An impact can be considered instantaneous if its duration. The phenomenon of shock. Point offset on impact

The mechanism of impact.   In the mechanics of an absolutely hard-solid body, a shock is considered as an abrupt process, the duration of which is infinitely small. During an impact, large but instantly acting forces arise at the point of contact of the colliding bodies, leading to a final change in the momentum. In real systems, finite forces always act during a finite time interval, and the collision of two moving bodies is associated with their deformation near the point of contact and the propagation of the compression wave inside these bodies. The duration of the impact depends on many physical factors: the elastic characteristics of the materials of the colliding bodies, their shape and size, relative velocity of approach, etc.

The change in acceleration in time is usually called the pulse of shock acceleration or shock pulse, and the law of change in acceleration in time is called the shape of the shock pulse. The main parameters of a shock pulse include peak shock acceleration (overload), duration of shock acceleration, and pulse shape.

There are three main types of reaction of products to shock loads:

* ballistic (quasi-amortization) mode of excitation (the period of natural vibrations of the EU is longer than the duration of the excitation pulse);

* quasi-resonance excitation mode (the period of natural vibrations of an EU is approximately equal to the duration of the excitation pulse);

* static mode of excitation (the period of natural vibrations of the EU is less than the duration of the excitation pulse).

In ballistic mode, the maximum value of the acceleration of the EU is always less than the peak acceleration of the impact shock. Quasi-resonant quasi-resonant excitation mode is the most rigid rigid in magnitude of excited accelerations (m more than 1). Under the static excitation mode, the response of the EC completely repeats the acting pulse (m \u003d 1), the test results do not depend on the shape and duration of the pulse. Static tests are equivalent to linear acceleration tests, as it can be seen as a blow of infinite duration.

Impact tests are carried out in a quasi-resonant excitation mode. Impact strength is assessed by the integrity of the EU design (absence of cracks, chips).

Impact resistance tests are carried out after impact tests under electrical load to test the ability of the EA to perform its functions under mechanical shock.

In addition to mechanical shock stands, electrodynamic and pneumatic shock stands are used. In electrodynamic stands, a current pulse is passed through the excitation coil of the mobile system, the amplitude and duration of which determine the parameters of the shock pulse. On pneumatic stands, shock acceleration is obtained when a table collides with a projectile fired from an air gun.

The characteristics of shock stands vary within wide limits: load capacity, load capacity - from 1 to 500 kg, number of beats per minute (adjustable) - from 5 to 120, maximum acceleration - from 200 to 6000 g, duration of strokes - from 0.4 to 40 ms.

In mechanics, shock refers to the mechanical effect of material bodies, leading to a finite change in the velocities of their points over an infinitely small period of time. Impact motion is the movement resulting from a single interaction of a body (medium) with the system under consideration, provided that the smallest period of natural vibrations of the system or its time constant is comparable or longer than the interaction time.

During impact interaction, shock accelerations, velocity or displacement are determined at the points under consideration. Together, these effects and reactions are called shock processes. Mechanical shocks can be single, multiple and complex. Single and multiple impact processes can affect the apparatus in the longitudinal, transverse and any intermediate directions. Complex shock loads affect an object in two or three mutually perpendicular planes simultaneously. Shock loads on aircraft can be both non-periodic and periodic. The occurrence of shock loads is associated with a sharp change in the acceleration, speed or direction of movement of the aircraft. Most often, in real conditions, a complex single shock process occurs, which is a combination of a simple shock pulse with superimposed oscillations.

The main characteristics of the shock process:

• the laws of change in time of shock acceleration a (t), velocity V (t) and displacement X (t) \\ duration of shock acceleration m is the time interval from the moment of appearance to the moment of disappearance of shock acceleration, satisfying the condition a\u003e an, where an peak shock acceleration;
• the duration of the shock acceleration front Tf is the time interval from the moment the shock acceleration appears to the moment corresponding to its peak value;
• the coefficient of superimposed oscillations of shock acceleration is the ratio of the total sum of the absolute values \u200b\u200bof the increments between adjacent and extreme values \u200b\u200bof shock acceleration to its doubled peak value;
• shock acceleration momentum is the integral of shock acceleration over a time equal to the duration of its action.

According to the shape of the curve of the functional dependence of motion parameters, shock processes are divided into simple and complex. Simple processes do not contain high-frequency components, and their characteristics are approximated by simple analytical functions. The name of the function is determined by the shape of the curve approximating the dependence of acceleration on time (semi-sinusoidal, cosanusoidal, rectangular, triangular, sawtooth, trapezoidal, etc.).

A mechanical shock is characterized by a rapid release of energy, resulting in local elastic or plastic deformations, excitation of stress waves and other effects, sometimes leading to disruption of the functioning and destruction of the aircraft structure. The shock load applied to the aircraft excites rapidly damped natural oscillations in it. The value of the overload upon impact, the nature and speed of the stress distribution along the aircraft structure are determined by the strength and duration of the impact, and the nature of the change in acceleration. Impact, acting on the aircraft, can cause its mechanical destruction. Depending on the duration, complexity of the shock process and its maximum acceleration during testing, the degree of rigidity of the structural elements of the aircraft is determined. A simple blow can cause destruction due to the occurrence of strong, albeit short-term overvoltages in the material. A complex blow can lead to the accumulation of microstrains of a fatigue nature. Since the design of the aircraft has resonant properties, even a simple shock can cause an oscillatory reaction in its elements, which is also accompanied by fatigue phenomena.

Mechanical overloads cause deformation and breakdown of parts, loosening of joints (welded, threaded and riveted), loosening of screws and nuts, movement of mechanisms and controls, as a result of which the adjustment and adjustment of devices change and other malfunctions appear.

The harmful effects of mechanical overloads are controlled in various ways: by increasing the structural strength, using parts and elements with increased mechanical strength, using shock absorbers and special packaging, and rational placement of devices. Protection measures from the harmful effects of mechanical overload are divided into two groups:

1. measures aimed at ensuring the required mechanical strength and rigidity of the structure;
2. measures aimed at isolating structural elements from mechanical stress.

In the latter case, various shock absorbing means, insulating gaskets, compensators and dampers are used.

The general task of testing aircraft for impact loads is to test the ability of the aircraft and all its elements to perform their functions during and after impact, i.e. maintain their technical parameters during impact and after impact within the limits specified in the regulatory and technical documents.

The main requirements for impact tests in laboratory conditions are the maximum proximity of the result of a test impact on an object to the effect of a real impact in full-scale operating conditions and reproducibility of impact.

