Physical bodies made of steel. Interesting online! Crystalline and amorphous
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PHYSICAL BODIES. PHYSICAL PHENOMENA
1. Indicate what belongs to the concept of "physical body" and what to the concept of "substance": airplane, spaceship, copper, fountain pen, porcelain, water, car.
2. Give examples of the following physical bodies: a) consisting of the same substance; b) from various substances of the same name and purpose.
3. Name the physical bodies that can be made of glass, rubber, wood, steel, plastic.
4. Indicate the substances that make up the following bodies: scissors, glass, football camera, shovel, pencil.
5. Draw a table in a notebook and distribute the following words in it: lead, thunder, rails, blizzard, aluminum, dawn, snowstorm, moon, alcohol, scissors, mercury, snowfall, table, copper, helicopter, oil, boiling, blizzard, shot , flood.
6. Give examples of mechanical phenomena.
7. Give examples of thermal phenomena.
8. Give examples of sound phenomena.
9. Give examples of electrical phenomena.
10. Give examples of magnetic phenomena.
11. Give examples of light phenomena.
12. Draw the table below in a notebook and write down the words related to mechanical, sound, thermal, electrical, light phenomena, the ball rolls, lead melts, gets cold, thunder is heard, snow melts, stars twinkle, water boils, dawn comes, echo , a log floats, the clock pendulum oscillates, clouds move, a thunderstorm, a dove is flying, lightning flashes, foliage rustles, an electric lamp is on.
13. Name two or three "physical phenomena that are observed when firing a cannon."
MEASUREMENT OF PHYSICAL QUANTITIES
14. Imagine a 3-kopeck coin and a soccer ball. Think about how many times the diameter of the ball is larger than the diameter of the coin. (To check the answer, see table 11.)
15. a) The hair thickness is 0.1 mm. Express this thickness in cm, m, micron, nm. b) The length of one of the bacteria is 0.5 μm. How many such bacteria would be packed "close to the length of 0.1 mm, 1 mm, 1 cm?"
16. In Ancient Babylon, the distance that an adult traveled during the time the disk of the Sun was out of the horizon was taken as a unit of length. This unit was called a stage. Could such a unit of length be accurate? Explain the answer.
17. What is the length of the bar shown in Figure 1?
18. Figure 2 shows how the diameter of a ball can be measured. Define it. Using this method, determine the diameter of the ball you are playing.
19. Figure 3 shows parts of the bars and rulers. The left ends of the bars coincide with the zero marks of the rulers, which is not shown in the figure, and the right ends relative to the numerical marks of the scale are located as shown in the figure. Determine by eye the length of each bar, if
the division price of the rulers is 1 cm.
Figure: 1
Figure: 2
Fig 3
20. Taking into account what fraction of the scale division value, you can measure the lengths of small objects with the rulers shown in Figure 4, a, b, c, d?
21 °. To determine the diameter of the wire, the student wound 30 turns close to the pencil, which took up a part of the pencil 3 cm long (Fig. 5). Determine the wire diameter.
22 °. Determine the circumference of the head of the screw or nail once using the method shown in Figure 6, another time by measuring the diameter and multiplying it by the number L. Compare the measurement results and write them down in a notebook.
Figure: 4
Figure: five
Figure: 6
Figure: 7
Figure: 8
23. Take several identical coins, fold them as shown in Figure 7, and measure the thickness of the resulting stack with a millimeter ruler. Determine the thickness of one coin. In which case the thickness of one coin will be measured more qualitatively: with a small or large number of coins?
24. How to use a measuring ruler to determine the average diameters of small homogeneous objects, such as millet grains, lentils, pinheads, poppy seeds, etc.?
25. a) During the construction of the house, a reinforced concrete slab 5.8 m long and 1.8 m wide was laid. Determine the area occupied by this slab, b) In any circus in the world, the diameter of the arena is 13 m. What area does the arena occupy in the circus?
26. How long will be the strip, consisting of pieces of I cm 2 cut from a sheet of 1 m 2?
27. Having measured the diameter of the circle shown in Figure 8, calculate its area. Determine the area of \u200b\u200bthe circle by counting the squares in it. Compare your numerical results.
