. A partner stands in the chip-marked area. But you need to complete the transfer only at his signal by hand. This training is intended to develop a better vision for a partner. And also teach you how to move with your head up.
Practice hitting the ball in motion
Kick on a rolling ball. After passing the pass to the partner, you will receive a return pass under attack. It happens that there is no partner. Or his ability to give an accurate pass to the touch, wants to leave the best. Then without a portable wall can not do.
There are many options for complicating this technique. Do this challenge for a couple of players in the form of competition. Thus, it will be more difficult for the striker, because the result factor puts pressure on him. And putting the wall at an angle, the return pass will be on top.
Exercises more similar to real situations on the football field.
Reception of the ball after an inaccurate removal, followed by a shot. The ball should fly high and within a radius of 5 meters from the player performing this technical element. Winding passive (no more than 2 movements) protector, with a further blow. In this case, the batter should also not have excessive touches on the ball. Before throwing the ball through the defender - no more than 3. After that, one more is allowed for a convenient part-time job under the blow. Acceptance and blow after a lumbago or canopy from the flank. You need to do this in two touches. Take and punch.
Kicking the ball in football is one of the most important components of this game. Train, hone your skills and score beautiful goals.
In game sports it is often necessary to observe how the ball moves in the air along a strongly curved path, causing surprise not only among the players, but also among the spectators. French scientists conducted a series of experiments to study the movement of rotating balls in water and based on the data obtained, built a theoretical model of their behavior. Using the developed model, scientists answered the question in which sports the flight of the ball can occur in a steep arc.
Increasingly, various phenomena from the field of sports are becoming the subject of research by physicists. The most attractive from a scientific point of view, sports with a ball. The fact is that, due to air resistance, the movement of the ball turns out to be a generally non-linear process, and therefore, despite the apparent routine, it is of great interest for theoretical and experimental study.
Non-linearity of the ball’s behavior can be observed, for example, during broadcasts of football matches, when commentators reward the trajectory of its flight with epithets such as “fantastic”, “incredible”, “crazy”, etc. One of the most striking and famous examples of such an “incredible” trajectory - free kick by Brazilian footballer Roberto Carlos (see video), which he struck June 3, 1997 at the gates of the French team. When watching the video, at first it may seem to the viewer that the ball flies far to the right of the goal, but then the direction of its path is sharply curved, and to the amazement of the goalkeeper of France, it flies into the right corner of the goal. The influence of the wind is absolutely excluded, because at that moment there was calm weather.
So it is not surprising that this flight of the ball has become the subject of a comprehensive study of scientists (see, for example, the article “Physics of Football” in the journal “Technique of Youth”). At a qualitative level, the cause of the ball moving in a steep arc is known - this is the force arising from the rotation of the ball, which is often called the Magnus force. But, despite repeated attempts, no adequate theoretical model was created that could correctly quantitatively interpret the flight of the ball.
This omission was recently corrected by a group of French scientists. In his article The spinning ball spiral, published in the journal New journal of physics, they not only quantitatively modeled the goal of Roberto Carlos, but also showed in which sports the ball movement can have the same “fantastic” trajectory.
To begin with, the authors of the article, after conducting a series of experiments, studied the trajectories of rotating polypropylene and polyformaldehyde balls with radii of several millimeters, which were shot into an aqueous medium using a special slingshot. The design of the slingshot made it possible to give the balls controlled values \u200b\u200bof rotation and speed, as well as the specific angle at which they were supposed to fall into the liquid. The choice of water and polypropylene or polyformaldehyde is due to the fact that the densities of these substances are very close to each other. Therefore, it is possible to simplify the task and not take into account the effect of gravity on the parameters of the motion of the balls. The trajectory of the studied objects was detected by a high-speed video camera.
A visualization of one of the experiments can be seen in Fig. 1. It shows a series of still pictures showing the position of a rotating polypropylene ball in water.
It can be seen with the naked eye that the ball moves in a spiral, and note that in the first four photographs its path is similar to the flight of the ball launched by Roberto Carlos.
Thus, the experiment gave the already obvious conclusion that the cause of the curved motion of the ball is its rotation. Now it was up to the construction of an accurate theoretical model of the dynamics of balls in water.
