Research in a physics lesson "Determination of the density of a solid body. Is there an air cavity or seal inside the body?" (7th grade)

Introduction

In my practice of teaching physics, the most successful, in my opinion, are examples of lessons in which children themselves have to be in the role of a researcher, think, guess, fantasize and then test their ideas. An important advantage of the natural sciences and, in particular, physics, is the possibility of experimental verification and application of the acquired knowledge. The paper proposes a problem task, as a result of which a new concept is introduced - the density of the body. Students then apply the concept of body density to practical problems.

Target: study and primary consolidation of new knowledge.
Students will study a new physical quantity, determine the density of a solid body in practice. Students will apply the concept of density to solve simple and challenging problems.

(The topic is designed for two lessons of 45 minutes each)

Lesson 1.

King Hieron (250 BC) commissioned a craftsman to make a crown from a single ingot of pure gold. (Appendix 1)
You have been assigned to check the honesty of the master who made the golden crown. At your disposal is a crown and an ingot of gold, the same one that was given to the master. How do you know if the master has replaced some of the gold with a cheap metal, such as iron or copper?
What physical quantities must be measured to answer the question:

Most children immediately guess that it is necessary to compare the masses of the crown and the ingot, for example, using a balance scale. Most likely, even if the master cheated, then another metal was added instead of gold and the mass of the crown would coincide with the mass of the issued ingot. What else needs to be checked? The following hint will help here: put two bodies of the same mass and, preferably, shape, but from different materials (for example, steel and aluminum cylinders) on a balance scale. Children see that the second value for comparison is the volume.
We conclude: if not only the masses, but also the volume of the crown and the volume of the ingot are the same, then the master honestly performed the work.
We discuss the measurement of the volume of bodies of complex shape and talk about Archimedes and his discovery.

Now let's make it harder! What if there is no longer an ingot like the one from which the crown was made, but the king did not guess in advance to measure its mass and volume? Now you have a crown and a small ingot of pure gold (or, for example, a coin) at your disposal, how to answer the same question:

ARE THERE ANY OTHER METALS IN THE GOLDEN CROWN?

Clue:

There is a physical quantity that characterizes the substance of which various bodies are composed. This value is the same for all objects from the same substance. For example, for a gold bar, crown, coin, ring or chain.

WHAT IS THE VALUE?

As a hint, you can suggest compiling such a value from the masses and volumes of bodies already named by the children. In some cases, it is useful to consider all possible combinations using the operations of addition, subtraction, multiplication, division. Thus, we consider the meaninglessness of the m-V, m + V options. The mxV option is not suitable, since this value for the crown will be greater than for the coin. The correct options remain m: V and V: m, one of these options is called density.

Density is a physical quantity that is equal to the ratio of the mass of a body to its volume.

Density of solids (g/cm³ or 1000 kg/m³)

Aluminum
Birch (dry)
			Sand (dry)

Oak (dry)
Spruce (dry)
Iron, steel
			Pine (dry)

The density of gold is r = 19.3 g / cm³, that is, one cubic centimeter contains 19.3 grams of this substance.

Density shows what the mass per unit volume of a given substance is.

Working with the table allows you to discuss quantitatively which materials are the most dense, which are less dense. Textbooks and problem books usually contain the densities of liquids and gases. For memorization, the most important is the density of pure water 1 g/cm³ or 1000 kg/m³. Pay attention to the fact that the density of ice is less than the density of water, which is one of the amazing properties of water, which partly determined the appearance of our planet and the possibility of survival of the inhabitants of reservoirs in winter.

How to use the available reference material?

To practice the application of knowledge about the density of solids, practical work is proposed with a set of bodies of the same volume but different masses. Performing it, the guys determine the density of the body, find the closest value to the value obtained from the table, and thus determine what substance the body is made of.
The first body can be given to everyone the same and, together with the class, parse the definition of the substance by filling in the first line of the table.
Then the rest of the bodies are given out and the children, working in pairs, determine the names of the substances.

Practical work "Determination of the density of a solid substance"

The purpose of the work: to learn how to determine the density of a solid body and, using reference data, find out the substance from which it is made.

Instruments and materials: ruler (caliper), scales, calculator, a set of bodies of the same volume, made from different substances.