When reproducing shock loading modes under laboratory conditions, restrictions are imposed on the pulse shape of instantaneous acceleration as a function of time (Fig. 2.50), as well as on the permissible limits of the pulse shape deviations. Almost every shock pulse at the laboratory bench is accompanied by a pulsation, which is a consequence of resonance phenomena in drum sets and auxiliary equipment. Since the spectrum of the shock pulse is mainly a characteristic of the destructive effect of the shock, even a slight pulsation superimposed can make the measurement results unreliable.

Testing installations simulating individual impacts with subsequent vibrations make up a special class of equipment for mechanical testing. Impact stands can be classified according to various criteria (Fig. 2.5!):

I - on the basis of the formation of a shock pulse;

II - by the nature of the tests;

III - by the type of reproducible shock loading;

IV - according to the principle of action;

V - by energy source.

In general terms, the shock stand scheme consists of the following elements (Fig. 2.52): a test object mounted on a platform or container together with a shock overload sensor; acceleration means to inform the object of the required speed; brake device; control systems; recording equipment for recording the studied parameters of the object and the law of change in shock overload; primary converters; auxiliary devices for adjusting the functioning modes of the test object; power sources necessary for the operation of the test object and recording equipment.

The simplest bench for shock tests in laboratory conditions is a bench working on the principle of dropping a test object fixed to the carriage from a certain height, i.e. using to disperse the force of Earth's gravity. The shape of the shock pulse is determined by the material and the shape of the colliding surfaces. Acceleration up to 80,000 m / s2 can be provided at such stands. In fig. 2.53, a and b show fundamentally possible schemes of such stands.

In the first version (Fig. 2.53, a), a special cam 3 with a ratchet tooth is driven into rotation by a motor. When the cam reaches the maximum height H, the table 1 with the test object 2 falls on the brake devices 4, which tell him the blow. Shock overload depends on the height of the fall H, the stiffness of the braking elements k, the total mass of the table and the test object M and is determined by the following dependence:

By varying this value, various overloads can be obtained. In the second version (Fig. 2.53, b), the stand works according to the method of dropping.

Test benches using a hydraulic or pneumatic drive to disperse the carriage are virtually independent of gravity. In fig. 2.54 shows two options for pneumatic impact stands.

The principle of operation of the stand with air gun (Fig. 2.54, a) is as follows. Compressed gas is supplied to the working chamber /. Upon reaching a predetermined pressure, which is controlled by a manometer, the automaton 2 for releasing the container 3 is activated, where the test object is located. When exiting the barrel 4 of the air gun, the container contacts the device 5, which allows you to measure the speed of movement of the container. The air gun through the shock absorbers is attached to the supporting posts b. The predetermined braking law on the shock absorber 7 is implemented by changing the hydraulic resistance of the flowing fluid 9 in the gap between the specially profiled needle 8 and the hole in the shock absorber 7.

The structural diagram of another pneumatic impact stand, (Fig. 2.54, b) consists of test object 1, carriage 2, on which the test object is installed, gaskets 3 and brake device 4, valves 5, which allow to create specified gas pressure drops on piston b, and gas supply systems 7. The brake device is activated immediately after the collision of the carriage and the gasket to prevent the carriage from returning and distorting the shapes of the shock pulse. Management of such stands can be automated. They can reproduce a wide range of shock loads.

As an accelerating device, rubber shock absorbers, springs, and, in some cases, linear induction motors can be used.

The capabilities of almost all shock stands are determined by the design of the brake devices:

1. The impact of the test object with a rigid plate is characterized by inhibition due to the occurrence of elastic forces in the contact zone. This method of inhibition of the test object allows to obtain large values \u200b\u200bof overloads with a small front of their growth (Fig. 2.55, a).

2. To obtain overloads in a wide range, from tens to tens of thousands of units, with their rise time from tens of microseconds to several milliseconds, deformable elements are used in the form of a plate or gasket lying on a rigid base. The materials for these gaskets can be steel, brass, copper, lead, rubber, etc. (Fig. 2.55, b).

3. To ensure any specific (predetermined) law of variation of n and m in a small range, deformable elements are used in the form of a tip (crasher), which is installed between the plate of the shock stand and the test object (Fig. 2.55, c).

4. To reproduce an impact with a relatively large path of braking, a brake device is used, consisting of a lead, plastically deformable plate located on the rigid base of the stand and a hard tip embedded in it of the corresponding profile (Fig. 2.55, d), mounted on the object or platform of the stand . Such braking devices make it possible to obtain overloads in a wide range of n (t) with a short rise time, reaching tens of milliseconds.

5. As a braking device, an elastic element in the form of a spring (Fig. 2.55, e) mounted on the moving part of the shock stand can be used. This type of braking provides relatively small overloads of a semi-sinusoidal shape with a duration measured in milliseconds.

6. A punched metal plate fixed along the contour at the base of the installation, in combination with a rigid tip of the platform or container, provides relatively small overloads (Fig. 2.55, f).

7. Deformable elements mounted on a movable platform of the stand (Fig. 2.55, g), in combination with a rigid conical trap provide long-term overloads with a rise time of up to tens of milliseconds.

8. The brake device with a deformable washer (Fig. 2.55, h) allows to obtain large braking paths of an object (up to 200 - 300 mm) with small washer deformations.

9. The creation in laboratory of intense shock pulses with large fronts is possible using a pneumatic brake device (Fig. 2.55, s). Among the advantages of a pneumatic damper are its reusable effects, as well as the ability to reproduce shock pulses of various shapes, including those with a significant predetermined front.

10. In the practice of conducting shock tests, the brake device in the form of a hydraulic shock absorber has been widely used (see Fig. 2.54, a). When the test object hits the shock absorber, its rod is immersed in liquid. The fluid is ejected through the stem point according to the law determined by the profile of the control needle. By changing the profile of the needle, it is possible to realize a different kind of law of inhibition. The needle profile can be obtained by calculation, but it is too difficult to take into account, for example, the presence of air in the piston cavity, the friction forces in the sealing devices, etc. Therefore, the calculated profile must be experimentally adjusted. Thus, by the calculation-experimental method, it is possible to obtain the profile necessary for the implementation of any law of inhibition.

Conducting a shock test in laboratory conditions puts forward a number of special requirements for the installation of the facility. So, for example, the maximum permissible movement in the transverse direction should not exceed 30% of the nominal value; both when testing for impact resistance, and when testing for impact strength, the product should be able to be installed in three mutually perpendicular positions with the reproduction of the required number of shock pulses. The single characteristics of the measuring and recording equipment should be identical in a wide frequency range, which ensures the correct registration of the ratios of the various frequency components of the measured pulse.

