Today we will tell you in detail about what the dynamometer measures, and what varieties of this device exist. But before answering these and other questions, it is necessary to understand what the term "dynamometry" means. As you know, this word was formed from two Greek words: metron, that is, measure, and dynamis, strength.
It should be noted that this unit of measurement is especially often used in anthropometry, anthropology, neuropathology, during professional selection, the study of military contingents, fatigue, and so on.
What does a dynamometer measure?
From the foregoing, we can safely conclude that a dynamometer is a special device with which absolutely anyone can easily and quickly measure their own muscle strength.
By the way, the readings of such a device vary significantly depending on the duration and difficulty of professional work. In the event that this method allows you to obtain certain results in their graphical form, then it is called dynamography.
Currently, the presented device has many different models. The most common among them is a medical manual dynamometer, which is designed to measure the muscle strength of the hand. It is not for nothing that such a device is called medical, as it is often used in hospitals and clinics, to equip a medical room in sanatoriums, sports facilities and schools.
However, the answer to the question of what the dynamometer measures is not only the muscle strength of the hand. After all, there are such varieties of this device, which are often used for a similar measurement of the strength of the muscles of the legs and torso, characterizing the degree of physical development of a person.
Medical dynamometer: appearance and calculations
With the help of such a hand-held apparatus, a physician can easily and quickly determine the strength of the muscles of the patient's hand. During this procedure, two measurements are alternately taken on each arm, and then the best result is recorded. Outwardly, the presented device resembles a carpal expander. However, it looks a little different, with a sensor and a measuring board. In addition, the dynamometer is not intended for training cyclic work, but for a single compression with the maximum possible force for a person. If such a procedure is carried out exclusively for medical purposes, then the hospital employee is obliged to record the results in a special control log.
To obtain more objective indicators, subtract the relative magnitude of muscle strength. After all, its growth during training is quite closely related to the growth of muscle mass and body weight of the athlete. For example, in order for you to be able to independently determine the relative magnitude of the strength of your own hands, you need those readings that were obtained in kilograms from a hand-held medical dynamometer, multiplied by a hundred, and then divided by the person's body weight. So, for previously untrained men, this index will be 60-70, and for women - 45-50%.
Definition of backbone strength
By calculating the power of the hands, you can check the results in such a basic exercise as a deadlift. It is in this movement that all the power qualities of a person will be visible. This is due to the fact that with such an exercise, the athlete uses all the major muscles of the body.
To carry out such a measurement, it is necessary to use a special device that looks very similar to a conventional foot expander. It consists of a hand grip and a footrest. However, instead of springs, this device has a cable with a kind of measuring device in the middle.
The subject's task is to pull the handles towards themselves with the maximum possible force. In order to determine the required values, it is necessary to calculate the relative value of the deadlift in the same way as in the case of a hand-held medical device. Its results can be interpreted as follows:
If in the process of training the athlete's relative strength indicators significantly increase, then this indicates a significant increase in muscle strength and, accordingly, a percentage increase in the content of the muscle mass itself.
Factors that, one way or another, affect strength indicators
In the process of assessing the strength of the muscles for self-control, do not forget that it directly depends on such individual factors as:
In addition, indicators of muscle strength can vary significantly throughout the day. For example, the smallest value is observed in the morning and evening, and the largest - in the midst of the day, that is, in the middle.
It is also worth noting that a significant decrease in muscle strength in an athlete or an ordinary person is often noted during:
Among other things, the values on the dynamometer can be lowered in the elderly, as well as in those who are over 40-50 years old. A similar situation is often observed in men or women who rarely engage in physical culture, including regular gymnastics, walking, and so on.
Why do you need to know strength indicators?
Not everyone knows how and what a dynamometer measures. However, such a medical device helps quite well for those who regularly play sports. After all, systematic introspection allows a person to be creative about their daily workouts and a healthy lifestyle in general. Knowing the indicators of his own muscle strength, an athlete is able to effectively and rationally use physical culture to strengthen immunity and maintain health, as well as to improve performance and even professional growth.
Magic you can touch
The main human problem is internal dialogue . The most important organ in a person is the brain, the main part of the brain is the corrector, it controls and coordinates the work of the entire brain and its departments. All human control is carried out through the corrector. Put your palm on your forehead, everything that is 3-5 cm under it is a corrector.
A magician needs to control his brain. To do this, you need to learn how to cool the corrector. You must be able to completely relax and master the techniques of self-hypnosis, all magical practices imply that you know how. In the process of relaxation, one must imagine that the temperature of the corrector is lower than the temperature of the main mass of the brain. This will lead to vasoconstriction of the corrector, which is required to begin with. After that, it will seem to you that you are a little dumb (it is difficult to describe this state in another way), and you will also notice that there are fewer thoughts and, most importantly, emotions in your head. This exercise must be done every day. The first few days when performing the technique, you need to set a timer for about 10-15 minutes. in the beginning one cannot stay in this state for a long time.
The main two tasks in overcoming the internal dialogue: the first is not to return to playing previous actions in my head (but if I did that, otherwise everything would be different), the second task is not to pronounce the words at the level of the throat (neither tongue and ligaments should not work if we do not speak out loud).
All the main problems of a person arise because of his complexes; when carrying out the technique, you will have less and less of them.
The next task is to learn the first light impact on other people (hereinafter, for simplicity of presentation, “objects”). As I said, the main problems of objects are their complexes. Consequently, it is necessary to influence the object through its complexes (with time, you can learn to find them, but this is not necessary at the beginning).
The first most simple exercise: you need to learn how to heat / cool your hand. Relax, imagine or feel that the hand is not yours, that it lives its own life separate from you, then imagine that the brush becomes hot/cold and you will feel that it is getting hotter/colder. Don’t worry if you don’t succeed right away, the main thing is to practice.
I will give an example of how I did it at the beginning of my journey. I sat in a chair, relaxed (not entered into a trance, but just completely relaxed). After that, I put (or laid) my hand on the arm of the chair and looked at it, then I imagined that the hand was not mine at the moment, that it seemed to be living a life separate from me (it might seem that it had become cold).
You have to let go of your hand. It is necessary to give the brain a command that this part of the hand is not controlled by it, to inspire the brain that there are no nerves between it and the hand. And then try to move the fingers on that hand, it shouldn't work. After you need to imagine that the hand (palm) is heated, and you will feel how it heats up.
Then you need to learn to identify your hand with any (closely sized +/- a little) part of the body of the object, you need to get rid of your hand, then feel that your hand and part of the body of the object are the same (single whole), then start heating / cooling the brush hands, respectively, part of the body of the object will also begin to heat up / cool down, and this is what we need.