28. Determine the volume of a rectangular bar, which is 1.2 m long, 8 cm wide and 5 cm thick.
29. Having measured the length, width and height of your room, determine its volume.
30. The height of the granite column is 4 m, the base of the column is a rectangle with sides 50 and 60 cm. Determine the volume of the column.
31. What are the volumes of liquids in the beakers shown in Figure 9?
32. What are the similarities and differences between the scales of the beakers shown in Figure 10?
Figure: nine
Figure: ten
33. A body of irregular geometric shape is lowered into a beaker with water (Fig. 11). Determine the graduation rate of the beaker and the volume of the body.
34. How to determine the volume of one pellet if given a beaker, shot, water?
35. Explain, using Figure 12, how you can determine the volume of a body that does not fit in a beaker.
Figure: eleven
Figure: 12
Figure: 13
36. With what accuracy can the time be measured with the stopwatch shown in Figure 13?
37. The winner of the school in track and field athletics ran a distance of 100 meters in the time shown on the stopwatch in Figure 13. Express this time in minutes, hours; milliseconds, microseconds.
3§. At night the air temperature was -6 ° С, and during the day + 4 ° С. How many degrees did the air temperature change?
Figure: fourteen
39. Determine the value of the division of the scale of each thermometer (Fig. 14). What is the maximum temperature that can be measured with the thermometers shown in Figure 14, b, e; minimum (Fig. 14, a, d)? What temperature does each thermometer show?
STRUCTURE OF SUBSTANCE
40. Oil is compressed in a thick-walled steel cylinder. Under high pressure, oil droplets protrude on the outer walls of the cylinder. How can this be explained?
41. In the photograph, the apparent diameter of a molecule of some substance is 0.5 mm. What is the actual diameter of a molecule of a given substance if the photograph was obtained using an electron microscope with a magnification of 200,000 times?
Figure: 15
42. A drop of oil with a volume of 0.003 mm3 spread over the water surface in a thin layer and occupied an area of \u200b\u200b300 cm2. Assuming the thickness of the layer equal to the diameter of the oil molecule, determine this diameter.
43. The length of the column of mercury in the room thermometer tube has increased. Did this increase the number of mercury molecules? Has the volume of each mercury molecule in the thermometer changed?
44. Is it possible to say that the volume of a gas in a vessel is equal to the sum of the volumes of its molecules?
45. Do the gaps between the molecules of any substance in solid, liquid and gaseous states differ at the same temperature?
46. \u200b\u200bThe rubber cord lengthened due to the load. Did the gaps between the rubber particles change?
47. Under the action of the load, the piston in the cylinder lowered (Fig. 15). When the load was removed, the piston took the same
position /. How did the ratio of the volume of air under the piston change to the sum of the volumes of its molecules?
48. Give an example of experience confirming that a substance consists of molecules separated by intervals.
49. Are the volumes and composition of cold and hot water molecules the same?
50. Are the volumes and composition of molecules the same for different substances?
51. The ratio of an arbitrary volume of water to the sum of the volumes of molecules of the same water and the ratio of the same volume, steam to the sum of volumes of molecules of the same vapor. Slick attitude more?
52. How do the gaps between the particles of the copper rivet change during heating and cooling?
53. What explains the increase in the length of the wire when it is heated?
54. Why does the length of the rail decrease when it cools?
55. Why is the temperature indicated on precision measuring instruments (usually 20 ° C)?
MOTION OF MOLECULES AND BODY TEMPERATURE
56. What explains the spread in the air of smells of gasoline, smoke, naphthalene, perfume and other odorous substances?
57. Gas molecules move at speeds of the order of several hundred meters per second. Why do we not instantly feel the smell of ether or gasoline spilled near us in the air?
58. An open vessel with carbon dioxide was balanced on a balance. Why has the balance of the weights been disturbed over time?