Measure the dimensions of the body, calculate its volume (do not forget to write the dimensions of the values).
Measure your body weight on the scales. Record the results in a table.
Calculate the density of the body using the formula

4. Using the reference data, determine the substance of which the body consists, and enter its density and name in the table.

Body mass m, G	body volume V, cm³	Matter density , g/cm³	g/cm³ (from the handbook)	Substance name

Conclusion.
_________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

At the end of the lesson, the name of the substance for each body is given (we place a large printed table on the board) and the children conduct a mutual assessment by exchanging worksheets. We discuss why there is a slight difference between the found densities and the tabulated values (error in determining the volume, body mass; the effect of body temperature on density).

Lesson 2

Research. “Determination of the density of a solid body. Is there an air cavity or seal inside the body?

For this work, each group (pair of students) is given two bodies. One of the bodies is a "reference", that is, it has neither an air cavity nor a seal. It is by comparing the density of the second body with the "reference" that the students answer the question.

Objective:___________________________________________________________
_______________________________________________________________________
Devices and materials: __________________________________________________
_______________________________________________________________________
Hypothesis: ______________________________________________________________
_______________________________________________________________________

For two bodies, do the following and complete the table.

1. Measure your body weight on the scale.
2. Measure the dimensions of the body, calculate its volume.
3. Calculate the density of the body

Make a conclusion and explain it based on the data obtained:
________________________________________________________________________________________________________________________________________________________________________________________________________________________

Conclusion.

tables.

Evaluation and self-assessment of the study.

The bodies for this work are rectangular bars made of various types of wood. Each group examines two bodies made of the same wood: one is the “standard”, the other is the target. In the last body, it is necessary to drill a large diameter hole and paste over with cardboard so that the edges remain smooth. We fill some cavities with metal washers (you can use coins) and we also glue the body with cardboard. Thus, the measurement results and the answer to the question will be different for each group, which will make it possible to qualitatively check the assimilation of the topic. At the same time, it is desirable to choose the sizes of the bars that are noticeably different from each other, then the hypothesis about what is in the body under study, a cavity or a seal, becomes just an assumption. Be sure to warn the children that the mark is not reduced if the assumption was not confirmed. What is important is that children learn to compare the results of measurements and calculations with the initial guess.

At the end of the work, students can write their comments and suggest options for further research on the topic. It will seem interesting to someone to move on to studying the density of liquids (for example, various drinks), for someone, the option to continue working may be to measure the density of bodies of complex shape.

At the end of the lesson, three variants of formulas are written that connect three quantities: mass, volume and density of the body.

Homework consists of several typical tasks for calculating the mass and volume of a body by its density.
Creative task: to compose "tasks from life" for classmates, in the solution of which written formulas will be used.
(for example, find the mass of water in an aquarium with a volume of 50 liters; find the mass of ice that can be placed in a freezer with a volume of 20 liters; bring an ice cream package that indicates the mass and volume, respectively, find the density; tasks to determine materials that can be transported to a car with a known volume of the body (or trunk) and carrying capacity).

Physics

Goals:

consider the concept of “movement” as an information object.
introduce students to the main types of animal movement; show the evolutionary direction in changing the ways of movement;
to form an idea about the body cavity, its types and significance, about the evolutionary direction in changing the type of animal body cavities; repeat the concepts of uniform and uneven movement of “movement”;
develop research skills.

Equipment: tables with images of different groups of animals, computer, multimedia projector, presentation, natural objects.

Lesson type: learning new material

During the classes

I. Organization of the beginning of the lesson

II. Learning new material

1. Knowledge update

(IT-teacher)

Movement is the basis of all life on earth.

Also motion, oddly enough, is one of the foundations in information processes. A striking example of the importance of movement in computer science, and computer science, as you know, is a science that studies information processes, is the formation of animation using information technology. For example, creating a presentation in the Power Point software environment is based on the animation of slide pages and the objects contained in it: text, pictures, diagrams, etc. Animation is the objects given in motion using software. See how interesting you can present information using the program's ability to set objects in motion. Application No. 1. If you pay attention, not only the appearance of the slide is set in motion, but also the objects on it. Application number 2.

Also, based on the movement, the rules for creating animated drawings are based, for example, in the Macromedia Flah program.

Application No. 3.