(All the examples I give are usually related to the impact on the opposite sex, this is due to the fact that at the beginning of training it is the easiest and the result is visible almost immediately. In principle, you can start with the treatment of people, while heating or cooling the diseased organs. )
It is necessary to attract the attention of the object. The sexual plan is the simplest, it is better when the object and the operator are of different sexes, this is due to the peculiarity of the brain. You identify the hand with the sexual organs (p/o) of the object, heat the hand, the blood flow to the p/o of the object begins to increase. Consequently, the object begins to experience excitement, but the most interesting thing is that the object is thinking about you at this moment (maybe even subconsciously). You can also slow down the operation of the object for some time by cooling the corrector for it, but this cannot be done often (preferably 1-2 times in general), otherwise it will not succumb to your influence later.
If you need your (a) boss (ca) to treat you positively, you need to influence (on the p / o) only in her (his) presence or look at you. In the process of performing the technique, boundaries (distances, walls) do not play a role. You can process the object even on the opposite side of the earth.
The second important topic is sensations (feelings). In order to get to it, you need to learn the concept absolute zero (a / n). We have learned not to think, the next step is to learn not to feel. In principle, this is almost the same thing: we calmed the thoughts, and now we need to calm the feelings.
You need to relax and feel that the whole body is neutral in relation to the environment and to you. Every part of your body lives a life separate from you, just like with a hand. Absolute zero is a mixture of not-thinking + not-feeling. You can not stay in this state for a long time. it is a drug for the brain, and at the beginning of training, a / n can drag out so that further training is no longer necessary. Having learned a / n, you will learn to completely control your body at the level of feelings, and eventually the whole body.
The next stage is the imposition of feelings. It is necessary to enter with the state a/n, then you need to remember any state (love, hate, joy, grief, attraction, etc.) and apply this feeling to a/n.
You see the object, in the a/n state enter it (ie, you associate your body and your feelings with the body and feeling of the object). Now everything that he feels, you feel (your body becomes, as it were, the body of an object). If now you remember some feeling and impose on the feelings of the object (as if on yourself), then after leaving the object, what you imposed will remain on the object. You can change your feelings, but the object cannot.
In force magic, when performing any kind of influence, only contact with force (hereinafter c / s) is used. There are no rituals, dances and dances in it. She cannot earn money, since the patient will not see any of your usual actions on your part. All techniques are performed directly by the influence of the MAG - the patient. All techniques are also very simple and seem implausible, but try it and you will understand that it all works.
Relax, get rid of thoughts and emotions. Try using the technique of self-hypnosis. In the process of self-hypnosis, imagine that some kind of black cloud envelops you (everyone has it differently, viscous, windy, a feeling of black emptiness, etc.), all thoughts gather into a small ball, it becomes smaller and smaller until it disappears completely and in its place something incomprehensible suddenly appears, some kind of feeling in the back of the head. At first it looks like a small ball that seems to pulsate and buzz with a frequency of 40-50 hertz (again, each in its own way), then it starts to grow and grow, the pulsation and hum gradually captures the whole body. Sit for a while in this state (1-2-3-.. minutes), then do everything in reverse order and exit this state. Over time, it will be enough for you to want, and you will already be able to k / s.
You have met power. The next step is how to accumulate power. Enter the state of ks, feel that you are in some kind of black tunnel (again, everyone has their own, just a tunnel, infinity around, etc.) and just being in it. While you are there, the power is gradually accumulated.
In principle, a black cloud and a tunnel are about the same thing. The difference is that in the cloud you are static, but in the tunnel you can move.
Enter the c / s state, then into the tunnel. Now imagine that you are transported to a certain room, it looks like a starry sky, stars from all sides: from below and from above. Now set a goal where you would like to go (get a feel for the area, house, etc.). You will feel how a certain force will carry you in the direction of one of the stars around, it will begin to approach and in the end, you will be thrown where you wanted. You can just walk around the worlds, approaching any of the stars, and see what is there. Also there you can find a teacher who will teach you.
Enter the state of c / s, imagine in front of you a person you don’t like. It should be in the form of a white glow on a black background. Now make it turn black and fade into the background. All damage has been done.
Inducing damage using the Voodoo method
Enter the state of c / s, imagine a person you don’t like in the form of a figure. You need to fully understand this person. Then imagine how you stick needles into it. Of course, it will not be like in the movies, but the result is excellent.
Place a person in front of you, enter the state of c / s, imagine that there is a fireball around the person (like a bubble). Talk to the fire so that it takes everything down.
Magic is one, there is no separation of magic by color. If the magician knows how to cure, he knows how to kill. All magical techniques work for both good and evil. It all depends on the magician and circumstances. There are three main postulates of magic - knowledge and possession of power, a corridor for movement and search, rhythms. All of them are given by the master (teacher) in an easy to understand form, in the future the student develops himself. Also one of the problems of magic is direction. If you try to develop in all directions at once, without a central path, then you will be overtaken and overtaken, and all specific techniques will be performed in the ratio 1/number of directions. And if there is one central direction, then 1/1 is central, 1/2 is the rest. Each magician is looking for his own central path, so some magicians are united in groups. Everyone in the group has their own direction and their own style of work. Also, the group should have a formal leader who tries to keep the group together and tries to look for the direction of the group. It is desirable that the group has an equal sex ratio. The main problem of the group is local wars among themselves and global wars with others. Local wars have a beneficial effect on the composition of the group, because. they allow you to keep yourself in shape outside of your direction, global ones have a bad effect on the surrounding population. The main goal of magic is self-development, a secondary goal is life in the world around. Magic is directly related to psychology, and some techniques overlap. The first thing the master teaches the student is the feeling of power and possession of the corridor. In the future, the student himself learns to accumulate power and use it. By finding the central direction and following it, the student can find knowledge that is unknown to his teacher.
Synopsis of a physics lesson Grade 7: Forces in mechanics
Type of occupation: Lesson of generalization and systematization of knowledge
Forms of work: individual, frontal.
Teaching methods: verbal, visual, practical, problematic.
— Media product: Wednesday - Microsoft Office Power Point. (visual presentation training material (Appendix 4).
— experimental equipment, which allows to measure any mechanical force.
1. Organizational moment. Setting goals and objectives of the lesson.
2. Actualization, systematization of basic knowledge.
a) Comprehensive knowledge testing.
b) Independent work, mutual check, self-check
3. Lesson results, conclusion.
The teacher presents the students with an expert commission (these are two students who answered all the questions of the topic the day before the seminar), explains why the children were given sheets with a table (Appendix 2), formulates the concept of types of forces in nature and leads students to formulate goals and objectives lessons. (Slide 2)
Students answer questions of a theoretical nature. (Slide 3)
1. Define strength.
(Force is a quantitative measure of the action of one body on another, as a result of which acceleration is imparted to the body.)