59. A child's rubber balloon filled with hydrogen becomes slightly inflated after a few hours. Why?
60. Why does the smoke from a fire stop being visible as it rises, even in calm weather?
61. Why diffusion in gases and liquids proceeds much faster than in solids?
62. In the old book in front of the pages with drawings, sheets of thin transparent paper are glued. Did the prints of the drawing appear over time on the sides of this paper in contact with the drawings?
63. A marine animal squid, when attacked, emits a dark blue protective liquid. Why does the space filled with this liquid become transparent after a while, even in calm water?
64. If you examine a drop of highly diluted milk through a microscope, you can see that small drops of oil floating in the liquid move continuously. Explain this phenomenon.
65. Identical sugar lumps were thrown into glasses of water at the same time. In which glass was the initial water temperature higher (Fig. 16)?
66. Why is it not recommended to leave wet dark-colored cloth in contact with white cloth for a long time? Explain what is happening.
67. How can you accelerate diffusion in solids?
68. Where is the best place to store a hydrogen-filled baby rubber ball: in a cold or warm room?
69. One jug of milk was put in the refrigerator, the other was left in the room. Where will the cream settle faster?
Figure: sixteen
INTERACTION OF MOLECULES
70. Molecules of a solid are in constant motion. Why don't solids disintegrate into separate molecules?
71. Why can't we connect the broken pencil so that it becomes whole again?
72. Why doesn't dust rise on the road after rain?
73. Why does it take much more effort to separate sheets of paper moistened with water than when turning over dry pages of a book?
74. Why is it written on the blackboard with chalk and not with a piece of white marble? What can be said about the interaction between the particles of these substances?
75. Which substances (lead, wax, steel) have the greatest attraction between particles; the fewest?
76. Plane end measures of length (Johansson tiles) are polished so that upon contact they stick to each other and mutually hold (Fig. 17). Explain the reason for this phenomenon.
77. Welding of metal parts can also be performed in a cold way, if they are connected and squeezed very hard. Under what condition can such welding be performed?
78. The glass plate, suspended on a rubber cord, was lowered until it touched the surface of the water (Fig. 18). Why does the cord stretch when the record is lifted?
79. In what state - solid or liquid - is the attraction between lead molecules greater?
80. Oil is relatively easy to remove from clean copper surfaces. It is impossible to remove mercury from the same surface. What about the mutual attraction between the molecules of oil and copper, mercury and copper?
81. Molecules of a substance are attracted to each other. Why are there gaps between them?
82. What is common between paper gluing and metal soldering?
83. What is the difference between welding of metal parts from soldering metal
products?
Figure: 17
Figure: 18
THREE STATES OF SUBSTANCE
84. In what state are the following substances at room temperature: water, sugar, air, tin, alcohol, ice, oxygen, aluminum, milk, nitrogen? Write the answers in the table by drawing it in notebooks.
|
condition |
||
|
gaseous |
||
85. Can an open vessel be filled with gas to 50% of its capacity?
86. A closed bottle is half filled with mercury. Can we say that there is no mercury in the upper half of the bottle?
87. Can oxygen and nitrogen be in a liquid state? 88. * Can mercury be in a gaseous state,
iron, lead?
89. On a summer evening, fog formed over the swamp. What is the condition of the water?
90. On a frosty winter day, fog formed over the hole in the river. What is the condition of the water?
91. The dog "takes" a fresh, albeit invisible, track (for example, of a hare). However, over time, she cannot smell it. Explain this phenomenon.
92. Kerosene was stored in a polystyrene flask for a long time. If you pour milk into this, even very thoroughly washed, flask, then in it we will still smell the smell of kerosene. Explain why.
93. A piece of tin was heated, and it acquired a liquid state. How did the movement change towards the arrangement of the pieces of tin relative to each other?
94. The water has evaporated and turned into steam. Did the water molecules themselves change? How has their location and movement changed?
In today's article, we will speculate about what a physical body is. this term has already met you more than once during the years of schooling. For the first time we come across the concepts "physical body", "substance", "phenomenon" in the lessons of natural history. They are the subject of study of most sections of the special science - physics.