In the process of movement, two forces act on the object under study: the drag force, which under these conditions is proportional to the square of the ball’s speed, and the Magnus force, proportional to the product of the ball’s speed and the angular velocity of its rotation. To take them into account, you need to know exactly the value of the proportionality coefficients included in the formulas for both forces. Their values \u200b\u200bdepend on the geometry of the body, as well as on how much the body perturbes the environment with its movement. This disturbance in hydro- and aerodynamics is characterized by a dimensionless quantity - the Reynolds number. The higher the Reynolds number, the stronger the perturbed medium under the action of a moving body. For given intervals of Reynolds number, there is a proportionality coefficient in the formulas for the forces. Fortunately, for spherical bodies, the values \u200b\u200bof these coefficients, depending on the value of the Reynolds number, were measured; therefore, the authors used already prepared experimental data.
Another difficulty that scientists successfully overcame was purely mathematical in nature. If you try to write down the equations of motion (Newton’s second law) in the traditional Cartesian coordinate system, they will not have an analytical solution because of their appearance. Of course, you can use the existing programs for numerical calculation, but then the “visualization” in understanding the ongoing process is lost, more precisely, how the parameters of the ball (rotation speed, radius, density) and the medium will affect the trajectory of movement. Since the experiments clearly demonstrated the spiral path of the sphere, the authors used the equations of motion written in a special curvilinear coordinate system, sometimes called the Frenet-Serre coordinate system.
Thanks to this mathematical “trick”, the equations allow an analytical solution, and accordingly, it is not necessary to resort to any numerical calculation. Further, using the well-known relations between the Frenet-Serre coordinate system and the Cartesian coordinate system, the authors of the article constructed graphs of solutions of the equations of motion, which, in essence, determine the trajectory of a rotating ball in water (Fig. 2). As can be seen from fig. 2, the movement of the spinning ball passes in a spiral. The red spiral corresponds to the case when the speed of rotation of the polypropylene (polyformaldehyde) ball during movement remains constant. Obviously, such a picture has little in common with reality. If we now take into account the fact of a decrease in the angular velocity of rotation (realistic situation), then the path of the object under study will follow a blue spiral, which, as can be seen, is in excellent agreement with experimental data.
Ultimately, as shown by the analysis of the expression describing the trajectory of the ball, its path becomes straightforward. The distance at which the curvature of the ball traverses is approximately equal to the value designated by the authors as (this is also seen from the graph in Fig. 2). This parameter, which the authors also called the “characteristic scale of the spiral,” is determined through the radius of the ball, the ratio of the densities of the substance of the ball and the medium, and the proportionality coefficient included in the formula for drag. - A very important parameter, we will talk about it below.
So, the authors of the article created an adequate quantitative theory of the motion of a rotating ball in water, which is in excellent agreement with experiment. However, since at the very beginning of this note we were talking about the flight of the ball, the question arises as to the applicability of the model described here under conditions when the influence of gravity cannot be neglected, and the aqueous medium changes to air. How much gravity can distort the spiral path of a ball rotating in the air?
To answer these questions, the authors provide a table in which they collected the main parameters of sports games with the ball. Using the given values, the authors calculated the characteristic scale of the spiral along which the ball would move in the absence of gravity (the same thing), and the characteristic distance (scale) of gravity U 0 2 / g, after which the ball's trajectory is determined mainly by gravity.
A comparison of the last two columns of the table makes it possible to determine in which sports aerodynamics dominate (which is precisely reflected in the spiral path of a rotating ball), and in which gravity. It can be seen that in table tennis, golf and tennis, the scale of gravity is several times smaller - therefore, in these sports, the spinning ball will move in a spiral. The opposite picture takes place in basketball and handball: gravity dominates here, which means that the movement of a rotating ball does not lead to a serious curvature of the trajectory. Finally, there is a category of sports in which the effects of aerodynamics and gravity are approximately the same - football, baseball and volleyball.
In this list, football deserves special attention. For him, the characteristic scale of the spiral (\u003d 54 m) is half the characteristic scale of gravity. This means that the movement of a rotating ball will deviate significantly from a straight line only when it has flown a sufficiently large distance. Only in this case the trajectory of the ball becomes "incredible."
