In nature, only four main fundamental forces are known (they are also called basic interactions) - gravitational interaction, electromagnetic interaction, strong interaction and weak interaction.

Gravitational interaction is the weakest of all.Gravitational forces Bind together part of the globe and the same interaction determines large-scale events in the universe.

Electromagnetic interaction holds electrons in atoms and binds atoms into molecules. Private manifestation of these forces are Coulomb forcesacting between fixed electrical charges.

Strong interaction binds nucleons in nuclei. This interaction is the strongest, but it only acts on very short distances.

Weak interaction acts between elementary particles and has a very small range. It manifests itself with beta decay.

4.1. Newton World Worldwide

There is a mutual attraction force between two material points, directly proportional to the product of the masses of these points (m. andM. ) and inversely proportional to the square of the distance between them (r 2. ) and directed along the direct passing through the interacting bodiesF.\u003d (GMM / R 2) r. o. ,(1)

here r. o. - Unit vector spending in the direction of force F.(Figure 1a).

This power is called gravitational power (or force world full gravity ). Gravitational forces are always attraction forces. The strength of the interaction between two bodies does not depend on the environment in which the bodies are.

g. 1 g. 2

Fig.1a Fig.1b Fig.1s

Permanent G called gravitational constant. Its value is established by experimental pathway: G \u003d 6.6720. 10 -11 N. m 2 / kg 2 - i.e. Two point body mass in 1 kg each, located at a distance of 1 m from each other, are attracted with 6.6720. 10 -11 N. A very small value of G just allows us to talk about the weakness of gravitational forces - they should be taken into account only in the case of large masses.

Masses included in equation (1) are called gravitational masses. This emphasizes that in principle, the masses included in Newton's second law ( F.\u003d M In. a.) and into the law of world community ( F.\u003d (Gm gr m gr / r 2) r. o.), have different nature. However, it was established that the ratio M GR / M in for all bodies is equally with a relative error of up to 10 -10.

4.2. Governmental field (field) material point

It's believed that gravitational interaction is carried out using gravitational field (fields of gravity), which is generated by the bodies themselves. Two characteristics of this field are introduced: vector - and scalar - the potential of the gravitational field.

4.2.1. The lack of a gravitational field

Let we have a material point with a mass of M. It is believed that a gravitational field occurs around this mass. The power characteristic of this field is the tension of the gravitational fieldg.which is determined from the law of world g.\u003d (GM / R 2) r. o. ,(2)

where r. o. - a single vector conducted from the material point in the direction of the gravitational force. The tension of the gravitational field g.there is a vector magnitude and is an acceleration obtained by a point mass. m, entered in the gravitational field created by the point massM. Indeed, comparing (1) and (2), we obtain for the case of equality of gravitational and inert masses F.\u003d M. g.

We emphasize that the magnitude and direction of acceleration obtained by the body entered into the gravitational field does not depend on the magnitude of the mass of the injected body.. Since the main task of the speaker is to determine the amount of acceleration obtained by the body under the action of external forces, then, therefore, the tension of the gravitational field completely and uniquely determines the power characteristics of the gravitational field.. The dependence G (R) is shown in Fig. 2a.

Fig.2A Fig.2b Fig.2S

The field is called central, if at all points of the field, the tension vectors are directed along direct, which intersect in one point, fixed with respect to any inertial reference system. In particular, the gravitational field of the material point is central: in all points of the field, the vectors g.and F.\u003d M. g., acting on the body, entered in the gravitational field, are directed radially from the massM. creating a field to the point massm. (Fig. 1b).

The law of global gravity in the form (1) is established for bodies adopted for material Points. For such bodies, the dimensions of which are small compared to the distance between them. If it is impossible to neglect the sizes of bodies, then the bodies should be divided into point elements, according to formula (1), calculate the forces of attraction between all pairs taken elements and then decay geometrically. The tension of the gravitational field of the system consisting of material points with M 1, M 2, ..., M N is equal to the sum of the field strengths from each of these masses separately ( principle of superposition of gravitational fields ): g.=g. i. where g. i. \u003d (GM I / R i 2) r. o I. - the intensity of the field of one mass M i.