(Gravity is the force with which the Earth acts on any body located near its surface. Gravity is always directed towards the center of the Earth, is determined by the formula F \u003d mg, where g is the free fall acceleration, equal to 9.8 m / s 2 .)
3. Under what condition do elastic forces arise?
(The forces of elasticity arise when the body is deformed. In this case, they are always directed against the deformation.)
4. Define body weight.
(Body weight is the elastic force resulting from the deformation of the body and directed to the support or suspension from this body.)
5. When do friction forces occur?
(Friction forces arise from the interaction of two bodies in contact.)
6. How can the friction force be reduced or increased and in what situations?
(Reduce the force of friction by lubricating or polishing between the rubbing parts of the engine; increase the force of friction with the help of branches and sand when the car slips.)
Students use experimental equipment to solve problems. (slide 4)
1. How to measure gravity?
2. How to measure the spring force?
Students explain the solution of pre-prepared problems. (Slide 5.6)
1. Why do raindrops, snow grains fall on the ground?
2. In a vessel with water there are two bars of the same mass - wooden and copper. Which of the bars is affected by the greatest force of gravity?
3. Does a weight hanging on a thread have weight? What will be the weight of the kettlebell if the string is cut?
4. Does gravity act on a swift flying in the air?
5. Will the skydiver be in a state of weightlessness during the jump?
6. Why are notches made on the jaws of a vise and pliers?
7. Why is a relief pattern made on car tires?
To check the assimilation of the material, independent work is carried out in the form of testing in two versions for 15 minutes. (Appendix 3)
At this stage, the floor is presented to the expert committee. The guys evaluate the answers of other students, make comments, give recommendations for the future. The children independently decide whether the objectives of the lesson have been achieved. In the final speech, the teacher expresses his opinion about the lesson, emphasizes that the systematization of knowledge on this topic is necessary to study the following sections of physics.
Questions to prepare for the lesson.
1. Define strength.
2. Define gravity. What is the free fall acceleration?
3. How to measure gravity?
4. Under what condition do elastic forces appear?
5. How to measure the spring force?
6. When do friction forces arise?
7. How can the friction force be reduced or increased and in what situations?
8. What determines the modulus and direction of the friction force?
9. Can the force of friction increase the speed of a body?
10. How to measure the force of sliding friction?
1. What is called the state of weightlessness?
2. Will the skydiver be in a state of weightlessness during the jump?
3. Explain why the use of springs reduces vehicle shaking.
4. Why are notches made on the jaws of a vise and pliers?
5. Why is a relief pattern made on car tires?
6. What force imparts acceleration to a car or locomotive?
Table for systematizing knowledge on the topic "Forces in mechanics"
Prosthetic limbs for amputation
Hand prostheses - bionic hand
Hand prostheses are intended for patients with stumps of the upper extremities at the level of the hand after unilateral or bilateral amputation. There are such prostheses, both cosmetic and working (functional).
In recent years, great attention has been paid to the creation of functional hand prostheses, and significant progress has already been made in this direction. There are really serious and very encouraging results. First, Touch Bionics, headquartered in Scotland, launched stationary and fully removable electronic robotic prostheses for hands and individual fingers on the world market. Such biomechanical prosthetic systems ProDigits and i-LIMB have unified interchangeable units, including finger phalanges, are powered by batteries and programmed via Bluetooth interface.
Then the British company BeBionic created the bionic hand, the most advanced prosthetic hand in existence today. This invention is based on the use of the so-called myoelectric control system, supplemented by the possibility of fine adjustment of the device by the user.
This means that a person himself can set the grip strength, as well as the reaction of the prosthesis to certain objects, the response speed of the device and a number of other parameters, and then transmit this information wirelessly to his electronic hand. The myoelectric system, in turn, by reading muscle impulses in the intact part of the limb, allows the user to easily dispose of the bionic hand as if it were his own hand. In other words, such a prosthesis is controlled by interpreting the signals that occur during the contraction of the muscles of the hand, and a person has the opportunity to independently adjust the parameters of the cybernetic prosthesis, for example, program the squeezing force of artificial fingers in order to crush a tin can without any problems and not crush it. fragile egg.
By the way, previous developments in this area have shown only the possibility of squeezing and unclenching the palm. The invention of BeBionic is the world's first bionic hand capable of performing rotational articulation. In addition, here communication with the control computer is implemented without wires, unlike the vast majority of previous schemes equipped with a USB interface.
Outside, the device is covered with silicone "skin", which gives it an aesthetic appearance. Thanks to this, the bionic hand is not much different from a normal human hand. Now, for the most inconspicuous integration of the prosthesis into the user's limb, the developer company offers nineteen options for external shades.
Thus, the plot from the notorious Star Wars, where Luke Skywalker's hand, cut off by Darth Vader, is replaced with a fully functional cyber prosthesis, is gradually becoming a reality. There remains, perhaps, one unresolved issue at the present time - this is the very high cost of the bionic brush.
Limb prosthetics in Moscow
The Rehabilitation and Orthopedic Center in Moscow has been engaged in lower limb prosthetics for the past ten years. The ROC manufactures a wide range of modern modular prostheses using high-tech modules from the Icelandic company Ossur and the German company Otto Bock. In addition, the specialists of the center for the manufacture of prostheses in a budget configuration use the well-proven modules of the Russian company Metiz. More
Intelligent prosthetic leg C-leg
The microprocessor-controlled C-Leg lower limb prosthesis uses a pneumatic actuator to provide the wearer with a sensation similar to that of walking on both legs. The pressure sensor (load cell) measures the load on the prosthesis fifty times per second, and due to this, the process of bending the artificial knee and ankle is properly carried out. According to users, walking with a C-Leg is much easier than moving around on conventional “non-intelligent” prostheses: you can go down stairs without problems, whereas you had to avoid it before, etc. More
Biocybernetic neural interfaces – BrainGate2
Thanks to this device, for the first time in the history of mankind, a completely paralyzed person was able to drink coffee from a bottle on his own, using the electrical activity of his brain and controlling a robotic arm resembling a hand with the power of his thoughts. For this, a 58-year-old patient named Kate had a special neurochip implanted in the motor area of the cerebral cortex, consisting of ninety-six gold contacts and allowing the conversion of neuron signals into commands for an artificial hand. More
Dynamometers measure carpal muscle tone in children and adults in order to determine the overall performance and strength of a person, as well as to monitor the dynamics of the recovery process after injuries, in the process of preparing athletes, for conducting dynamometry during medical examination of the population. Modern instruments show force in decanewtons (daN). This unit is analogous to the kilogram-force (kgf).