Due to the variety of transfer functions of various mechanical systems, the same shock spectrum can be caused by a shock pulse of various shapes. This means that there is no one-to-one correspondence between some temporal acceleration function and the shock spectrum. Therefore, from a technical point of view, it is more correct to set the technical conditions for impact tests, which contain requirements for the impact spectrum, and not for the temporal characteristic of acceleration. This primarily relates to the mechanism of fatigue failure of materials due to the accumulation of loading cycles, which can be different from test to test, although the peak values \u200b\u200bof acceleration and stress will remain constant.

When modeling the shock processes of the system of determining parameters, it is advisable to compile according to the identified factors necessary for a sufficiently complete determination of the desired value, which can sometimes be found only experimentally.

Considering the impact of a massive, freely moving rigid body on a relatively small deformable element (for example, on the brake device of the stand), mounted on a rigid base, it is necessary to determine the parameters of the impact process and establish the conditions under which such processes will be similar to each other. In the general case of the spatial motion of a body, six equations can be composed, three of which give the law of conservation of momentum, two the laws of conservation of mass and energy, and sixth is the equation of state. These equations include the following quantities: three velocity components Vx Vy \\ Vz\u003e density p, Pressure p and entropy. Neglecting dissipative forces and considering the state of the deformable volume to be isentropic, one can exclude entropy from the number of determining parameters. Since only the motion of the center of mass of the body is considered, it is possible not to include velocity components Vx, Vy among the determining parameters; Vz and the coordinates of the points A, Y, Z inside the deformable object. The state of the deformable volume will be characterized by the following determining parameters:

• the density of the material p;
• pressure p, which is more appropriate to take into account through the maximum local strain and Otmax, considering it as a generalized parameter of the force characteristic in the contact zone;
• the initial impact velocity V0, which is directed normal to the surface on which the deformable element is mounted;
• current time t;
• body weight t;
• acceleration of gravity g;
• the elastic modulus of materials E, since the stress state of the body upon impact (with the exception of the contact zone) is considered elastic;
• characteristic geometrical parameter of the body (or deformable element) D.

In accordance with the mc theorem, of eight parameters, among which three have independent dimensions, five independent dimensionless complexes can be composed:

The dimensionless complexes composed of the determined parameters of the impact process will be independent of some functions] dimensionless complexes P1 - P5.

The parameters to be determined include:

• current local deformation a;
• body speed V;
• contact force P;
• tension inside the body a.

Therefore, we can write the functional relationships:

The form of the functions / 1, / 2, / e, / 4 can be established experimentally, taking into account a large number of determining parameters.

If during impact in the sections of the body outside the contact zone no residual deformations appear, then the deformation will be local in nature, and, therefore, the complex H5 \u003d pU ^ / E can be eliminated.

The complex Jl2 \u003d Pttjjjax) ~ Cm is called the coefficient of relative body mass.

The coefficient of resistance to plastic deformation Cp is directly related to the force characteristic N (the coefficient of material compliance, depending on the shape of the colliding bodies) with the following dependence:

where p is the reduced density of materials in the contact zone; Cm \u003d t / (pa?) Is the reduced relative mass of the colliding bodies, which characterizes the ratio of their reduced mass M to the reduced mass of the deformable volume in the contact zone; xV is a dimensionless parameter characterizing the relative work of deformation.

The function Cp - / s (R1 (R1, R3, R4) can be used to determine the overloads:

If we ensure the equality of the numerical values \u200b\u200bof the dimensionless complexes IJlt Я2, Я3, Я4 for two shock processes, then these conditions, i.e.

will be similarity criteria for these processes.

When these conditions are fulfilled, the numerical values \u200b\u200bof the functions fj / g./z »» »te will be the same at similar instants of time -V CtZoimax- const; ^ r \u003d const; Cp \u003d const, which allows one to determine the parameters of one shock process by simply recalculating the parameters of another process. The necessary and sufficient requirements for physical modeling of shock processes can be formulated as follows:

1. The working parts of the model and the full-scale object should be geometrically similar.
2. Dimensionless complexes composed of defining steam, meters, must satisfy the condition (2.68). Introducing scale factors.

It must be borne in mind that when modeling only the parameters of the shock process, the stressed states of bodies (natures and models) will be necessarily different.

12 steps to increase impact speed

Speed. Blinding, mesmerizing, speed is perhaps the most coveted and spectacularly impressive mastery in martial arts. Bruce Lee’s lightning strikes created his reputation. The speed is inherent in most of the outstanding professional boxers, such as Sugar Ray Leonard and Muhammad Ali. Ali's strength was only adequate to his physique, while the speed of the blow was simply phenomenal. And Leonard's hands were probably the fastest of all that the world has ever seen. Also, former full-contact karate champion Bill Wallace never had a great punching power, but lightning kicks won him a professional record in the ring, which has not yet been broken.

Is this magical power incorporated in human genes, or can it be acquired and increased through training? According to dr. John LaTurrett, the holder of the black belt in kenpo karate and his doctorate in sports psychology, anyone can become “the fastest” if he follows several basic principles.

“90% speed training is psychological, or maybe 99%,” LaTurrett says. This psychological approach to training seems to have brought results to 50-year-old karate instructors from Medford, Oregon. It was officially recorded that he managed to make 16.5 hits in one second, and he claims that his students can do this even faster. Following the 12 steps of the program to increase speed.

1. LEARN BY OBSERVING SPECIALISTS.   “If a person wants to be a fast runner, but doesn’t leave home, then he learns to be a cripple in a wheelchair,” says LaTurrett. “All he needs to do is leave the house, find a fast runner of his age, strength and physiology of the body and study his movements, doing exactly what he does.”

2. USE SMOOTH, FLOWING SHOCKS. The flowing Chinese-style striking technique has a much greater explosive power than traditional reverse strikes in karate and boxing, says LaTurrett, because the speed of the impact is generated by the pulse. You can train your brain and nervous system for quick strikes. To achieve this, perform a “smooth” exercise consisting of a sequence of movements, starting with three to four strokes at a time. As soon as you start doing this combination automatically, add a little more movement, then a little more, until your subconscious mind learns to link each individual movement into one stream, similar to a waterfall. After some time, you can make 15-20 full movements in one or even less seconds.

3. USE FOCUSED AGGRESSION. You must learn to instantly switch from a passive state to a state of alert in order to attack before the enemy can predict your actions. Any doubt about your ability to protect yourself should be eradicated by psychological preparation before you become stressed.

The reaction time to any action is divided into three phases - perception, decision and action - which together takes approximately sixth of a second. To accept information and make appropriate decisions should be in a relaxed state, so as not to give a hint to the enemy about your subsequent actions. Once you are focused, you can attack so quickly that your opponent does not have time to blink an eye.

To correctly perform this type of attack, you must be absolutely sure of your correctness and ability to act correctly, otherwise you will lose. As La Turrett himself puts it: "Chatting, don't cook rice." You must be aggressive and confident in your skills. Self-confidence should be born in a battle with a real opponent to a greater extent than when performing a kata, where you attack an imaginary opponent.