Returning to the goal of Roberto Carlos, we note that the distance to the goal of the French team during the execution of a free kick by the Brazilian national team player was approximately 35 meters. This value, although close to the characteristic scale of the spiral in football, is still less than it. However, since Roberto Carlos not only gave the ball a spin, but also due to bounce he told him that the speed was 1.5 times higher than the “usual” maximum value of 30 m / s indicated in the table, the scale of gravity more than doubled, and gravity began to have a much smaller effect on the flight of the ball. This, combined with a large distance to the goal, led to the ball flying into the goal in a steep arc.
The Magnus effect is used in the construction of wind generators, it can also be observed in chemistry, in the separation of substances. The Magnus effect is also observed in game sports with the ball: tennis, volleyball, football, in particular with “twisted” blows of the “dry sheet” type.
SECTION 2
PROGRAM OVERVIEW SOCCERNASA
The equations of motion are complicated taking into account the strength of Magnus. In addition, the introduction of non-linear terms in the equation, such as air resistance, makes the analytical study of the equations extremely difficult. In such cases, they usually resort to a numerical solution of the resulting equations and use specially developed software for this. To calculate the trajectories of complex objects, visualize flowing flows and select the optimal geometric and speed characteristics, a universal software package is successfully used COMSOL,. For example, the flight of a “twisted” soccer ball was studied and turbulent air flows during the flight were observed, see Fig. 2.1. Note that the article owes its appearance to the famous blow of the Brazilian Roberto Carlos in the match France - Brazil in 1997. Programs are also popular. SIGMAFLOW and ANSYS FLUENT production of Russian specialists.
All these programs require the user to have deep knowledge of higher mathematics, as well as knowledge of aerodynamics at a professional level.
Currently, computer games dedicated to football and various football simulations are also very common. The main feature of such programs is the combination game of football with the opposing team and the creation of the “presence effect” on the football field. In this case, insufficient attention is paid to the physical aspects of hitting the ball and the trajectory of the ball, however, it should be noted that the developers do not set such a goal.
Glenn Specialists NASA Research Center has developed SoccerNASA. According to the developers, this program is specifically designed to familiarize students with the dynamics of the movement of a soccer ball, taking into account aerodynamic forces. There is a similar program for baseball, basketball, etc.
The operation of the SoccerNASA program is based on the integration of equations of motion (Newton’s second law), taking into account various factors that are introduced into the equations in the form of coefficients and additional terms. This program was used by us for numerical calculations. Note also that SoccerNASA is in the public domain.
Consider the interface of SoccerNASA. It consists of a single window without tabs. The left part contains the NASA logo, an image of a soccer ball for which the inclination of the axis of rotation is shown (controlled by the parameter Spin Axis), as well as an indicator of a goal. Below is a screen for visualizing the flight of the ball. The program provides several viewing angles.
MINISTRY OF EDUCATION AND SCIENCE OF THE DONETSK PEOPLE'S REPUBLIC
GPOU "DONETSK PROFESSIONAL LYCEUM OF MOTOR TRANSPORT"
“DRY SHEET”. MODELING FOOTBALL BALL FLIGHT
Work completed:
Vardyak Vera Andreevna,
student of group No. 105
GPOU "DPLA"
Scientific adviser:
Kinash Irina Mikhailovna, a teacher of physics of the highest category GPOU "DPLA" in Donetsk
Donetsk - 2017
“DRY SHEET”. MODELING FOOTBALL BALL FLIGHT.
Vardyak Vera Andreevnva
student of the group №105 GPOU "DPLA"
scientific adviser : Kinash Irina Mikhailovna, a teacher of physics of the highest category GPOU "DPLA" in Donetsk.
The work is devoted to the numerical simulation of the flight of a rotating spherical body in the air, which brings the ball trajectory closer to the “dry sheet” impact. SoccerNASA was used as the modeling environment, which does not require aerodynamic knowledge from the user and, at the same time, gives physically meaningful results. As a result of the simulation, some limit parameters were found that allow the ball to hit the target.
The results and conclusions of the work can serve as recommendations for beginner football players.