The principle of operation of the dynamometer
Dynamometer operation is based on the law of physics, according to which the deformation that occurs in a spring or other elastic body is directly proportional to the force (stress) applied to the body. This law bears the name of Hooke, an English scientist who lived in the 17th century.
Hooke's law says that in response to the deformation of a body, a force appears, seeking to return the initial shape and original size of this body. It's called resilience.
The simplest dynamometer is a combination of two devices - power and reference!
The force applied to the device is the deformation of its power link. By means of an electrical signal (or mechanical), the deformation is transmitted to the reference link, which can be digital or analog.
The unit of measurement of the instrument is Newton (N), the international unit of force.
If the scales show the mass of the human body, then according to the readings of the dynamometer, one can judge the force that the person applies, deforming the instrument spring.
Modern device for dynamometer- This is a control and measuring device that is widely used in medicine to measure the tension or compression force in people, measured in newtons, as well as the moment of force in kilogram-forces.
The design of the device allows a person to independently measure their muscle strength!
The main types of dynamometers in medicine
The first dynamometric devices, which were spring mechanisms, were created in the middle of the 18th century. The spring in them, under the influence of the load, was stretched to a certain length. The divisions on the scale, showing the elongation of the spring, corresponded to the mass of the load. Some time later, a dial device with a round spring of a closed circuit was invented. After devices with tension mechanisms, designs that work under pressure were invented.
Today there are dynamometers of the following types:
Devices with a mechanical principle of operation are:
There are models of dynamometric devices in which two types of power devices are involved at once!
In medical practice, the following types of devices are most often used:
- mechanical spring . The force in it is transmitted to a compressing or stretching spring. The value of the elastic force in this case is strictly proportional to the magnitude of the deforming effect. The spring principle of operation is applied in the simplest steelyard.
- Mechanical lever. The deforming force is transmitted in this device by means of a lever. Dynamometer readings record the amount of deformation. The operation of a car torque wrench is based on this algorithm of action. The reading accuracy of both mechanical devices depends on the ambient temperature.
- Hydraulic. Under the influence of the force measured by the device, the liquid is squeezed out of the hydraulic cylinder. Then it passes through the tube and enters the recording sensor, which registers its exact amount. This device is more accurate than its mechanical counterparts, but much more difficult to manufacture. The reliability of the readings here directly depends on the accuracy of the dosing of the liquid and on the quality of the tightness.
- Electronic. In it, the deforming force entering the sensor is converted into an electrical signal. In addition, the device has another sensor. It amplifies the signal coming to the first sensor and fixes it in the device's memory.
- The second, free hand must be relaxed and lowered down.
- Then it must be taken to the side and placed perpendicular to the body.
- The hand with the device should be extended forward.
- Squeeze the dynamometer with a brush as strongly as possible on command.
In electronic designs, types of inductive, piezoelectric and other sensors are used. In the process of deformation of the sensor, the resistance increases - as a result, the currents change. As a result, the force of pressure on the sensor is directly proportional to the strength of the electrical signal transmitted by the device.
An electric dynamometer is a high-precision, small in size and light in weight device!
What is the difference between a hand or hand dynamometer and a deadweight dynamometer?
In medicine, dynamometric devices are used to determine the strength, assess the performance and endurance of the human body. With the help of these simple devices, one can make a fairly accurate conclusion about the state of human muscles.
For medical purposes, mainly hand dynamometers and stand models of devices are used!
Option hand dynamometer determines the muscle strength of the fingers of a person squeezing it with his hand. Hence the second name - carpal. This device is widely used by physiotherapists to evaluate the dynamics of the restoration of the patient's muscle strength after an injury. Wrist dynamometers are widely used in forwarding and transport companies when testing newly hired employees. They are also used in law enforcement agencies, the Ministry of Emergency Situations and the armed forces, in professional sports organizations and fitness clubs.
Today, manual devices of mechanical and electronic modifications are produced. The accuracy of measurements with their help depends on the observance of certain rules by a person during measurements.
These rules are very simple and are as follows:
According to this algorithm, the strength of each hand is measured in turn, several times in a row.
From the results obtained for each hand, the one that is better is selected!
With an increase in muscle mass during training, the indicators obtained using a dynamometer improve.
Accurate absolute indicators rather difficult to obtain, as they are influenced by many subjective factors. Therefore, as a rule, the magnitude of the relative strength of the hands is taken into account. To calculate it, the force measured by the dynamometer in kilograms is multiplied by one hundred, and then divided by the weight of the human body. For people who are not professionally involved in sports, the relative indicator is 45-50 units for women and 60-70 units for men.
With the help of deadlift dynamometers, you can test for static strength and endurance all the muscles that bend and unbend the human body!
The camp device is similar in appearance to a foot expander. Its components are a handle, a footrest, a cable, a measuring device equipped with a sensor and a reading device.
To measure muscle strength, a person needs:
- Stand with both feet on the footrest of the device.
- Tilt the body forward, bending at the waist.
- Grasp the handle of the dynamometer with both hands.
- Do not bend your knees while doing this.
- Then the handle of the device must be pulled up towards you with all your might.
- He is ill with some disease or is experiencing a temporary malaise.
- The person is in a state of depression or stress.
- For a number of reasons, the diet habitual for his body and the daily routine have gone astray.
- What is the direction of the static friction force? What does the force of friction depend on? Why does friction force occur? Give examples of static friction, which helps to set the body in motion. Give examples of static friction that interferes with movement. Where is the static friction force directed if the load is lifted by transport? Why does sliding friction decrease with decreasing temperature? Under what conditions does a dynamometer measure the force of friction? Why is a deep tread pattern made on the wheels of tractors and cars?
- What is the direction of the static friction force?
- What does the force of friction depend on?
- Why does friction force occur?
- Give examples of static friction, which helps to set the body in motion.
- Give examples of static friction that interferes with movement.
- Where is the static friction force directed if the load is lifted by transport?
- Why does sliding friction decrease with decreasing temperature?
- Under what conditions does a dynamometer measure the force of friction?
- Why is a deep tread pattern made on the wheels of tractors and cars?
- Why does a swimmer, jumping from the starting block, stretch his arms forward?
- Which bullet flies further, round or conical?
- Why do small fish, moving over long distances, stray into flocks in the form of a drop?
- Do orbital stations need to be streamlined?