You must also maintain a constant state of readiness, carefully monitor the events taking place around you, be ready at any time, in case of danger, to realize potential strength. This special physical, mental and emotional state can be mastered by any person, but only in conditions of direct confrontation with the enemy.

Once you have reached this level of training, analyze and try to categorize your feelings. Later, in a duel, you can learn from your experience that will give you a clear advantage over your opponent.

Ask yourself the following questions: What particularly distracts me? Maybe the distance between me and the enemy? Or his undisguised malice towards me? His manner of expression? What attention does this mental state have on me? What are my feelings? What did I look like? What was my facial expression? What muscles were tense? Which ones are relaxed? What did I say to myself while in this state? (It would be best if you did not “mutter” something to yourself there.) What mental images did I have? What was my visual focus on?

After you find answers to your questions, reproduce the situation again, try to make sensations, surroundings and sounds again brightly appear in your brain. Repeat this over and over until you are able to enter yourself into this mental state at any moment.

4. USE READY STANDS WHICH CAN GIVE YOU AN OPPORTUNITY OF CHOICE.   One of the secrets of Wallace's success was that he could instantly perform a side kick, a circular kick and a reverse circular kick with the same accuracy from one single foot position. In a word, your stance should give you the opportunity to make chopping punches, claw-style punches, elbows, shocks or hammer strikes, depending on the opponent’s actions.

Use the military equipment that you think is most suitable for you. Learn to take a position from which you only need to make a slight movement to move from one target to another. The selection of a natural (natural) combat position eliminates the need to choose a stance and allows you to catch the enemy by surprise. And the puzzled opponent is already half defeated.

5. BEWARE THE PSYCHOLOGY OF ONE DEATH BLOW.   This is the conclusion of rule number one. Your initial attack should be a sequence of three hits, even if the first strike was able to stop the attacking opponent. The first hit is a “snack”, the second is a “main course”, well, and the third is a “dessert”.

While an unsuspecting adversary is preparing for a direct or “back” kick, ”says LaTurrett,“ you can blindfold him with a slap in the eyes, punch the temple with your left hand, and use your right elbow to hit the other temple. Then you can hit him with your right elbow in the jaw, and with your left hand in the eyes. Get down on your knees and hit with your right fist in the groin, and with two fingers of your left hand - over the eyes of the enemy. This is the end of this story. ”

6. USE VISUALIZATION EXERCISES.   When practicing exercises on developing the speed of impact, you should think that you are doing the blows at the speed you want. “If you don’t see, you cannot do it,” LaTurrett says. Such psychological preparation in many ways complements the physical.

Visualization is not as complicated as many people think. Try the following experiment: stop right now and describe to yourself the color of your car. Then an orange. Then your best friend. How did you manage to describe all this? You IMAGINED them yourself.

Many people do not know that they often create “images” in their head at the sub-podcast level. The part of the brain that is responsible for creating and reproducing images can be fine-tuned even if they are not used to accessing it.

Once you have learned to imagine yourself in a real battle, try to see and feel that your actions are reaching your goals. Feel your bended knees add power to your bumps. Feel the kick of your foot on the ball while hitting, etc.

7. IDENTIFY OPEN TARGETS.   In order to learn to identify open targets and predict the actions of the enemy, you need to train with a real opponent. Feelings of synchronism can be achieved by repeatedly reproducing attacks until you have a firm belief that you can use it in a real battle.

One of the reasons why boxers have such a good strike speed is that they practice their technique thousands of times in sparring. And when a goal arises in front of them, they don’t think, they ACT. This subconscious skill can be easily acquired, but there is no shortcut to this. You must train again and again until your actions become instinctive.

8. DO NOT “TELEGRAPH” YOUR ACTIONS. It does not matter how fast you are, because if your opponent predicted your actions, you are no longer fast enough. You can believe it or not, it’s more difficult for your opponent to see a blow that goes at the level of his eyes than a circular blow from the side.

Hitting a hook (not a circular, but a hook) requires a lot more movement and is much easier to block. In a word, a correctly hit to the nose bridge can hit the enemy before he realizes that you hit him. First of all, do not give out your intentions by clenching your fists, moving your shoulder or taking a deep breath before striking.

Once you have mastered the physical structure of the exercise technique, practice taking advantage of the limitations of a person’s perception, trying to take a position that limits the adversary’s ability to see and predict your actions. This skill requires a lot of practice, but as soon as you learn it, you will be able to attack the enemy, almost with impunity.

9. USE THE RIGHT RESPIRATORY TECHNIQUE.   During the fight, many athletes hold their breath, causing themselves great harm. The body becomes tense, as a result of which the speed and strength of your strokes decreases. Kiai during the execution of the technique even harms you, because it dampens your momentum. The key to high speed blows is that you must exhale air in accordance with the blows.

10. SUPPORT GOOD PHYSICAL FORM.   Flexibility, strength and endurance play a crucial role in self-defense, even though most street fights last for a second. If your body is both flexible and relaxed, then you can strike at almost any angle, hitting high and low targets without an uncomfortable change of stance. Also, the strength of the legs is extremely important. The stronger your legs will be, the stronger your blow will be, and the faster you can reduce the distance between you and your opponent. It is important to increase the strength of the arms and forearms by training with weights and special exercises for bumps. Exercise will help you strengthen your palms and wrists, improve accuracy and penetration of bumps.

11. BE RESISTANT.   You must commit yourself three times a week for 20-30 minutes to try to significantly improve the speed of impact. Be prepared for the fact that inevitably there will come periods when it will seem to you that you are not making significant progress. Most people experience five levels of feelings of progress or lack of visible results during training.

There is “unconscious incompetence” (literally) when you are not aware of the problem and how to solve it.

This is the point where you realize that your knowledge and skills are insufficient, and you begin to look for ways to solve the problem. “Unconscious incompetence” means that you can perform new exercises only when your attention is extremely focused.

This is the most difficult stage of orientation, and it seems to you that it will last for ages. The process of transforming consciousness into reflective actions takes approximately 3,000 to 5,000 repetitions. “Unconscious incompetence” is the only skill level when true speed becomes attainable. While you learn to respond instinctively. This level can only be achieved through thousands of repetitions of technology. Most people are in this reflective or automatic mental state when they drive their car, which allows them to react to traffic troubles with unconscious composure, they do not think about how to shift gears or apply the brake. You will not be able to increase the speed of impact until your basic movements are based on reflexes. The final stage of mastery is “the consciousness of your unconscious incompetence,” the point that only a few people have managed to reach all the time.