Application No. 4.

Such dynamics of the object is possible due to various types of movements that a software tool (such as Macromedia Flah) may provide to us. Knowing different ways movements and movement, scientists create computer models and conduct research not on living organisms, but on their computer model. Physicists study physical processes on models that are built on the basis of movements.

(Physics teacher)

Man lives in a world of various movements. Let's remember

what is mechanical movement?
Why is it necessary to indicate in relation to which bodies the body is moving?
what is a trajectory?
what is the path taken by the body?
what kind of movement is called uniform, uneven? Give examples.
how to determine the path traveled by the body in uniform motion, if the speed and time are known? With uneven?
name the basic units of measurement of speed, time, distance traveled.

2) compiling a reference summary for repetition.

3) solution of the problem: determine the speed of the snake if it crawls 2 km in 15 minutes.

(Biology teacher)

The world of wildlife is in constant motion. Herds or flocks of animals, individual organisms move, bacteria and protozoa move in a drop of water. Plants turn their leaves towards the sun, all living things grow. Ways of movement have come a long way in evolution over billions of years

2. Theoretical material

(Biology teacher)

Movement is one of the basic properties of living organisms. Despite the variety of existing active modes of movement, they can be divided into 3 main types: Appendix No. 6 (The presentation accompanies the explanation of the new material)

amoeboid movement.
Movement with flagella and cilia.
Movement with muscles

I. Types of movement of animals.

1. Amoeboid movement

amoeboid movement inherent in rhizopods and some individual cells of multicellular animals (for example, blood leukocytes). So far, biologists have no consensus on what causes amoeboid movement. Outgrowths of the cytoplasm are formed in the cell, the number and size of which are constantly changing, as is the shape of the cell itself.

2. Movement with the help of flagella and cilia.

Movement with the help of flagella and cilia is characteristic not only of flagellates and ciliates, it is inherent in some multicellular animals and their larvae. In highly organized animals, cells with flagella or cilia are found in the respiratory, digestive, and reproductive systems.

The structure of all flagella and cilia is almost the same. Rotating or waving, flagella and cilia create a driving force and twist the body around its own axis. An increase in the number of cilia speeds up movement. This method of movement is usually characteristic of small invertebrates living in the aquatic environment.

But there is an even larger group of animals. And how they move.

3. Movement with the help of muscles.

Movement with muscles occurs in multicellular animals. Typical for invertebrates and vertebrates.

Any movement is a very complex, but well-coordinated activity of large muscle groups and biological, chemical, physical processes in the body.

Muscles are made up of muscle tissue. The main feature of muscle tissue is the ability to contract. Muscle contraction is what causes movement.

In roundworms, alternate contraction of the longitudinal muscles causes characteristic body curves. Due to these body movements, the worm moves forward.

Annelids have mastered new ways of movement due to the fact that in their muscles, in addition to the longitudinal muscles, transverse muscles appeared. Alternately contracting the transverse and longitudinal muscles, the worm, using the bristles on the segments of the body, pushes the soil particles apart and moves forward.

Leeches have mastered walking movements, using suckers to attach. Representatives of the Hydroid class move in “steps”.

In roundworms and annelids, the skin-muscular sac interacts with the fluid contained in it (hydroskeleton).

Gastropods move thanks to the waves of contraction running along the sole of the foot. Abundantly secreted mucus facilitates sliding and accelerates movement. Bivalves move with the help of a muscular leg, and cephalopods have mastered a jet mode of movement, pushing water out of the mantle cavity.

Arthropods are distinguished by an external skeleton.

Many crustaceans use walking legs to move on the ground, and they use either a caudal fin or swimming legs for swimming. Any of these methods of movement is possible in the presence of well-developed muscles and a mobile articulation of the limbs with the body.

Arachnids move on walking legs, and small spiders that form a web can move with the help of the wind.

In most arthropods, not only the legs, but also (depending on the systematic affiliation) other formations, for example, the wings of insects, serve as special organs of locomotion. In grasshoppers with a low wing beat frequency, muscles attach to their bases.

Fish

Physics teacher: let's talk about the floating of bodies from the point of view of physics.

What forces act on a body in a fluid?
What is the direction of these forces?
Under what conditions does a body in a liquid sink, float, or float?