Gravitational field graphic image using tension vectors g. At various points, the fields are very uncomfortable: for systems consisting of many material points, tension vector are superimposed on each other and it turns out a very confusing picture. therefore for graphic image of the gravitational field use power lines (voltage lines), which are carried out in such a way that the tension vector is aimed at tangent to the power line. Tension lines are considered directed just like vector g.(Fig.1c), those. Power lines ends on a material point. Since every point of the space, the vector of tension has only one direction.T. tension lines never intersect. For material point, the power lines are radial straight, included in the point (Fig. 1b).

To using tension lines, not only direction, but also the field strength value, these lines are carried out with a certain dense: the number of tension lines that permeate the surface area of \u200b\u200bthe surface area, perpendicular to the tension lines, should be equal to the module vector g..

Each person in his life more than once came across this concept, because gravity is the basis of not only modern physics, but also a number of other related sciences.

Many scientists with ancient times were engaged in studying the tel, but the main discovery is attributed to Newton and is described as known to everyone with a fruit falling on his head.

What is gravity with simple words

Gravity is an attraction between several items throughout the universe. The nature of the phenomenon is different, as it is determined by the mass of each of them and the length between, that is, the distance.

Newton's theory was founded on the fact that both the falling fruit, and the same force acts on our planet's satellite - attraction to Earth. And did not fall satellite on earthly space because of its mass and remoteness.

Gravitational field

The gravitational field is space, within which the bodies interact under the laws of attraction takes place.

Einstein theory of relativity describes the field as a certain property of time and space, characterized by the appearance of physical objects.

Gravitational wave

This is a certain kind of field changes, which are formed as a result of radiation from moving objects. They come off from the subject and apply to the wave effect.

Gravity theory

The classic theory is Newtonian. However, it was imperfect and subsequently appeared alternative options.

These include:

• metric theories;
• nonmetric;
• vector;
• Le-soot, which first described the phases;
• quantum gravity.

Today there are several dozen different theories, they all either complement each other or consider phenomena on the other side.

It is worth noting: There is no ideal option yet, but constant development opens more options for answers regarding tel.

Power of gravitational attraction

The basic calculation is as follows - the force of gravity is proportional to the multiplication of body weight to another, between which it is determined. This formula is also pronounced: the force is inversely proportional to the distance between the objects raised to the square.

The gravitational field is potentially, and therefore persists kinetic energy. This fact simplifies the solution to the tasks in which the force of attraction is measured.

Gravity in space

Despite the delusion of many, there is gravity in space. It is lower than on earth, but still present.

As for the cosmonauts, which at first glance fly, they actually are in a state of slow fall. Visually, it seems that they do not attract anything, but in practice they are experiencing gravity.

The force of attraction depends on the remoteness, but no matter how big the distance between the objects, they will continue to reach each other. Mutual attraction will never be zero.

Gravity in the Solar System

In the solar system, not only the earth has gravity. Planets, as well as the sun, attract objects to themselves.

Since the force is determined by the mass of the subject, the greatest indicator at the Sun. For example, if our planet is equal to one, then the luminous indicator will be almost equal to twenty-eight.

The next, after the Sun, in gravity is Jupiter, so the force of attraction is three times higher than that of the Earth. The smallest parameter at Pluto.

For clarity, we will be denoted in the theory of the Sun, the average person weighing about two tons, but on the very small planet of our system - only four kilograms.

From which the gravity of the planet depends

Gravitational traction, as already mentioned above, is the power with which the planet pulls the items located on its surface.

The force of attraction depends on the severity of the object, the planet itself and the distance between them. If a lot of kilometers - gravity is low, but it still holds objects in touch.