According to "physical body" denotes a certain material object that has a form and a pronounced external boundary that separates it from the external environment and other bodies. In addition, the physical body has characteristics such as mass and volume. These parameters are basic. But besides them, there are others. We are talking about transparency, density, elasticity, hardness, etc.
Physical bodies: examples
Simply put, we can call any of the surrounding objects a physical body. The most common examples are a book, a table, a car, a ball, a cup. Physics calls a simple body one whose geometric shape is simple. Composite physical bodies are those that exist in the form of combinations of simple bodies connected to each other. For example, a very conventionally human figure can be represented as a collection of cylinders and balls.
The material of which any of the bodies consists is called substance. Moreover, they can contain in their composition both one and a number of substances. Here are some examples. Physical bodies are cutlery (forks, spoons). They are most often made of steel. A knife is an example of a body made up of two different kinds of substances - a steel blade and a wooden handle. And something as complex as a cell phone is made from many more "ingredients."
What are the substances
They can be natural and artificial. In ancient times, people made all the necessary items from natural materials (arrowheads - from clothes - from animal skins). With the development of technological progress, substances created by man appeared. And at the present time those are the majority. Plastic is a classic example of an artificial physical body. Each of its types was created by a person in order to ensure the necessary qualities of this or that object. For example, transparent plastic - for glasses lenses, non-toxic food - for dishes, durable - for a car bumper.
Any item (from to a high-tech device) has a number of specific qualities. One of the properties of physical bodies is their ability to be attracted to each other as a result of gravitational interaction. It is measured using a physical quantity called mass. Physicists define the mass of bodies as a measure of their gravity. It is denoted by the symbol m.
Mass measurement
This physical quantity, like any other, is measurable. To find out what the mass of any object is, you need to compare it with a standard. That is, with a body, the mass of which is taken as a unit. The International System of Units (SI) is the kilogram. This "ideal" unit of mass exists in the form of a cylinder, which is an alloy of iridium and platinum. This international design is kept in France and copies are available in almost every country.
In addition to the kilogram, the concept of a ton, a gram or a milligram is used. Measure the same body weight by weighing. This is the classic way for everyday calculations. But in modern physics there are others that are much more modern and highly accurate. With their help, the mass of microparticles, as well as giant objects, is determined.
Other properties of physical bodies
Shape, mass and volume are the most important characteristics. But there are other properties of physical bodies, each of which is important in a certain situation. For example, objects of equal volume can differ significantly in their mass, that is, have different densities. In many situations, characteristics such as fragility, hardness, resilience, or magnetic properties are important. We should not forget about thermal conductivity, transparency, homogeneity, electrical conductivity and many other physical properties of bodies and substances.
In most cases, all such characteristics depend on the substances or materials of which the objects are composed. For example, rubber, glass and steel balls will have completely different sets of physical qualities. This is important in situations of interaction of bodies with each other, for example, the study of the degree of their deformation when they collide.
About the adopted approximations
Certain sections of physics consider the physical body as a kind of abstraction with ideal characteristics. For example, in mechanics, bodies are represented as material points that do not have mass or other properties. This branch of physics deals with the movement of such conventional points, and for solving the problems posed here, such quantities are not of fundamental importance.
In scientific calculations, the concept of an absolutely rigid body is often used. This is conventionally considered a body not subject to any deformations, with no displacement of the center of mass. This simplified model allows you to theoretically reproduce a number of specific processes.
The section of thermodynamics uses the concept of a black body for its own purposes. What is it? A physical body (some abstract object) capable of absorbing any radiation that falls on its surface. Moreover, if the task requires it, they can be emitted by electromagnetic waves. If, according to the conditions of theoretical calculations, the shape of physical bodies is not fundamental, by default it is assumed that it is spherical.
Why the properties of bodies are so important
Physics itself as such arose from the need to comprehend the laws by which physical bodies behave, as well as the mechanisms of the existence of various external phenomena. Natural factors include any changes in our environment that are not related to the results of human activity. Many of them are used by people to their advantage, but others can be dangerous and even disastrous.