Calculation principle relative indicators for standing devices is the same as for manual ones. But the indices are much higher. With an index of up to 170 units, the backbone strength is rated as low. Indicators from 170 to 200 units indicate strength below average values. The average is the strength of the muscles that straighten the body with index values from two hundred to two hundred and thirty. An index from 230 to 260 indicates values above the average. And more than two hundred and sixty are indicators of a high trunk extensor force.
Why do you need to know strength indicators?
The strength of a person's muscles is influenced by his gender and age, body weight and level of fatigue. The strength indicator largely depends on the time of day and the type of muscle training.
It is noted that in the middle of the day, as a rule, the maximum value of this indicator is fixed. And in the morning and in the evening - the minimum.
At the same time, the normal muscle strength of a particular person may be weakened due to the fact that:
Often, these indicators are lowered in the elderly and in people who do not maintain themselves in proper physical shape.
Doctors prescribe to patients the measurement of muscle strength on a dynamometer to monitor the physical development of both children and adolescents, and adults.
When carrying out measurements, it is necessary to ensure that in the initial position the arrow of the device is at zero!
After the measurement, the readings must be recorded. This will help doctors further assess the change in the state of human health over a certain period of time.
For those with low levels of muscle strength, doctors recommend engaging in an acceptable sport. After all, physical exercises are done not only to build biceps. First of all, they strengthen the body's immunity, increase its efficiency.
Overview of popular models and prices for medical dynamometers
In Russia, several varieties of medical dynamometric devices are produced. Among them there are mechanical and electronic models. For adults and children, stand and hand devices of different price categories are produced.
Hand dynamometer DK-25, DK-50, DK-100, DK-140
The listed models belong to the category of spring mechanical devices. They are designed to measure muscle strength in people of different ages and health conditions. Devices for dynamometry are needed in polyclinics and dispensaries, in sanatorium and health-improving and clinical institutions, in sections of various sports.
The principle of operation, the shape and size of these models differ little from each other. The main difference is in the measurement range.
The numbers included in the name of the device indicate the upper limit of the range!
In particular, DK-25 is a hand dynamometer that allows measuring force up to a maximum of 25 decanewtons. The DK-140 device has an upper measurement limit of 140 decanewtons.
The cost of manual spring models ranges from 3100 to 3900 rubles.
Dynamometer DMER-120, DMER-30
These models are hand-held electronic devices manufactured to measure the hand muscle strength of patients. They are used in clinics, hospitals, rehabilitation centers, school medical offices. They are also used in professional and amateur sports and in physiological practice.
Device DMER-120 issued for adults. When compressing the body of the dynamometer with a brush, the applied muscle force is converted into an electrical signal of a certain frequency. The obtained readings are processed in a digital microprocessor. The device is equipped with a liquid crystal display with an indicator, which displays the final result. It can be used to measure from 2 to 120 daN.
There is a version of this model with an indicator placed outside the device!
The price of the model is about four thousand rubles. The version with a remote indicator costs 500 rubles more. The design has an autonomous power supply system from battery cells.
DMER-30- This is a children's dynamometer. They measure the strength of the muscles of the hands in older and middle-aged children.
It is convenient for a child to hold this device in his hand, as it has a small body!
In addition, the device is very light - it weighs only 90 grams. The device can operate in two modes. The normal mode after measurements must be turned off manually. In economical
mode provides for automatic self-shutdown of the device one minute after the measurement. The maximum measurement limit of this instrument is 30 daN. The cost of this model is 3400-3600 rubles.
Stationary dynamometer DS-200
This torque gauge has a measuring range of 20 to 200 daN. The body of the bench force meter is made of silumin material and varnished. The spring part is made of nickel-plated steel.
The device determines the static endurance and strength of the flexor and extensor muscles of the human body!
The device is equipped with a special mirror, thanks to which you can see the scale readings during the application of muscle effort.
The deadweight dynamometer is used in physical therapy rooms, orthopedic and neurological clinics, research laboratories and sports.
The price of the backbone dynamometric device is in the range of 9950-12250 rubles.
Physics presentation on the topic "The force of friction"
Ensure the assimilation of material on the topic " Friction force».
Formation of scientific-materialistic outlook.
Friction is the force that arises when one body moves along the surface of another, applied to the moving body and directed against the movement.
static friction force prevents the relative displacement of the contacting bodies. It grows along with the force that strives to move the body from its place.
The force arising from the movement of one body on the surface of another and directed in the direction opposite to the movement is called the force of sliding friction.
Development content
Completed by: physics teacher
MBOU secondary school №76 Penza
Ensure the assimilation of material on the topic
Involve students in the learning process, develop interest in physics with the involvement of local material.
Formation of a scientific-materialistic worldview
The force arising from the movement of one body on the surface of another, applied to the moving body and directed against the movement.
The static friction force prevents the relative displacement of the contacting bodies. It grows along with the force that strives to move the body from its place.
If a body rolls on the surface of another body, then the friction that occurs at the point of contact is called rolling friction.
SLIDING FRICTION ROLLING FRICTION » width=»640″
Comparison of sliding friction force and rolling friction force
For equal loads, the rolling friction force is much less than the sliding friction force.
STANDING FRICTION SLIDING FRICTION ROLLING FRICTION
Group #1: Study of the dependence of the friction force on the area of rubbing surfaces.
- Move the block with a large edge evenly using a dynamometer along the ruler of the tribometer.
Measure the force of friction.
-Put the bar on the ruler with the smaller edge, repeat the experiment of uniform movement of the bar and again measure the friction force.
Based on the values of the friction force, make a conclusion about the dependence/independence of the area of the rubbing surfaces.
Group #2: Study of the dependence of friction force on pressure.
Group #3: Comparison of sliding friction force and rolling friction force .
- Move the dynamometer with the bar attached to it evenly along the board.
Measure the force of friction.
- Place a weight of 100 g on the bar, pressing the bar to the table, measure the friction force again.
- Add another 100 g weight.
Draw a conclusion about the dependence of friction force on pressure.
- Put the bar on two round pencils, measure again
Compare the force of sliding friction and the force of rolling friction.
The friction force can be measured with a dynamometer.
Two forces act on the block in the horizontal direction. One force is the elastic force of the dynamometer spring, directed in the direction of motion. The second force is the friction force directed against the motion. Since the block moves uniformly, this means that the resultant of these two forces is zero.
The force of friction depends on the weight of the body.
Force must be applied to move a body off the support. This force balances the force of friction. The static friction force can reach large values in magnitude. When a rubber bar moves on concrete, it is 0.6–0.7 part of the body weight.
The force arising from the movement of one body on the surface of another, applied to the moving body and directed against the movement.
Applied to the contact surface of the bodies.