Demonstration experiment with potatoes and salt water, showing three conditions for floating bodies.

How does the depth of immersion in a liquid of a floating body depend on its density? (demonstration experiment with water, sunflower oil and bodies of various densities)
Why don't aquatic animals need strong skeletons?
What role does the swim bladder play in fish?
How do whales regulate their diving depth?
Group work: conducting experiments on various conditions of floating bodies (with the determination of gravity and Archimedean force)

Discussion of the results of experiments, drawing up a reference summary

Powerful muscles run along the body, on both sides of the spine. These lateral muscles are not continuous, but consist of separate plates of muscle segments, or segments, which go one behind the other and are separated from each other by thin fibrous layers (when cooking, these layers are destroyed, and then the boiled meat easily breaks up into separate segments). The number of segments corresponds to the number of vertebrae. When the corresponding muscle fibers contract in any segment, they pull the vertebrae in their direction, and the spine bends; if the muscles on the opposite side contract, then the spine bends in the other direction. Thus, both the fish skeleton and the muscles that dress it have a metameric structure, that is, they consist of repeating homogeneous parts - vertebrae and muscle segments. Muscles provide movement for the fins, jaws, and gill covers. In connection with swimming, the muscles of the back and tail are most developed.

Strong musculature and a hard flexible spine determine the ability of the fish to move quickly in the water.

Amphibians

compared with fish in amphibians, only part of the trunk muscles retains a segmented ribbon-like structure, specialized muscles develop. A frog, for example, has over 350 muscles. The largest and most powerful of them are associated with free limbs.

reptiles

The short limbs of reptiles, located on the sides of the body, do not raise the body high above the ground, and it drags along the ground.

Body undulations are the most common way for snakes to crawl. A calmly crawling snake is an amazingly beautiful and bewitching sight. Nothing seems to be happening. Movement is almost imperceptible. The body seems to lie motionless and at the same time quickly flows. The feeling of ease of movement of the snake is deceptive. In her amazingly strong body, many muscles work synchronously and measuredly, accurately and smoothly transferring the body. Each point of the body in contact with the ground is alternately in the phase of either support, or push, or forward transfer. And so constantly: support-push-transfer, support-push-transfer ... The longer the body, the more bends and the faster the movement. Therefore, in the course of evolution, the body of snakes became longer and longer. The number of vertebrae in snakes can reach 435 (in humans, for comparison, only 32-33).

Crawling snakes can be quite fast. However, even the fastest snakes rarely reach speeds exceeding 8 km/h. The crawl speed record is 16-19 km / h, and it belongs to the black mamba.

There is also a rectilinear, or caterpillar crawling method, and an intermittent course on the sand.

On land, the crocodile's movements are less fast and agile than its movements in the water, where it swims and dives excellently. Its long and muscular tail is compressed from the sides and serves as a good steering oar, and the toes on the hind legs are connected by a swimming membrane. In addition, water also lightens the weight of the body of this overweight animal, dressed in a skin shell of horny scutes and scales, which are located in longitudinal and transverse rows.

When a hummingbird stops (hangs) in the air near a flower, its wings make 50-80 beats per second.

Birds

The most developed (up to 25% of the bird's weight) muscles that move the wings. The most developed in birds are the large pectoral muscles, which lower the wings, which make up 50% of the mass of the entire musculature. Raise the wings of the subclavian muscles, which are also well developed and located under the pectoralis major. The muscles of the hind limbs and neck are strongly developed in birds.

mammals

The muscular system of mammals reaches exceptional development and complexity, it has several hundred muscles. The most developed muscles of the limbs and trunk, which is associated with the nature of movement. The muscles of the lower jaw, chewing muscles, as well as the diaphragm are strongly developed. This is a dome-shaped muscle that delimits the abdominal cavity from the chest. Its role is to change the chest cavity, which is associated with the act of breathing. Significantly developed subcutaneous muscles, setting in motion individual areas of the skin. On the face, it is represented by mimic muscles, especially developed in primates.