12. KEEP A NATURAL, RELAXED, BALANCED RACK.   The best fighting stance is one that doesn't look like a fighting stance. As the legendary Japanese sword master Musashi Miyamoto has precisely noted, “Your fighting stance becomes your daily stance, and your daily stance becomes fighting”. You must know exactly which techniques you can apply from each position, and must be able to perform them naturally, without hesitation or change of stance.

Practice these 12 principles every day for 20 minutes. After a month of training, you will improve a new, crushing speed. LaTurrett says: “There are no fast fighters by nature. Everyone had to train just like you. The harder you train, the less vulnerable you are in battle. ”

Take a look at the dictionary of foreign words: “impulse” - from lat. impulsus - push, strike, motivation. " The effect produced by the blow has always been surprising in humans. Why is a heavy hammer laid on a piece of metal on the anvil only presses it against the support, and the same hammer crushes the metal with a hammer blow? And what is the secret of the old circus trick when the crushing blow of a hammer on a massive anvil does no harm to the person on whose chest this anvil is installed? What is the mistake in the question that one student once asked: “What is the impact force when a load of 20 kg falls from a height of 10 m?” And what does the expression “impact force” mean?

Galileo was also interested in the problem of “amazing impact force”. He describes the witty experience with which he tried to determine the "strength of the blow." The experience consisted of the following: two buckets were suspended from one end, and a load (stone), balancing them, from one end to a solid beam mounted horizontally on an axis like a beam of a balance (Fig. 39). The upper bucket was filled with water; a hole closed by a cork was made in the bottom of this bucket.

If you remove the cork, then the water will pour into the lower bucket and the force of the impact of the jet on the bottom of this bucket, it would seem, will cause the right side of the rocker to fall. Adding the appropriate load on the left will restore equilibrium, and its mass will allow you to assess what the impact force of the jet is.

However, to Galileo's surprise, experience showed a completely different thing. At first, as soon as the cork was removed and the water began to pour out, not the right but the left part of the rocker arm fell. And only when the jet reached the bottom of the lower bucket, the balance was restored and was no longer disturbed until the end of the experiment.

How to explain this "strange" result? Is it wrong with Galileo's first assumption that the jet, striking the bottom of the lower bucket, will cause it to sink? To understand this rather complex issue, you need to know the law of conservation of momentum, which, together with the law of conservation of energy, refers to the greatest laws of nature.

The term “quantity of movement” was introduced by Galileo's contemporary, the French philosopher and mathematician Descartes, but he was introduced far from a scientific basis, but from metaphysical (not based on experience) religious ideas of the philosopher. The indefinite, foggy term “momentum” is now replaced by the term “momentum”.

In the previous conversation, we cited Newton’s second law in the form that Newton himself gave him: "The change in the momentum is proportional to the driving force and occurs in the direction of the straight line along which this force acts."

Newton was the first to introduce the concept of mass into mechanics and, using it, gave an exact definition of the quantity of motion as the product of the mass of a body and its velocity (mv).

If the initial speed v 0 of a body of mass m under the influence of any force during time t increases to v 1, then the change in momentum per unit time will be:

  This change is proportional to the applied force F:

mv 1 - mv 0 \u003d Ft

This is Newton’s second law. It follows from it that the same change in the momentum can occur both with the prolonged action of a small force and with the short-term action of a large force. The product Ft can be considered as a measure of the force. It is called the impulse of power. Do not mix only the impulse of force with the force itself, as well as with the impulse. It can be seen from the above formula that the momentum of a force is not equal to the momentum itself, but to the change in momentum. In other words, the momentum of the force over time t is equal to the change in the momentum of the body during this time. Momentum is usually denoted by the letter p:

In the general case, it should be taken into account that the momentum is a vector physical quantity:

  We have already mentioned the two greatest laws of nature: the law of conservation of momentum and the law of conservation of energy. These laws are conveniently demonstrated by the example of a blow. The phenomenon of shock is of great importance in science and technology. Consider this phenomenon more carefully.

We distinguish between elastic and inelastic materials. For example, a rubber ball is resilient; this means that after the termination of the deforming force (compression or tension), it again returns to its original form. On the contrary, a piece of clay crumpled by hand does not return to its original form. Rubber, steel, marble, bone are elastic materials. You can easily see the elasticity of the steel ball by dropping it from a certain height onto the elastic support. If the ball was previously smoked, then the trace will remain on the support not in the form of a dot, but in the form of a sufficiently distinguishable speck, since the ball crumpled upon impact, although then, having rebounded, it regained its shape. The support is also deformed. The elastic force arising in this case acts on the ball from the support side and gradually decreases its speed, informing it of upward acceleration. In this case, the direction of the speed of the ball changes to the opposite and it takes off above the support to the same height from which it fell (ideal case with perfect elasticity of the colliding bodies). The support itself, as connected with the Earth having a huge mass, practically remains motionless.

Successive changes in the shape of the ball and the surface of the support for different times are shown in Figure 40. The ball falls from a height h and at the moment of landing (position in the figure) has a speed directed vertically downward. In position B, the deformation of the ball is maximum; at this moment, its speed is zero, and the force F acting on the ball from the side of the support plane is maximum: F \u003d F max. Then the force F begins to decrease, and the speed of the ball grows; point C corresponds to the moment when the speed value. In contrast to state A, now the speed is directed vertically upward, as a result of which the ball takes off (jumps) to a height h.

Suppose that an elastic ball moving at a certain speed collides with a stationary ball of the same mass. The action of a stationary ball is again reduced to a decrease in the speed of the first ball and its stopping. At the same time, the first ball, acting on the second, tells him the acceleration and increases its speed to its original speed. Describing this phenomenon, they say that the first ball transmitted its momentum to the second. You can easily verify this experimentally with two balls suspended on threads (Fig. 41). Measuring the speed with which the balls move is, of course, difficult. But you can use the well-known position that the speed acquired by the falling body depends on the height of incidence (). Apart from small energy losses due to the incomplete elasticity of the balls, ball 2 will take off from the collision with ball 1 to the same height as ball 1 fell. Moreover, ball 1 will stop. The sum of the momenta of both balls thus remains constant all the time.


  It can be proved that the law of conservation of momentum is observed in the interaction of many bodies. If external bodies do not act on the system of bodies, then the interaction of bodies inside such a closed system cannot change its total momentum. You can now “scientifically” refute the boastful tales of Baron Munchausen, who claimed that he managed to pull himself out of the swamp by his own hair.