The study of behavior and various properties of physical bodies is necessary for people in order to predict adverse factors and prevent or reduce the harm they cause. For example, by building breakwaters, people are used to fighting the negative manifestations of the sea. Humanity has learned to resist earthquakes by developing special seismic-resistant structures of buildings. The load-bearing parts of the vehicle are manufactured in a special, carefully calibrated form to reduce damage in accidents.
About the structure of bodies
According to another definition, the term "physical body" means everything that can be recognized as real. Any of them necessarily occupies a part of space, and the substances of which they are composed are a set of molecules of a certain structure. Other, smaller particles of it are atoms, but each of them is not something indivisible and completely simple. The structure of the atom is quite complex. In its composition, positive and negatively charged elementary particles - ions can be distinguished.
The structure according to which such particles are arranged in a certain system is called crystalline for solids. Any crystal has a definite, strictly fixed shape, which speaks of the ordered movement and interaction of its molecules and atoms. When the crystal structure changes, the physical properties of the body are violated. Its state of aggregation, which can be solid, liquid or gaseous, depends on the degree of mobility of the elementary components.
To characterize these complex phenomena, the concept of compression coefficients or bulk elasticity, which are mutually reciprocal values, is used.
Movement of molecules
The state of rest is not inherent in either atoms or molecules of solids. They are in constant motion, the nature of which depends on the thermal state of the body, and the influences to which it is currently exposed. Part of elementary particles - negatively charged ions (called electrons) move at a higher speed than those with a positive charge.
From the point of view of the state of aggregation, physical bodies are solid objects, liquids or gases, which depends on the nature of molecular motion. The entire set of solids can be divided into crystalline and amorphous. The movement of particles in the crystal is recognized to be completely ordered. In liquids, molecules move in a completely different way. They move from one group to another, which can be figuratively represented as comets wandering from one heavenly system to another.
In any of the gaseous bodies, the molecules have a much weaker bond than in liquid or solid. The particles there can be called repelling from each other. The elasticity of physical bodies is determined by a combination of two main quantities - the shear coefficient and the bulk elasticity coefficient.
Fluidity of bodies
With all the significant differences between solid and liquid physical bodies, their properties have much in common. Some of them, called soft, occupy an intermediate state of aggregation between the first and the second with physical properties inherent in both. A quality such as fluidity can be found in a solid (for example, ice or boot pitch). It is also inherent in metals, including rather hard ones. Most of them are capable of flowing like a liquid under pressure. By connecting and heating two solid pieces of metal, it is possible to solder them into a single whole. Moreover, the soldering process takes place at a temperature much lower than the melting point of each of them.
This process is possible provided that both parts are in full contact. It is in this way that various metal alloys are obtained. The corresponding property is called diffusion.
About liquids and gases
According to the results of numerous experiments, scientists have come to the following conclusion: solid physical bodies are not some isolated group. The difference between them and liquid ones consists only in greater internal friction. The transition of substances into different states occurs under conditions of a certain temperature.
Gases differ from liquids and solids in that an increase in the elastic force does not occur even with a strong change in volume. The difference between liquids and solids is in the appearance of elastic forces in solids during shear, that is, a change in shape. This phenomenon is not observed in liquids, which can take any of the forms.
Crystalline and amorphous
As already mentioned, two possible states of solids are amorphous and crystalline. Amorphous bodies are bodies that have the same physical properties in all directions. This quality is called isotropy. Hardened resin, amber products, glass can be cited as examples. Their isotropy is the result of the disordered arrangement of molecules and atoms in the composition of matter.
In the crystalline state, elementary particles are arranged in a strict order and exist in the form of an internal structure that periodically repeats in different directions. The physical properties of such bodies are different, but in parallel directions they coincide. This property inherent in crystals is called anisotropy. Its cause is the unequal strength of interaction between molecules and atoms in different directions.
Mono- and polycrystals
In single crystals, the internal structure is homogeneous and repeats throughout the entire volume. Polycrystals look like many small crystallites randomly intergrown with each other. Their constituent particles are located at a strictly defined distance from each other and in the right order. A crystal lattice is understood as a set of nodes, that is, points that serve as centers of molecules or atoms. Crystalline metals serve as material for the framework of bridges, buildings and other durable structures. That is why the properties of crystalline bodies are carefully studied for practical purposes.