3. Movement with the help of muscles. Laboratory work on the topic “Studying the way animals move”, students perform using 3-5 animals from a corner of wildlife, can be replaced by a demonstration)

4. Significance of movement(student report)

5. Body cavities.(The story of a biology teacher)

The body cavity of invertebrates and vertebrates is the space located between the walls of the body and internal organs. For the first time, a body cavity occurs in roundworms. The body cavity of roundworms is called primary, it is filled with abdominal fluid, which not only maintains and preserves the shape of the body, but also performs the function of transporting nutrients in the body, it also accumulates unnecessary waste products. The internal organs of roundworms are freely washed by the abdominal fluid.

The body cavity of annelids, like that of roundworms, extends from the anterior end of the body to the posterior end. In the ringed, it is divided by transverse partitions into separate segments, and each segment, in turn, is divided into two more halves. Each segment has a body cavity filled with abdominal fluid, but unlike the primary one, it is delimited from the internal organs and from the walls of the body by a membrane consisting of a layer of epithelial cells. Such a cavity in which the digestive, excretory, nervous, circulatory systems and the internal walls of the body are not washed by the abdominal fluid and are separated from it by walls consisting of a single layer of epithelial cells is called secondary body cavity.

6. Body cavities.(The story of a biology teacher)

The body cavity of invertebrates and vertebrates is the space located between the walls of the body and internal organs. For the first time, a body cavity occurs in roundworms. The body cavity of roundworms is called primary, it is filled with abdominal fluid, which not only maintains and maintains the shape of the body, but also performs the function of transporting nutrients in the body, it also accumulates unnecessary waste products. The internal organs of roundworms are freely washed by the abdominal fluid.

All chordates have a secondary body cavity. Unlike annelids, the secondary body cavity of chordates does not contain abdominal fluid, and the internal organs are freely located in the cavity.

IV. Consolidation of knowledge

1. Work on cards and drawing up a diagram.

1. How can vertebrates move? (Work according to the scheme. The scheme is drawn up on the board using handouts: cards depicting various animals: (Fish, Amphibians, Reptiles, Birds, Mammals)).

Why can't it be argued that there is a universal way of moving in any habitat?

2. Frontal conversation.

1. Give an explanation why the amoeboid movement is considered “unprofitable”.

2. What are the advantages of movement with the help of cilia and flagella compared to amoeboid movement

3. What methods of animal movement can only be used in the aquatic environment, and which can be used in different ways?

4. Why can't it be argued that there is a universal way of movement in any habitat?

V. Summary of the lesson

1. Reflection

What new did you learn in the lesson? What are the main ways that living organisms move? Will knowing how to get around come in handy in computer science? In physics? Give examples?

VI. Homework

Study § 38, answer the questions at the end of the paragraph.

Filling in the table (using additional literature):

Systematic groups, representatives	Way to travel
Class Hydroids	Walking in steps
Medusa - cornerot	Movement by contraction of muscle fibers
Dairy planaria	Moves with cilia
big pond snail	Movement is carried out by contraction of the muscles of the leg - crawling is smooth and slow
Troop Turtle	Crawls, swim well and deftly cut through the water with their flippers
porcupine porcupine	Thanks to long and sharp claws, though slowly and clumsily, but confidently climbs trees.
Whale	Swims quickly and dexterously (flippers are wide, thick, convex on the front, and strongly concave on the back, tail)

(Distribute sample tables to children on pre-prepared cards)

New materials:

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Did you know, What is the falsity of the concept of "physical vacuum"?

physical vacuum - the concept of relativistic quantum physics, by which they understand the lowest (ground) energy state of a quantized field, which has zero momentum, angular momentum and other quantum numbers. Relativistic theorists call the physical vacuum a space completely devoid of matter, filled with an unmeasurable, and therefore only an imaginary field. Such a state, according to relativists, is not an absolute void, but a space filled with some phantom (virtual) particles. Relativistic quantum field theory claims that, in accordance with the Heisenberg uncertainty principle, virtual particles are constantly born and disappear in the physical vacuum, that is, apparent (seemingly to whom?), particles: the so-called zero-point oscillations of fields occur. The virtual particles of the physical vacuum, and therefore, itself, by definition, do not have a frame of reference, since otherwise Einstein's principle of relativity, on which the theory of relativity is based, would be violated (that is, an absolute measurement system with a reference from the particles of the physical vacuum would become possible, which, in turn, would unequivocally refute the principle of relativity, on which SRT is built). Thus, the physical vacuum and its particles are not elements of the physical world, but only elements of the theory of relativity that exist not in the real world, but only in relativistic formulas, violating the principle of causality (they arise and disappear without a reason), the principle of objectivity (virtual particles can be considered, depending on the desire of the theorist, either existing or non-existing), the principle of actual measurability (not observable, do not have their own ISO).