Directed along the contact surface of the bodies, against the movement .
The body is uniformly moved using a horizontally located dynamometer.
Reasons for the emergence of strength
Roughness of surfaces of contacting bodies.
Mutual attraction of molecules of polished surfaces .
increase: increase in load, use of special materials
decrease: grinding, lubrication, bearing
For plants such as burdock, friction helps to spread the seeds, which have spines with small hooks at the ends. These spines are hooked on the fur of animals and move along with them. Seeds of peas, nuts, due to their spherical shape and low rolling friction, move easily on their own.
The skin of the dolphin has a special damping effect that allows it to dampen turbulence. The front of the dolphin's body flows laminarly, while behind the dorsal fin the boundary layer becomes turbulent.
Thus, the "softness" or "waviness" of dolphins' skin helps them greatly reduce friction when sliding through the water.
Friction of human joints
In humans, the bones forming the joint do not touch each other; they are covered with articular cartilage, which acts as a buffer between bone surfaces.
The elasticity of blood vessels arises due to a special substance - elastane. The special laminar regime of blood flow also contributes to the reduction of friction losses.
Pump up your arms at home, or for men - mass, for women - relief!
How to pump up your arms at home without dumbbells? This question worries beginners and experienced athletes, regardless of gender.
For men, beautiful biceps are an indicator of strength and aesthetics.
It is important for women to keep the top taut so that every outfit on such a body looks perfect.
Both those and others will be helped to realize the plan by special exercises for these muscle groups.
But what if you can’t start training in a fitness club for one reason or another?
Believe me, nothing is impossible for a person with a thirst for action. You can find the rest of the details in this article.
How to pump up your arms at home? Basic rules for achieving quick results
Before you start training, remember that the arms are not only the “banks” of the biceps.
This is a thoughtful combination of joints, muscles, tendons, which is a complex biological mechanism.
Therefore, pumping this part of the body, it is important to understand the general principles of their work.
During your workouts, be sure to consider which muscle group the load is being applied to.
Think of your own hands as an amalgamation of these areas:
- Biceps
- Triceps
- Forearm
- Deltoid muscle (but it's more like shoulders)
- Train hard and often. Do not listen to those who say that 2 times a week is enough. Not enough! Do you think Iron Arnie (Schwarzenegger) trained like this at the peak of his form? No. Dwayne "The Rock" Johnson? No. Someone will say: “I don’t need such a level.” But you are counting on a good result! Their example proves once again that beautiful hands cannot be pumped up under any conditions without difficulty.
- Follow the routine. Muscles grow in sleep, not during exercise. If you sleep well, then you recover faster. Eat right, not forgetting about the protein - the muscles grow, and the fat melts.
- Choose your projectile weight wisely. If the chosen program is aimed at the load of the "ladder" type for a decrease, when the number of repetitions is 12, 10, 8, 6, 4, the weight of the dumbbells should not be higher than 60-70% of your maximum, which is determined in advance. If there are fewer approaches, take such a weight that you can lift it about 8-10 times, observing the correct technique for each movement.
- Surprise your body by constantly changing your training program and load. People get used to everything, even stress.
- Do not forget to warm up so as not to get injured, and therefore do not interrupt training. Drink water between sets and increase the weight by at least a kilogram or several times weekly. You are both a coach and a subordinate. Be hard on yourself, but listen to your body. How to quickly and safely pump up your hands at home? Educational thematic video will help you achieve your goal. Look a few before the first "start".
- Stand up straight and grab a dumbbell in your hands. At the bottom point, the palms look forward. Fully align your spine, pull your shoulder blades back. Positioning of the legs - no wider than the hips. Gently raise your arms, bending them at the elbows, and bring the weight to your chin. At the bottom point, fully straighten the upper limbs. It is very important here not to sway, because in this way you will remove any load from your hands. Keep your elbows close to you, this is a prerequisite for proper movement. Try this exercise with your back against a wall and you will feel the difference. It has become more difficult, but such an isolated load will have a beneficial effect on the development of beautiful biceps.
- How can you pump up your arms at home without dumbbells for a girl? Take a bottle of sand or any shells of the same weight. In some cases, even a backpack full of books will do. Perhaps somewhere on the balcony lay grandfather's old weight.
- Take a dumbbell in each hand and place them along the legs (closed palms pointing at the body). Perform alternate bending to shoulder level. But by doing combined (simultaneous) curls right away, you will save time and load the biceps much better. A little secret: try to bring your elbow slightly forward and at the same time not sway.
- Sit on the edge of the bed and pick up any weights. Still not sure how to build arms at home for a guy or girl without dumbbells? Use any suitable equipment. Even a cobblestone in a bag is quite suitable, show your imagination. Bend your arms and in parallel, while moving at the top point, change your grip and turn your hands outward.
- Palms facing up (more tension on the biceps)
- The brushes are turned to the floor (the forearms are well tensed)
You can achieve beautiful hands, even doing at home
How to pump up hands at home for a girl? Stretch longer!
Even when we "press", the insidious body seeks to reduce the load, compensating for this with swaying.
If you perform the ascent, and especially the descent of the projectile (return to the starting position) extremely slowly, then you yourself will feel how much more difficult it is to do the exercise and how rapidly its effectiveness increases.
Track yourself and feel at what point in the movement you feel the maximum tension. The amplitude is also important. The more it is, the better.
But if you are looking for an answer to the question of how to pump up your arms at home from scratch, that is, there is no experience, you should focus on the rhythm of breathing.
If a person suffocates while moving, it is allowed to use the mouth.
The main thing is that there is enough oxygen, and there is no delay in exhalation-inhalation during the difficult moments of the training.
Also keep in mind the following rules:
Try to combine proper nutrition and regular exercise for the fastest results.
Tip: You may wake up early in the morning and feel an incredible craving for… jelly. Do not deny yourself a small portion, because, perhaps, the body requires additional nourishment. 18 amino acids in its composition, or rather, in the composition of gelatin, have a beneficial effect on ligaments and tendons, strengthening them.
How to pump up your arms at home with dumbbells. Basic exercises for biceps
Perhaps you have a similar weight lying around on your balcony: its time has come
Tip: at the moment of movement, focus on the muscles and the tension in them. Be patient when a burning sensation appears, this is normal.
Compact assistant for the beauty of hands - expander
In this case, we are talking about a design with a spring (rubber) and handles.
How to pump up your arms at home without dumbbells and a horizontal bar - use an expander!
It can be used for a good workout of almost the entire body. To "pump" the area of interest to us, step on its middle and rhythmically raise your hands up to your shoulders.
Always choose a unit that will be noticeably hard to work with. Only in this way will you achieve the desired results.