Real strength characteristics are negatively affected by crystal lattice defects, both surface and internal. A separate section of physics, called solid mechanics, is devoted to similar properties of solids.
November 9th, 2018In the minds of an ordinary man in the street, a strong opinion has been strengthened that with the moment of physical death all biological processes in the body of the deceased stop, and his body gradually begins to decompose. In fact, this theory is far from the truth. After a person's heart stops beating and the brain loses control over the body, residual physiological processes still occur in some parts of the body. The 10 functions of the body that do not fade away after the death of a person will be discussed further.
10. Digestion
Who would have thought that when a person leaves this world, his digestive tract continues not only to expel the digested food, but also to some extent to digest it. This is due to the fact that many microorganisms live in our body, some of which are an integral link in the mechanism of food digestion. When a person dies, the life of these bacteria does not stop, and they continue to actively fulfill their biological purpose. In addition, some of them are involved in the production of gas, thanks to which lumps of digested food can move through the dead intestine.
9. Erection and ejaculation
In abstract terms, the heart muscle is a physiological pump that pumps blood from one part of the body to another. When this organ ceases to function, blood circulation stops, which causes blood to accumulate in the lowest place in the body. If a person dies in a standing position or lying on his stomach, then it is not difficult to guess where most of his blood will collect. In addition, certain groups of muscle cells are activated by calcium ions after death. Due to this, after the actual onset of death, the onset of an erection with subsequent ejaculation is possible.
8. Growth of nails and hair
It is difficult to put this function on a par with the others given in this article, since it is rather an external feature of almost all dead bodies than a really biological process that is active after a person's death. Of course, inanimate cells cannot reproduce either hair or nails, however, after death, the skin loses moisture, which is why it is slightly pulled back, exposing some part of the hair that was previously in the thickness of the skin. At the same time, it visually gives the impression that the hair and nails of the deceased are really growing.
7. Muscle movement
After the death of the brain, some parts of the nervous system may remain in a state of activity for some time. Scientists have more than once recorded in dead patients the occurrence of reflexes, in which an impulse went through the nerve fibers not to the brain, but to the spinal cord, due to which the deceased had muscle twitching or spasm.
6. Brain activity
In modern medicine, situations often occur when the brain has actually died, and the heart continues to function. The opposite and no less common situation - when cardiac arrest occurs, the brain technically continues to live for several more minutes. At this time, brain cells use all possible resources in order to seek out oxygen and nutrients necessary for the continuation of vital activity. This short period, within which it is still possible to restore the normal functioning of the brain, in our time it is quite possible to extend to several days with the help of certain drugs and with the necessary measures.
5. Urination
Many people think that the physiological act of passing urine is completely arbitrary. However, this is not quite true. Our consciousness does not really control this mechanism - a certain part of the cerebral cortex is responsible for it. In addition, this zone is actively involved in the regulation of the respiratory system and cardiac activity. With rigor mortis, the muscles should, as it were, freeze, but this does not happen for some time after death. At the very moment of death, smooth and skeletal muscles relax, due to which the external sphincter of the urethra opens and, accordingly, urine flows.
Narcotic substances and alcohol have a depressing effect on the work of the area of \u200b\u200bthe cerebral cortex responsible for urination. Therefore, people under the influence of these substances often experience involuntary urine flow.
4. Growth of skin cells
Oddly enough, this function also does not fade away immediately after death. Skin cells are one of the few in the human body that do not need continuous blood supply. Therefore, from the moment of cardiac arrest, they continue to function for some time and reproduce their own kind.
3. The birth of a child
Documents have reached our time confirming that in the history of mankind there have been cases of the so-called "posthumous delivery." The essence of this ritual is that if a woman dies late in pregnancy, then she is not buried until her body pushes the fetus out. This mechanism is due to the accumulation of gases inside the body, which serve as a kind of driving force leading the fetus along the birth canal.