Returning to the famous Galileo experiment with which we began our conversation, we will not be surprised at the result of the experiment: in the absence of external forces, the momentum of the entire system could not change and therefore the beam remained in balance, despite the impact of the jet on the bottom of the second bucket. A detailed mathematical analysis of the experiment is rather complicated: it is necessary to calculate the decrease in mass of the upper bucket, from which a stream of water is poured out, the reaction of the leaky jet, and, finally, the impulse reported to the bottom of the lower bucket by a jet strike. The calculation shows that the sum of all impulses, taking into account their signs, is equal to zero, as was the case before the cork was pulled out, and the whole system — a beam, buckets, counterweight — remains in equilibrium.

The law of conservation of momentum and the law of conservation of energy are the basic laws of nature. We note, however, that the conservation of momentum in mechanical processes is always and unconditionally valid, while applying the law of conservation of energy in mechanics, one must be careful (it requires certain conditions to be satisfied). "Can not be! “You will exclaim indignantly,“ the law of conservation of energy is valid always and everywhere! ” And I don’t argue, read on. Let us consider an example of a collision of elastic and inelastic balls.

Bounce. Let a ball weighing 2 kg move at a speed of 10 m / s to hit a second (motionless) ball of the same mass. As we already know, after the impact, the first ball will stop, and the second will move at the speed of the first ball before the collision.

Check the law of conservation of momentum:

  Law of energy conservation:

  Both laws are observed.

Inelastic impact (balls made of soft clay or putty). After the impact, the stuck together balls continue to move together, but at a speed half that of the first ball before the impact.

The law of conservation of momentum:

  The law is respected.

Law of energy conservation:

  Before the impact, the energy was 100 J, and after the impact, 50 J! Where did half the energy go? You probably guessed: the mechanical energy equal to 50 J turned into internal energy: after the impact, the molecules began to move more briskly - the balls heated up. If we could take into account all types of energy before and after the impact, we would be convinced that even in the case of an inelastic impact, the energy conservation law is not violated. The law of conservation of energy is always valid, but one must take into account the possibility of converting energy from one type to another. In practical cases, the application of the laws of conservation of energy and momentum is especially important. Consider a few examples of the application of these laws.

Forging products in the forge shop. The purpose of the forging is to change the shape of the product using hammer blows. For the best use of the kinetic energy of the falling hammer, it is necessary to lay the product on a large anvil. Such an anvil will receive a negligible speed, and most of the energy upon impact will turn into deformation energy (the shape of the product will change).

Pile driving. In this case, it is desirable to transfer most of the kinetic energy to the pile so that it can do the job of overcoming the soil resistance and go deeper into the soil. The mass of the pile driver, i.e., the load that falls on the pile, should be greater than the mass of the pile. In accordance with the law of momentum, the pile speed will be higher in this case and the pile will go deeper into the ground.

On the power of impact. The task set at the beginning of our conversation does not indicate the duration of the strike, and the latter depends on the nature of the support. With a rigid support, the duration of the impact will be less, and the average force of the impact is longer; with soft support, vice versa. The net, stretched under the trapezoid in the circus, protects the air gymnast from a strong blow when falling. A footballer, taking a hit of the ball, should be sent back, thereby increasing the duration of the strike - this will soften the kick. There are many such examples. In conclusion, we will examine another interesting problem, which after all of the above will be clear to you.

“Two boats move by inertia in the calm water of the lake towards each other in a parallel course at a speed of v 1 \u003d 6 m / s. When they caught up, the cargo was quickly transferred from the first boat to the second. After that, the second boat continued to move in the same direction, but with a speed of v 2 \u003d 4 m / s.

Determine the mass M 2 of the second boat if the mass M 1 of the first without load is 500 kg and the mass m of the load is 60 kg. Calculate the energy reserve of boats and cargo before and after shifting the cargo. Explain why this energy reserve has changed. ”

Decision. Before meeting, the momentum of the first boat is: (M 1 + m) v 1, and the momentum of the second boat: M 2 v 1.

When transferring cargo from the first boat to the second, the speed of the first boat does not change, since it experiences a push in the lateral direction (recoil), which cannot overcome the resistance of water. The speed of the second boat changes, since the transferred cargo must sharply change the direction of its speed in the opposite direction, which can be considered as a push.

Applying the law of conservation of momentum, we write:


  Energy decreased by 3500 J. Where did the energy go? The lost part of the mechanical energy turned into internal energy (heat) when the speeds of the load and the second boat were aligned.

An attempt to analyze the trauma of blows to the head with a bare fist, compared with punches in a boxing glove.

Shock theory.

A shock in mechanics is a short-term interaction of bodies, as a result of which their velocities change. Impact force depends, according to Newton's law, on the effective mass of the striking body and its acceleration:

Fig. 1 Impact force development curve over time

F \u003d m * a (1),

where
  F is power
  m is the mass
  a is the acceleration.

If we consider the impact in time, then the interaction lasts a very short time - from ten thousandths (instantaneous quasi-elastic impacts) to tenths of a second (inelastic impacts). The shock force at the beginning of the impact increases rapidly to the highest value, and then drops to zero (Fig. 1). Its maximum value can be very large. However, the main measure of the impact interaction is not force, but the impact moment, numerically equal to the area under the curve F (t). It can be calculated as an integral:

(2)

where
  S is the shock pulse,
  t1 and t2 - time of the beginning and end of the impact,
  F (t) is the dependence of the shock force F on time t.

Since the collision process lasts a very short time, in our case it can be considered as an instantaneous change in the velocities of the colliding bodies.

In the process of impact, as in any natural phenomena, the law of conservation of energy must be observed. Therefore, it is natural to write the following equation:

E1 + E2 \u003d E’1 + E’2 + E1p + E2p (3)

where
  E1 and E2 are the kinetic energies of the first and second bodies before impact,
  E’1 and E’2 are kinetic energies after impact,
  E1p and E2p are the energy of impact loss in the first and second bodiese.

The relationship between kinetic energy after impact and loss energy is one of the main problems of impact theory.

The sequence of mechanical phenomena upon impact is such that, first, the deformation of the bodies occurs, during which the kinetic energy of motion passes into the potential energy of elastic deformation. Then the potential energy goes back to kinetic. Depending on which part of the potential energy goes into kinetic and which is lost, dissipated by heating and deformation, three types of impact are distinguished:

1. Absolutely resilient punch   - all mechanical energy is conserved. This is an idealized model of collision, however, in some cases, for example, in the case of billiard balls, the picture of collision is close to absolutely elastic impact.
2. Absolutely Inelastic Impact   - the deformation energy is completely converted into heat. Example: landing in jumps and bounces, hitting a ball from plasticine into a wall, etc. With an absolutely inelastic impact, the velocities of the interacting bodies are equal after the impact (the bodies stick together).
3. Partially Inelastic Impact - part of the energy of elastic deformation passes into the kinetic energy of motion.