When one or another physicist uses the concept of "physical vacuum", he either does not understand the absurdity of this term, or is cunning, being a hidden or obvious adherent of the relativistic ideology.

It is easiest to understand the absurdity of this concept by referring to the origins of its occurrence. It was born by Paul Dirac in the 1930s, when it became clear that the negation of the ether in its pure form, as the great mathematician did, but the mediocre physicist, is no longer possible. Too many facts contradict this.

To defend relativism, Paul Dirac introduced the aphysical and illogical concept of negative energy, and then the existence of a "sea" of two energies compensating each other in vacuum - positive and negative, as well as a "sea" of particles compensating each other - virtual (that is, apparent) electrons and positrons in a vacuum.

The black hole boom began in astronomy in the late 1950s and early 1960s. Years passed, much cleared up in this riddle. The inevitability of the birth of black holes after the death of massive stars became clear; discovered quasars, which probably contain supermassive black holes at the center. Finally, the first black hole of stellar origin was discovered in an X-ray source in the constellation Cygnus. Theoretical physicists figured out the outlandish properties of black holes themselves, gradually got used to these gravitational abysses, which can only swallow matter, increasing in size, and, it would seem, doomed to eternal existence.

Nothing foretold a new grandiose discovery. But such a discovery, which amazed the worldly experts, struck like a bolt from the blue.

It turned out that black holes are not eternal at all! They can disappear as a result of quantum processes taking place in strong gravitational fields. We will have to start the story a little from afar in order to make the essence of this discovery more understandable.

Let's start with the void. For a physicist, emptiness is not empty at all. This is not a pun. It has long been established that “absolute” emptiness, that is, “nothing, nothing”, in principle, cannot exist. What do physicists call emptiness? Emptiness is what remains when all particles, all quanta of any physical fields are removed. But then there will be nothing left, the reader will say (if he has not been interested in physics for a long time). No, it turns out it will! What remains, as physicists say, is a sea of unborn, so-called virtual, particles and antiparticles. It is no longer possible to “remove” virtual particles. In the absence of external fields, that is, without communication of energy, they cannot turn into real particles.

Only for a short moment at each point of empty space a pair appears - a particle and an antiparticle and immediately merge again, disappear, returning to their "embryonic" state. Of course, our simplified language gives only some image of the quantum processes that take place. The presence of a sea of virtual particles-antiparticles has long been established by direct physical experiments. We will not talk about it here, otherwise we would inevitably deviate too much from the main line of the story.

To avoid involuntary puns, physicists call emptiness vacuum. We will do the same.

A sufficiently strong or variable field (for example, electromagnetic) can cause the transformation of virtual vacuum particles into real particles and antiparticles.

Theorists and experimenters have shown interest in such processes for a long time. Let us consider the process of production of real particles by an alternating field. It is this process that is important in the case of a gravitational field. It is known that quantum processes are unusual, often unusual for reasoning from the point of view of “common sense”. Therefore, before talking about the creation of particles by an alternating gravitational field, let's give a simple example from mechanics. He will make it clearer.

Imagine a pendulum. Its suspension is thrown over the block, pulling up the rope or lowering it, you can change the length of the suspension. Let's push the pendulum. He will begin to hesitate. The oscillation period depends only on the length of the suspension: the longer the suspension, the longer the oscillation period. Now we will pull the rope very slowly. The length of the pendulum will decrease, the period will also decrease, but the swing (amplitude) of oscillations will increase. Slowly return the rope to its original position. The period will return to its previous value, and the amplitude of the oscillations will also become the same. If we neglect the damping of oscillations due to friction, then the energy contained in the oscillations will remain the same in the final state - such as it was before the entire cycle of changing the length of the pendulum. But it is possible to change the length of the pendulum in such a way that after returning to the original length, the amplitude of its oscillations will change. To do this, you need to pull the rope with a frequency twice the frequency of the pendulum. That's what we do when we're swinging. We lower and tighten our legs to the beat of our swings, and the scope of the swing increases. Of course, you can also stop the swing if you bend your legs not in time with the oscillations, but in “counter-tact”.