2. Defecation
For many of us it is no secret that in moments of intense excitement, our body seeks to get rid of the end products of life. This happens because in a moment of stress, certain muscle groups relax sharply, which leads to a slight embarrassment. If we talk about the physical death of a person, then in this case, the implementation of postmortem defecation is facilitated not only by the relaxation of all muscles, but also by the increased production of gases in the intestine, which occurs as a result of the death of organic tissues. The passage of feces can occur a few hours or a day after death.
1. Vocalization
This function is very sinister, especially if you do not know the nature of this phenomenon. Rigor mortis affects nearly all muscle groups, including those that function within the vocal apparatus. Because of this, the dead body can produce soft sounds that resemble moans or wheezing.
In the minds of an ordinary man in the street, a strong opinion has been strengthened that with the moment of physical death all biological processes in the body of the deceased stop, and his body gradually begins to decompose. In fact, this theory is far from the truth. After a person's heart stops beating and the brain loses control over the body, residual physiological processes still occur in some parts of the body. The 10 functions of the body that do not fade away after the death of a person will be discussed further.
10. Digestion
Who would have thought that when a person leaves this world, his digestive tract continues not only to expel the digested food, but also to some extent to digest it. This is due to the fact that many microorganisms live in our body, some of which are an integral link in the mechanism of food digestion. When a person dies, the life of these bacteria does not stop, and they continue to actively fulfill their biological purpose. In addition, some of them are involved in the production of gas, thanks to which lumps of digested food can move through the dead intestine.
9. Erection and ejaculation
In abstract terms, the heart muscle is a physiological pump that pumps blood from one part of the body to another. When this organ ceases to function, blood circulation stops, which causes blood to accumulate in the lowest place in the body. If a person dies in a standing position or lying on his stomach, then it is not difficult to guess where most of his blood will collect. In addition, certain groups of muscle cells are activated by calcium ions after death. Due to this, after the actual onset of death, the onset of an erection with subsequent ejaculation is possible.
8. Growth of nails and hair
It is difficult to put this function on a par with the others given in this article, since it is rather an external feature of almost all dead bodies than a really biological process that is active after a person's death. Of course, inanimate cells cannot reproduce either hair or nails, however, after death, the skin loses moisture, which is why it is slightly pulled back, exposing some part of the hair that was previously in the thickness of the skin. At the same time, it visually gives the impression that the hair and nails of the deceased are really growing.
7. Muscle movement
After the death of the brain, some parts of the nervous system may remain in a state of activity for some time. Scientists have more than once recorded in dead patients the occurrence of reflexes, in which an impulse went through the nerve fibers not to the brain, but to the spinal cord, due to which the deceased had muscle twitching or spasm.
6. Brain activity
In modern medicine, situations often occur when the brain has actually died, and the heart continues to function. The opposite and no less common situation - when cardiac arrest occurs, the brain technically continues to live for several more minutes. At this time, brain cells use all possible resources in order to seek out oxygen and nutrients necessary for the continuation of vital activity. This short period, within which it is still possible to restore the normal functioning of the brain, in our time it is quite possible to extend to several days with the help of certain drugs and with the necessary measures.
5. Urination
Many people think that the physiological act of passing urine is completely arbitrary. However, this is not quite true. Our consciousness does not really control this mechanism - a certain part of the cerebral cortex is responsible for it. In addition, this zone is actively involved in the regulation of the respiratory system and cardiac activity. With rigor mortis, the muscles should, as it were, freeze, but this does not happen for some time after death. At the very moment of death, smooth and skeletal muscles relax, due to which the external sphincter of the urethra opens and, accordingly, urine flows.
Narcotic substances and alcohol have a depressing effect on the work of the area of \u200b\u200bthe cerebral cortex responsible for urination. Therefore, people under the influence of these substances often experience involuntary urine flow.
4. Growth of skin cells
Oddly enough, this function also does not fade away immediately after death. Skin cells are one of the few in the human body that do not need continuous blood supply. Therefore, from the moment of cardiac arrest, they continue to function for some time and reproduce their own kind.