In reality, all impacts are either absolutely or partially inelastic. Newton proposed characterizing the inelastic impact by the so-called recovery coefficient. It is equal to the ratio of the velocities of the interacting bodies after and before the impact. The smaller this coefficient, the more energy is spent on the non-kinetic components E1p and E2p (heating, deformation). Theoretically, this coefficient cannot be obtained, it is determined empirically and can be calculated by the following formula:

where
  v1, v2 - the speed of the bodies before the impact,
  v’1, v’2 - after the strike.

At k \u003d 0, the impact will be absolutely inelastic, and at k \u003d 1, it will be absolutely elastic. The recovery coefficient depends on the elastic properties of the colliding bodies. For example, it will be different when a tennis ball hits different soils and rackets of different types and qualities. The recovery coefficient is not just a characteristic of the material, since it also depends on the speed of impact interaction - with an increase in speed it decreases. The directories give values \u200b\u200bof the recovery coefficient for some materials for impact speeds of less than 3 m / s.

Impact Biomechanics

Percussion in biomechanics refers to actions whose result is achieved by mechanical shock. In percussion actions distinguish:

1. Swing   - the movement preceding the shock movement and leading to an increase in the distance between the shock link of the body and the object to strike. This phase is the most variable.
2. Shock motion   - from the end of the swing to the start of the strike.
3. Impact interaction (or actually impact)   - collision of impacting bodies.
4. Aftershock movement- the movement of the shock link of the body after the termination of contact with the subject, which struck.

With a mechanical impact, the speed of the body (for example, the ball) after the impact is higher, the greater the speed of the impacting link immediately before the impact. In sports, such a relationship is not necessary. For example, when serving in tennis, an increase in the speed of movement of the racket can lead to a decrease in the speed of departure of the ball, since the shock mass during strokes performed by an athlete is variable: it depends on the coordination of his movements. If, for example, a strike is performed by bending the hand or with a relaxed hand, then only the mass of the racket and hand will interact with the ball. If, at the moment of impact, the striking link is fixed by the activity of antagonist muscles and is, as it were, a single solid body, then the mass of this link will take part in the shock interaction.

Sometimes an athlete strikes two blows at the same speed, and the ball’s relegation speed or impact force is different. This is due to the fact that the shock mass is not the same. The magnitude of the impact mass can be used as a criterion for the effectiveness of the impact technique. Since it is quite difficult to calculate the impact mass, the effectiveness of the impact interaction is estimated as the ratio of the velocity of the projectile after impact and the speed of the impact element before impact. This indicator is different in strokes of different types. For example, in football, it varies from 1.20 to 1.65. It depends on the weight of the athlete.

Some athletes who own a very strong blow (in boxing, volleyball, football, etc.) do not differ in great muscle strength. But they are able to communicate greater speed to the striking segment and, at the moment of impact, interact with the striking body by a large shock mass.

Many percussion sports cannot be regarded as a “pure” kick, the basis of the theory of which is described above. In the theory of impact in mechanics, it is assumed that the impact occurs so quickly and the impact forces are so great that all other forces can be neglected. In many shock actions in sports, these assumptions are not justified. The impact time in them, although small, is nevertheless impossible to neglect; the impact interaction path, along which colliding bodies move together during the impact, can reach 20-30 cm.

Therefore, in sports shock actions, in principle, it is possible to change the amount of movement during a collision due to the action of forces not related to the impact itself. If the impact unit during the impact is additionally accelerated due to muscle activity, the impact momentum and, accordingly, the projectile departure speed increase; if it is braked arbitrarily, the shock impulse and the departure speed decrease (this is necessary for accurate shortened strokes, for example, when passing the ball to a partner). Some shock movements, in which the additional increase in momentum during a collision is very large, are generally a cross between throwing and striking (this is how they sometimes perform second gear in volleyball).

The coordination of movements with the strongest blows obeys two requirements:

1. the message of the highest speed to the striking link by the moment of contact with the striking body. In this phase of movement, the same methods of increasing speed are used as in other moving actions;
2. increase in shock mass at the time of impact. This is achieved by “fixing” the individual links of the striking segment by simultaneously activating the antagonist muscles and increasing the radius of rotation. For example, in boxing and karate, the power of the blow with the right hand is approximately doubled if the axis of rotation passes near the left shoulder joint, compared with strokes in which the axis of rotation coincides with the central longitudinal axis of the body.

The impact time is so short that it is already impossible to correct the mistakes made. Therefore, the accuracy of the strike is decisively ensured by the correct actions during the swing and shock movement. For example, in football, the place of setting the supporting leg determines for beginners the target accuracy of about 60-80%.

Sports tactics often require strikes that are unexpected for the opponent (“hidden”). This is achieved by performing strokes without preparation (sometimes even without a swing), after fraudulent movements (feints), etc. The biomechanical characteristics of strokes change, since they are performed in such cases usually due to the action of only distal segments (wrist strokes).

  Distal - [e.g. end, phalanx] (distalis) - the end of a muscle or bone of a limb or the whole structure (phalanx, muscle) farthest from the body.

A kick in a boxing glove and without.

Recently, in some sports circles, serious debate has flared up over more traumatic brain injuries in a boxing glove than blows with a bare hand. We will try to get an answer to this question using the available research data and elementary laws of physics.

Where could such thoughts come from? I dare to suggest that it is mainly from observations of the process of hitting a boxing bag. Studies were conducted in which Smith and Hemil, in his 1986 paper, measured the athlete’s fist speed and the speed of a boxing bag. Strictly speaking, the risk of concussion is determined by the magnitude of head acceleration, not speed. However, the reported speed of the bag can only indirectly judge the magnitude of the acceleration, because it is assumed that this speed was developed in a short period of time impact.

Blows on the bag were carried out in three different ways: with a bare fist, in a glove for karate and in a glove for boxing. Indeed, the speed of the bag when hit with a glove was about 15% higher than when hit with a fist. Consider the physical background of the study. As mentioned above, all impacts are partially inelastic and part of the energy of the shock element is spent on the permanent deformation of the projectile, the rest of the energy is spent on communicating kinetic energy to the projectile. A fraction of this energy is characterized by a recovery coefficient.

For the sake of clarity, we immediately make a reservation that when considering the strain energy and the energy of translational motion, the large strain energy plays a positive role, since less translational energy remains. In this case, we are talking about elastic deformations that are not dangerous to health, while the energy of translational motion is directly related to acceleration and is dangerous to the brain.