Get an expander for home workouts
You can train using several grips:
During the set, it is important not to "cheat" with tension due to the mobility of the hands, but to keep your arms straight.
The next exercise is considered more difficult. Stand with one foot on the expander and bend the knee, the main emphasis is placed on the leg.
The other leg is straight. Tilt your torso and rest your hand on the side of the "non-leading" leg on the thigh.
Take your free hand with the expander back as far as you can. In fact, the part below the elbow works, and the joint itself is motionless.
Change sides when you feel tired.
Deltas are well worked out with the help of swings to the sides due to the opposition of the sports equipment.
Then raise your hands in front of you. Next, put your hands behind your head and lift your arms, bending them as much as possible.
The hands clenched in fists should lightly touch each other. This exercise is perfect for triceps.
Additionally, you can fasten the rubber to the doorknob, lunge forward and straighten your arms forward, as if pointing up.
Tip: The color of the expander speaks of its cushioning. The easiest way to use yellow, and the most difficult - red and blue.
If it is not possible to purchase expensive dumbbells, quite tolerable options can be purchased on used items sites.
Exercises for the "steel" triceps
Tip: it is most convenient to do the second exercise with small dumbbells, large weights cling to the head, so pay attention to increasing the number of repetitions.
We work out the forearms
This area is sometimes the most difficult to work out, so you will need additional equipment.
All this can be found in every home:
Connect all these components. Come to the table, we put a stool on it so that your hands lie on the surface at shoulder level.
With the help of brushes, we begin to wind the rope around the stick, pulling the load up. In the same way, we unwind it back.
Exercises with the usual Martens pharmacy bandage will also work great.
Get a Martens bandage and secure it in any way possible to the surface at chest level.
You can combine it with a rope and just press the door. Fasten it around the hands and pull the bandage back, directing your hands behind your head.
The result should be movements similar to the “hammer”.
A simple car cable will also come in handy. Having made two loops on it, you can do pull-ups using your own body weight.
At the same time, the hands move similarly to the previous exercise.
Holding the dumbbells in your hands, alternately pull the weight to the opposite part of the chest from it, each time fully straightening the limb.
The brush, in turn, moves along the body. This exercise perfectly pumps up the forearms, significantly increasing the strength of the grip.
Tip: buy a Martens bandage at your nearest pharmacy, it is sold everywhere.
(Codifier elements 1.10- 1.20; 1.27 - 1.28)
1.10
A) body acceleration
B) the magnitude of the deformation of bodies
Answer: 2
1.11
Answer: 3
1.12
1)12)23)34)4
Answer: 2
1.12
1)0 N
2)500 N
3)1000 N
4)2000 N
Answer: 2
1.13
1)F 1 \u003d F 2 3) F 1 2)F 1 >F 2 4)F 1 »F 2 Answer: 1
1.14
(B, VO). Two forces F,= 2N and F 2 = 3H are applied to one point of the body. The angle between the vectors F and F 2 is 90°. What is the modulus of the resultant of these forces? 1) 1H 2) H 3)5 N 4)13 N Answer: 2
1.15
1) The principle of conformity 2) The principle of superposition of forces 3) The principle of complementarity 4) The principle of relativity Answer: 4
1.16
1)02) 1 3) 2: 54) 5:
2
Answer: 2
1.17
1) 1 N3) 9 N 2) 6 N4) 12 N Answer: 1
1.17
Answer: 2
1.18
Answer: 4
1.19
1)0,1
2)0,2 3)0,25 4)0,5
Answer: 3
1.19
(P, K). What is the stopping distance of a 1000 kg car moving at a speed of 30 m/s on a horizontal road? The coefficient of sliding friction between the road and the tires of the car is 0.3 (g = 10 m/s 2). Answer: 150 m
1.20
Answer: 3
1.27
Answer: 3
1.28
Answer: 3
Task 1. Task 2 Task 3. 2. THEMATIC BLOCK "DYNAMICS"
(Codifier elements 1.10- 1.20; 1.27
- 1.28)
1.10
(B, VO). The student measures the strength of his hand with a spring force meter. In this case, the connection of the force c .. A) body acceleration B) the magnitude of the deformation of bodies 1) Only A 2) Only B 3) Both A and B 4) Neither A nor B 1.11
(B, VO). The resultant of all forces acting on the body is zero. What is the trajectory of this body? 1.12
(B, VO). On fig. 13A shows the direction of the body's velocity and acceleration at a given time. Which of the arrows (1 - 4) H and fig. 13B corresponds to the direction of the resultant of all forces acting on the body? 1)12)23)34)4
1.12
(P, IN). The speed module of a car weighing 500 kg changes in accordance with the graph shown in fig. 14. Determine the module of the resultant force at time t = 3 s 1)0 N 2)500 N 3)1000 N 4)2000 N 1.13
(B, VO). The moon and earth interact by gravitational forces. What is the ratio between the modules of forces F 1 , the action of the Earth on the Moon and F 2 of the action of the Moon on the Earth? 1)F 1 \u003d F 2 3) F 1 2)F 1 >F 2 4)F 1 »F 2 1.14
(B, VO). Two forces F 1 \u003d 2H and F 2 \u003d 3H are applied to one point of the body. The angle between the vectors F and F 2 is 90°. What is the modulus of the resultant of these forces? 1) 1Н2) √13 H 3)5Н4)13Н 1.15
(B, VO). What fundamental principle does Galileo justify in the following fragment of the book: “Close yourself with a friend in a spacious room under the deck of a large ship. While the ship is not moving, watch the fish in the aquarium swim indifferently in all directions, drops falling from the tap will fall into the substituted vessel "And you, throwing a thing to a friend in one direction, will not be forced to use a force greater than to throw it in the other direction. In jumping, you will cover the same distance in all directions. Observe well all this with an even the movement of the ship at any speed. You will not notice the slightest change in all these actions when the ship is moving evenly and when it is stationary; you will not be able to judge from any of them whether the ship is moving or standing still. "? 1) The principle of conformity 2) The principle of superposition of forces 3) The principle of complementarity 4) The principle of relativity 1.16
(B, VO). If the lever in Fig. 15 is in balance, then the ratio of the moments of forces F 1 and F 2 is ... 1)02) 1 3) 2: 54) 5:
2
1.17
(B, VO). Two forces act on the lever, the arms of which are equal to 0.1 m and 0.3 m. The force acting on the short arm is equal to ZN. What must be the force acting on the long arm in order for the lever to be in balance? 1) 1 N3) 9 N 2) 6 N4) 12 N 1.17
(P, IN). A homogeneous rod OA is attached to the wall with a hinge O and is kept in balance with the help of a thread AB. Which of the arrows correctly shows the direction of the force acting on the rod from the hinge side (Fig. 16)? 1.18