3. The birth of a child
Documents have reached our time confirming that in the history of mankind there have been cases of the so-called "posthumous delivery." The essence of this ritual is that if a woman dies late in pregnancy, then she is not buried until her body pushes the fetus out. This mechanism is due to the accumulation of gases inside the body, which serve as a kind of driving force leading the fetus along the birth canal.
2. Defecation
For many of us it is no secret that in moments of intense excitement, our body seeks to get rid of the end products of life. This happens because in a moment of stress, certain muscle groups relax sharply, which leads to a slight embarrassment. If we talk about the physical death of a person, then in this case, the implementation of postmortem defecation is facilitated not only by the relaxation of all muscles, but also by the increased production of gases in the intestine, which occurs as a result of the death of organic tissues. The passage of feces can occur a few hours or a day after death.
1. Vocalization
This function is very sinister, especially if you do not know the nature of this phenomenon. Rigor mortis affects nearly all muscle groups, including those that function within the vocal apparatus. Because of this, the dead body can produce soft sounds that resemble moans or wheezing.
If I wanted to read, not yet
knowing the letters, it would be nonsense.
Likewise, if I wanted to judge
about natural phenomena without any
ideas about the beginnings of things, this
would be the same nonsense.
M.V. Lomonosov
Look around you. What a variety of objects surrounds you: these are people, animals, trees. This is a TV, a car, an apple, a stone, a light bulb, a pencil, etc. It is impossible to list everything. In physics any object is called a physical body.
Figure: 6
How are physical bodies different? To many. For example, they can have different volumes and shapes. They can be composed of different substances. Silver and gold spoons (fig. 6) have the same volume and shape. But they consist of different substances: silver and gold. Wooden cube and ball (fig. 7) have different volume and shape. These are different physical bodies, but made of the same substance - wood.
Figure: 7
In addition to physical bodies, there are also physical fields. The fields exist independently of us. They are not always detectable with the human senses. For example, a field around a magnet (Fig. 8), a field around a charged body (Fig. 9). But they are easy to spot with instruments.
Figure: 8
Figure: nine
Various changes can occur with physical bodies and fields. A spoon dipped in hot tea heats up. The water in the puddle evaporates and freezes on a cold day. The lamp (Fig. 10) emits light, the girl and the dog run (move) (Fig. 11). The magnet is demagnetized and its magnetic field is weakened. Heating, evaporation, freezing, radiation, movement, demagnetization, etc. - all these changes occurring with physical bodies and fields are called physical phenomena.
Figure: ten
By studying physics, you will become familiar with many physical phenomena.
Figure: eleven
To describe the properties of physical bodies and physical phenomena, physical quantities are introduced... For example, you can describe the properties of a wooden ball and a cube using such physical quantities as volume, mass. A physical phenomenon - movement (girls, cars, etc.) - can be described knowing such physical quantities as path, speed, time interval. Pay attention to the main sign of physical size: it can be measured with instruments or calculated by the formula... The volume of the body can be measured with a beaker with water (Fig. 12, a), or, by measuring the length a, width b and height with a ruler (Fig. 12, b), calculate by the formula
V \u003d a. b. c.
All physical quantities have units of measurement. You have heard about some units of measurement many times: kilogram, meter, second, volt, ampere, kilowatt, etc. You will get acquainted in more detail with physical quantities in the process of studying physics.
Figure: 12
Think and answer
- What is called the physical body? A physical phenomenon?
- What is the main sign of physical size? What are the physical quantities known to you?
- From the given concepts, name those that relate to: a) physical bodies; b) physical phenomena; c) physical quantities: 1) drop; 2) heating; 3) length; 4) thunderstorm; 5) a cube; 6) volume; 7) wind; 8) drowsiness; 9) temperature; 10) pencil; 11) time span; 12) sunrise; 13) speed; 14) beauty.
Homework
We have a "measuring device" in our body. This is a heart with which you can measure (with not very high accuracy) a period of time. Determine by the pulse (number of heart beats) the time interval for filling the glass with tap water. Consider the time of one hit to be approximately equal to one second. Compare this time with your watch. How different are the results obtained?