We calculate the recovery coefficient of the boxing bag according to the data obtained by Smith and Hemil. The mass of the bag was 33 kg. The experimental results showed insignificant differences in fist speed for different types of gloves (bare fist: 11.03 ± 1.96 m / s, in a karate glove: 11.89 ± 2.10 m / s, in a boxing glove: 11.57 ± 3.43 m / s). The average fist velocity was 11.5 m / s. Differences in bag momentum were found for different types of gloves. A blow in a boxing glove caused a greater momentum of the bag (53.73 ± 15.35 N s) than a blow with a bare fist (46.4 ± 17.40 N s) or in a karate glove (42.0 ± 18.7 N s), which had almost equal values. To determine the speed of the bag by its momentum, you need to divide the momentum of the bag by its mass:

v \u003d p / m (5)

where
  v is the speed of the bag,
  p is the momentum of the bag,
  m is the mass of the bag.

Using the formula for calculating the recovery coefficient (4) and assuming that the speed of the fist after the strike is equal to zero, we obtain a value for striking with the bare fist of about 0.12, i.e. k \u003d 12%. For a case with a boxing glove, k \u003d 14%. This is confirmed by our life experience - a blow to a boxing bag is almost completely inelastic and almost all of the impact energy is spent on its deformation.

It should be noted separately that the fist had the highest speed in a karate glove. The momentum of the bag when it was hit by a karate glove was the smallest. Bare punch rates in this study were intermediate. This can be explained by the fact that the athletes were afraid to hurt the arm and reflexively reduced the speed and power of the blow. When struck in the karate glove, such fear did not arise.

And what will happen when hit in the head? Let us turn to another study by Valilko, Viano, and Bira for 2005, in which boxing gloves with gloves were studied on a specially designed dummy (Fig. 2). In this work, all impact parameters and impact on the mannequin's head and neck were investigated in detail. The neck of the mannequin was an elastic metal spring, so this model can be considered as a model of a boxer ready to hit with tight neck muscles. We will use the data on the forward movement of the dummy’s head and calculate the recovery coefficient (k) for a direct hit to the head.

Fig. 2 Exploration of Valilco, Viano and Bira - a boxer strikes a mannequin.

The average speed of the hand before impact was 9.14 m / s, and the average speed of the head after impact was 2.97 m / s. Thus, according to the same formula (4), the recovery coefficient k \u003d 32%. This means that 32% of the energy went into the kinetic movement of the head, and 68% went into the deformation of the neck and gloves. Speaking of neck strain energy, this is not about geometric deformation (curvature) of the cervical spine, but about the energy expended by the neck muscles (in this case, the spring) to keep the head stationary. In fact, this is the energy of resistance to shock. About the deformation of the face of the mannequin, as well as the facial skull of a person, there can be no question. Human bones are very strong material. In the table. Figure 1 shows the coefficient of elasticity (Young's modulus) of several materials. The larger this coefficient, the stiffer the material. The table shows that the stiffness of the bone is slightly inferior to concrete.

Table 1. Elastic coefficients (Young's moduli) of different materials.

What will be the recovery coefficient for a blow to the head with a bare fist? There are no studies on this subject. But let's try to figure out the possible consequences. When struck with a fist, just like with a glove, most of the energy will be taken over by the muscles of the neck, provided, of course, that they are tense. In the work of Valilko, Viano and Bira, it is impossible to separate the energy of deformation of the glove from the energy of deformation of the neck of a mannequin, but it can be assumed that the lion's share of the total energy of deformation went into the deformation of the neck. Therefore, it can be considered that when struck with a bare fist, the difference in the recovery coefficient will not exceed 2-5% compared with a gloved blow, as was the case in Smith and Hemil, where the difference was 2%. Obviously, a 2% difference is not significant.

The above calculations were done on the basis of data on the linear acceleration of the head after an impact. But for all their relative complexity, they are very far from predicting the invasiveness of the impact. The English physicist Holborn, who worked with gel models of the brain in 1943, was one of the first to put forward rotational acceleration of the head as the main parameter of brain injury. In the work of Ommaya et al., It is stated that a rotational acceleration of 4,500 rad / s2 leads to concussion and serious axonal injuries. An earlier work by the same author states that rotational acceleration above 1800 rad / s2 creates a 50% chance of concussion. The article by Valilko, Viano and Bira gives the parameters of 18 different strokes. If we take the same boxer and his punch at a speed of 9.5 m / s and a punch at 6.7 m / s, then in the first case, the recovery coefficient is 32%, and in the second it is 49%. According to all our calculations, it turns out that the second blow is more traumatic: a larger recovery coefficient (more energy went into the translational movement of the head), a large effective mass (2.1 kg and 4.4 kg), a slightly larger head acceleration (67 g and 68 g ) However, if we compare the rotational acceleration of the head produced by these two blows, we will see that the first blow is more traumatic (7723 rad / s2 and 5209 rad / s2, respectively). Moreover, the difference in numbers is quite significant. This fact indicates that the impact morbidity depends on a large number of variables and it is impossible to be guided by only one impulse p \u003d mv, evaluating the impact efficiency. The place of impact plays a great role here, so as to cause the greatest rotation of the head. In connection with the above data, it turns out that the boxing glove factor in injuries and concussions plays far from the main role.

To summarize our article, we note the following. The factors affecting brain injuries during a hit in a boxing glove and without it do not differ significantly and can change one way or the other, depending on the boxer and the type of impact. Much more significant factors affecting concussion lie outside the plane under consideration, such as the type and place of the blow to the head, which determines its rotational moment.

However, one should not forget that boxing gloves are designed primarily for the protection of soft tissues of the face. Hitting without gloves leads to damage to the bones, joints and soft tissues of both the attacker and the attacked athlete. The most common and painful of these is an injury called a “boxer knuckle”.

  Boxer knuckle is a term known in sports medicine used to describe a hand injury - damage to the joint capsule of the metacarpophalangeal joint (usually II or III), namely the fibers that hold the tendon of the extensor muscle.

The danger of infection with various infections, including hepatitis C or HIV viruses and a host of other unpleasant consequences, including an unattractive appearance, in every possible way reject the thesis that fighting with bare hands is safer for health.

References:

1. Lamash B.E. Lectures on biomechanics. https://www.dvgu.ru/meteo/book/BioMechan.htm
  2. Smith PK, Hamill J. The effect of punching glove type and skill level on momentum transfer. 1986, J. Hum. Mov. Stud. vol. 12, pp. 153-161.
  3. Walilko T.J., Viano D.C. and Bir C.A. Biomechanics of the head for Olympic boxer punches to the face. 2005, Br J Sports Med. vol. 39, pp. 710-719
  4. Holbourn A.H.S. Mechanics of head injury. 1943, Lancet. vol. 2, pp. 438-441.
  5. Ommaya A.K., Goldsmith W., Thibault L. Biomechanics and neuropathology of adult and pediatric head injury. 2002, Br J Neurosurg. vol.16, No. 3, pp. 220–242.

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