(B, VO). The spacecraft, after turning off the rocket engines, moves vertically upward, reaches the top of the trajectory, and then moves downward. On what part of the trajectory in the ship is the state of weightlessness observed? Air resistance is negligible. 1) Only during upward movement 2) Only during downward movement 3) Only at the moment of reaching the top point of the trajectory 4) During the entire flight with the engines not running. 1.19
(B, VO). On fig. 17 is a plot of the modulus of friction force F versus the modulus of normal pressure force N. Determine the coefficient of sliding friction. 1)0,1
2)0,2 3)0,25 4)0,5
1.19
(P, K). What is the stopping distance of a 1000 kg car moving at a speed of 30 m/s on a horizontal road? The coefficient of sliding friction between the road and the car tires is 0.3 (g = 10 m/s). 1.20
(B, VO). The student conducted experiments with two different springs, measuring the elastic forces at different deformations. The results of the experiments are given in table. 3. Hooke's law under the conditions of the experiments. 1) validated only for the first spring 2) only confirmed for the second spring 3) confirmed for both springs 4) not confirmed for any of the springs 1.27
(B, VO). A syringe draws water from a glass. Why does water rise with the piston? 1) Water molecules are attracted by piston molecules 2) The piston with its movement entrains water 3) When rising between the piston and the water, an airless space is formed, where water rushes under the pressure of the outside air 4) None of the explanations given is correct. 1.28
(B, VO). What is approximately equal to the Archimedean force acting on a body with a volume of 2 m 3, half immersed in a liquid with a density of 1000 kg / m 3? 1) 2000N 2) 5000 N 3) 10000 N 4) 20000 N Task 1. A load suspended from the ceiling moves in a circle in a horizontal plane spaced from the ceiling at a distance h = 2 m (conical pendulum). Find the circulation period T of the cargo. Task 2. At what speed will the passengers of a car passing over a convex bridge with a radius of curvature R = 40 m experience a state of weightlessness? Task 3. From the roof of a house with a height h 0 = 25 m vertically upwards a stone with a speed υ 0 \u003d 20 m / s. Determine the time and height of the ascent, the time of the entire flight and the speed of the stone when it falls to the Earth. Dynamics
Dynamics
1) 2) 3) 4)
1) α/2 2) α 3) 2 α 4) arctg(cos α)
Inertia. Newton's first law
Phone interaction. Force. The principle of superposition of forces.
Dynamics
A 1. The student measures the strength of his hand with a spring force meter. In this case, the power ability is used:
I. change the speed of bodies II. cause deformation
1) only I 2) only II 3) both I and II 4) neither I nor II
A 2. Three forces begin to act on a body at rest, shown in fig. Where will the body move?
1) 2) 3) 4)
A 3. What is the angle between the resultant vector of two identical forces and the OX axis, if one
of the forces is co-directed with this axis, and the second forms an angle with the OX axis?
1)
arctg(cos)α
α
/2 2)
α
3) 2
α
4)
Inertia. Newton's first law
A 5. The reference system is connected with the car. It can be considered inertial if the car
1) moves evenly along a straight section of the highway 2) accelerates along a straight section of the highway
3) moves evenly along a winding road 4) rolls uphill by inertia
A 6. The figure shows a graph of the change in the module of the speed of the rectilinear movement of the car with
over time in an inertial frame of reference. At what time intervals is the total force
acting on the car from other bodies, is NOT equal to zero?
1) 0 – t1; t3 – t4 3) t1 – t2; t2-t3
2) at all time intervals 4) at none of the specified time intervals
Phone interaction. Force. The principle of superposition of forces.
Dynamics
A 1. The student measures the strength of his hand with a spring force meter. In this case, the power ability is used:
I. change the speed of bodies II. cause deformation
1) only I 2) only II 3) both I and II 4) neither I nor II
A 2. Three forces begin to act on a body at rest, shown in fig. Where will the body move?
1) 2) 3) 4)
A 3. What is the angle between the resultant vector of two identical forces and the OX axis, if one
of the forces is co-directed with this axis, and the second forms an angle with the OX axis?
1)
arctg(cos)α
α
/2 2)
α
3) 2
α
4)
Inertia. Newton's first law
A 5. The reference system is connected with the car. It can be considered inertial if the car
1) moves evenly along a straight section of the highway 2) accelerates along a straight section of the highway
3) moves evenly along a winding road 4) rolls uphill by inertia
A 6. The figure shows a graph of the change in the module of the speed of the rectilinear movement of the car with
over time in an inertial frame of reference. At what time intervals is the total force
acting on the car from other bodies, is NOT equal to zero?
1) 0 – t1; t3 – t4 3) t1 – t2; t2-t3
2) at all time intervals 4) at none of the specified time intervals
4) during all the time of its flight
acting on this body?
1) 1 2) 2 3) 3 4) 4
Newton's third law
a book resting on a table?
this cargo?
Dynamics
Newton's second law. Body mass
A 8. The magnet stuck to the vertical wall of the car moving at a constant speed of 50 km / h along a straight section
way. It can be argued that the sum of the forces acting on the magnet
1) is equal to zero in the frame of reference associated with the car, and is not equal to zero in the frame of reference associated with the Earth
2) is not equal to zero in the frame of reference associated with the car, and is equal to zero in the frame of reference associated with the Earth
3) not equal to zero in both frames of reference
4) is equal to zero in reference systems connected with the Earth and with the car
A 9. The athlete makes a high jump. He experiences weightlessness
1) only the time when he flies up to the bar
2) only the time when he flies down after overcoming the bar
3) only the time when at the top point its speed is zero
4) during all the time of its flight
A 10. The left figure shows the velocity and acceleration vectors of the body. Which of the four
The vectors on the right figure indicate the direction of the vector of all acting forces,
acting on this body?
1) 1 2) 2 3) 3 4) 4
Newton's third law
A 12. An apple weighing 0.3 kg falls from a tree. Choose the correct statement
1) the apple acts on the Earth with a force of 3 N, and the Earth does not act on the apple
2) The earth acts on the apple with a force of 3 N, and the apple does not act on the earth
3) the apple and the earth do not act on each other
4) the apple and the Earth act on each other with a force of 3 N
A 13. Which figure correctly shows the forces acting between the table and
a book resting on a table?
A 14. On the floor of an elevator moving with constant acceleration a,
pointing vertically upwards, lies a load of mass m. What is the weight
this cargo?
1) mg 2) 0 3) m (g + a) 4) m (g – a)