In the same way it is possible to "rock" electromagnetic waves in the resonator. This is the name of a cavity with mirror walls that reflect electromagnetic waves. If there is an electromagnetic wave in such a cavity with mirror walls and with a mirror piston, then by moving the piston back and forth with a frequency twice the frequency of the electromagnetic wave, we will change the amplitude of the wave. By moving the piston in “time” with the wave oscillations, it is possible to increase the amplitude, and hence the intensity of the electromagnetic wave, and by moving the piston in the “counter-tact”, it is possible to dampen the wave. But if you move the piston chaotically - both in time and in “counter-tact”, then on average you will always get an amplification of the wave, that is, energy is “pumped” into electromagnetic oscillations.

Let now in our cavity - the resonator there are waves of various frequencies. No matter how we move the piston, there will always be a wave for which the piston moves in time. The amplitude and intensity of this wave will increase. But the greater the intensity of the wave, the more it contains photons-quanta of the electromagnetic field. So, the movement of the piston, changing the size of the resonator, leads to the birth of new photons.

After getting acquainted with these simple examples, let's return to the vacuum, to this sea of all kinds of virtual particles. For simplicity, we will talk about only one kind of particles for the time being - about virtual photons - particles of the electromagnetic field. It turns out that a process similar to the change in the size of the resonator considered by us, which in classical physics leads to the amplification of already existing oscillations (waves), in quantum physics can lead to the “amplification” of virtual oscillations, that is, to the transformation of virtual particles into real ones. Thus, a change in the gravitational field with time should cause the birth of photons with a frequency corresponding to the time of the change in the field. Usually these effects are negligible, since the gravitational fields are weak. However, the situation changes in strong fields.

Another example: a very strong electric field causes the birth of pairs of charged particles - electrons and positrons - from vacuum.

Let's return from our brief excursion into the physics of the void to black holes. Can particles be born from vacuum in the vicinity of black holes?

Yes they can. This has been known for a long time, and there was nothing sensational about it. So, when an electrically charged body is compressed and turned into a charged black hole, the electric field increases so much that it gives rise to electrons and positrons. Similar processes were studied by Academician M. Markov and his students. But such a birth of particles is possible even without a black hole, it is only necessary to increase the electric field by any means to a sufficient value. There is nothing specific to a black hole here.

Academician Ya. Zel'dovich showed that particles are also born in the ergosphere of a rotating black hole, taking away the energy of rotation from it. Such a phenomenon is similar to the process discovered by R. Penrose.

All these processes are caused by the fields around the black hole and lead to a change in these fields, but they do not reduce the black hole itself, they do not reduce the size of the area from which light and any other radiation and particles do not come out.

Novikov I.D.

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Cost of work from 20 000 tenge

COURSE WORKS

The course project is the first serious practical work. It is with writing a term paper that preparation for the development of graduation projects begins. If a student learns to correctly state the content of the topic in a course project and correctly draw it up, then in the future he will have no problems either with writing reports, or with compiling theses, or with performing other practical tasks. In order to assist students in writing this type of student work and to clarify the questions that arise in the course of its preparation, in fact, this information section was created.
Cost of work from 2 500 tenge

MASTER'S THESES

At present, in higher educational institutions of Kazakhstan and the CIS countries, the stage of higher professional education, which follows after the bachelor's degree - the master's degree, is very common. In the magistracy, students study with the aim of obtaining a master's degree, which is recognized in most countries of the world more than a bachelor's degree, and is also recognized by foreign employers. The result of training in the magistracy is the defense of a master's thesis.
We will provide you with up-to-date analytical and textual material, the price includes 2 scientific articles and an abstract.
Cost of work from 35 000 tenge

PRACTICE REPORTS

After completing any type of student practice (educational, industrial, undergraduate) a report is required. This document will be a confirmation of the student's practical work and the basis for the formation of the assessment for the practice. Usually, in order to compile an internship report, you need to collect and analyze information about the enterprise, consider the structure and work schedule of the organization in which the internship takes place, draw up a calendar plan and describe your practical activities.
We will help you write a report on the internship, taking into account the specifics of the activities of a particular enterprise.