CONTENT
INTRODUCTION ………………………………………………………………………………… .4
SECTION 1. Qualitative explanation of the flight of the “swirling” ball based on the Magnus effect ……………………………………… ..6
SECTION 2. Overview of SoccerNASA …………………………………… ..... 9
SECTION 3. Simulation of ball flight and results ………………. ……… ... 13
CONCLUSIONS .............................. ...................... 17
REFERENCES .............. ..............................................
INTRODUCTION
Putting the ball into the field from the corner mark is a fairly common standard action in modern football. Up to twenty or more corner kicks can be played per game. The FIFA rules allow a direct shot during a corner kick: “A goal scored directly from a corner kick counts, but only if it is scored into the goal of the opposing team," p. 52. The ball trajectory is so twisted that the players and the defending goalkeeper the teams literally “follow their eyes” the ball flying into the target. This rare and spectacular blow got its own name - “dry leaf”. It is believed that for the first time “dry leaf” was applied by Valery Lobanovsky. Subsequently, such “cut” goals scored by Roberto Baggio, Andrea Pirlo, Roberto Carlos, David Beckham and others.
Roberto Baggio (born 1967). Italian soccer player. He played for clubs:Vicenza, Fiorentina, Juventus (Turin), Milan, Bologna, Inter (Milan), Brescia. The author of the “dry sheet” at the gate of Lecce, 2001Blow “dry sheet” is interesting not only from the point of view of football aesthetics, but also from a physical point of view. On the one hand, the study of the “twisted” ball may be a continuation of the school theme “motion of a body thrown at an angle to the horizon”, on the other hand, a deeper study of the issue leads to such complex concepts as turbulent flows and unsteady gas motion. At the same time, the “dry sheet” itself can be repeated in the yard or on the school site.
ALL PHOTOS
In order for a soccer ball to fly a greater distance and with a higher speed, it must be directed at an angle of 25-30 degrees from the surface of the earth, although this contradicts the laws of physics. This conclusion was made by the scientists of the British University of Brunel University Nicholas Lintorn and David Everett, who devoted a special study to the solution of this phenomenon, writes the publication Nature (the full text on the website Inopressa.ru).
The experts only confirmed what many football players already know in practice: when you need to make a blow as far and as strong as possible, mathematical principles are not always applicable. However, Lintorn and Everett are ready to give some advice to football coaches on how best to execute a long shot.
Every physics student knows: in order to get the maximum range of a shot when firing from an artillery gun, the barrel inclination should be 45 degrees from the ground. But football players, like golfers, javelin throwers, and discus throwers, usually use a trajectory that has an angle much smaller - 30-35 degrees. Players have developed such a trajectory as a result of long practice.
“We cannot explain why the effective trajectory is so unusual,” says Lintorn. He and Everett explored the football canopy, examining the video footage of football players performing this kick under various trajectories. Then they tried to describe the obtained data on the speed of the ball, the distance over which it flew, and the time of its flight, in the form of mathematical equations.
This gave researchers the opportunity to find the most optimal angle at which to direct the ball so that it flies the greatest distance. It turns out that it should be from 20 to 35 degrees. Information on the results of the study was published in the journal Sports Biomechanics2.
Why are there so great differences from traditional mechanics? According to Lintorn, the fact is that traditional mechanics do not take into account the structural features of bones and muscle structure. human body, and they allow you to apply more power to the ball, which flies at a lower angle than at a higher. Therefore, a ball flying at a lower angle has a higher speed. And speed is the main factor determining the flight range.
Sometimes it is not the range of the impact that matters, but the flight time of the ball. For example, when you need a quick pass to catch the enemy by surprise. Scientists have found that in this case the trajectory should be several degrees lower. This will hardly change the range, but it can change the flight time, and the saved tenths of a second sometimes become crucial during the match.
“Hinged kicks are widely practiced in football,” says Lintorn. “Most football teams have a player who specializes in such kicks.” Knowing how the craftsmen carry out these awnings can help coaches understand that they should not apply certain rules of physics to achieve optimal results.
Perhaps the greatest value from this study will be derived by school teachers - with its help it is easy to increase children's interest in physics. After all, everything related to sports arouses great interest among students, said Lintorn.