Several important and fascinating aspects associated with gravity and its properties that should be explained by the child:

1. The phenomenon attracts everything, but never repels - it distinguishes it from other physical phenomena.
2. There is no zero indicator. It is impossible to simulate the situation in which the pressure does not work, that is, gravity does not work.
3. The land falls at an average rate of 11.2 kilometers per second, reaching this speed, you can leave the attracting well of the planet.
4. The fact of the existence of gravitational waves was not proved scientifically, it is only a guessed. If ever they become visible, Many cosmos puzzles will open with humanity related to the interaction of tel.

In accordance with the theory of basic relativity of such a scientist as Einstein, gravity is the curvature of the basic parameters of the existence of a material world, which is the basis of the Universe.

Gravity is the mutual attraction of two objects. The strength of the interaction depends on the severity of the bodies and the distance between them. So far, not all the secrets of the phenomenon are disclosed, but today there are several dozen theories describing the concept and properties.

The complexity of the objects studied affects the study. In most cases, the dependence of the mass and distance is simply taken.

Don Deng.

The power of gravity (or gravity) is firmly holding us on the ground and allows the earth to rotate around the sun. Thanks to this invisible strength, the rain falls to the ground, and the water level in the ocean is increasing every day, it decreases. Gravity keeps the Earth in spherical form, and also does not give our atmosphere to disappear into outer space. It would seem that this observed force of attraction should be well studied by scientists. But no! In many ways, gravity remains the deepest mystery for science. This mysterious force is a wonderful example of how much modern scientific knowledge is limited.

What is gravity?

Isaac Newton was interested in this issue back in 1686 and came to the conclusion that gravity is the force of attraction that exists between all objects. He realized that the same strength that causes the apple to fall on the ground, in his orbit. In fact, the force of attraction of the Earth is the reason that during rotation around the Earth, the moon deviates every second from its direct path about one millimeter (Figure 1). The universal law of the Newton gravity is one of the largest scientific discoveries of all times.

Gravity - "Rope" that holds objects in orbit

Picture 1.Illustration of the moon orbit, made not in accordance with the scale. Over a second, the moon runs about 1 km. For this distance, it deviates from the direct path of about 1 mm - this is due to the gravitational traction of the Earth (dotted line). The moon constantly seems to fall behind (or around) the earth, as the planets fall around the sun.

The force of gravity is one of the four fundamental forces of nature (Table 1). Pay attention to the fact that from four forces this power is the weakest, and yet it is dominant relative to major space objects. As Newton showed, the attractive gravitational force between two any masses is becoming less and less as the distance between them is becoming more and more, but it never fully reaches zero (see the "intelligence plan").

Therefore, each particle in the whole universe actually attracts any other particle. In contrast to the forces of weak and strong nuclear interaction, the attraction force is long-range (Table 1). Magnetic force and power electric interaction Also are long-appropriate forces, but the gravity is unique in that it and the long-range and always attractive, and therefore it can never dry out (in contrast to electromagnetism, in which the forces can either attract or repel).

Starting from the great scientist-creationist Michael Faraday in 1849, physicists constantly searched for a hidden connection between the power of attraction and power of electromagnetic interaction. Currently, scientists are trying to connect all four fundamental forces In one equation or the so-called "theory of all", but, unsuccessfully! Gravity remains the most mysterious and least studied force.

Gravity can not be protected in any way. Whatever the composition of the blocking partition, it does not have any effect on the attraction between the two separated objects. This means that in laboratory conditions it is impossible to create an antigravitational chamber. Gravity does not depend on chemical composition objects, but depends on their mass known to us as weight (the weight of gravity on the object is equal to the weight of this object - more MassaThe greater the power or weight.) Blocks consisting of glass, lead, ice, or even the eraphoma, and having the same mass, will experience (and render) the same gravitational force. These data were obtained during the experiments, and scientists still do not know how they can be theoretically explained.

Confusion in gravity

The force F between the two masses M 1 and M 2, which can be recorded in the formula F \u003d (G M 1 m 2) / R 2

Where G is a gravitational constant, first measured Henry Cavendis in 1798.1

This equation shows that gravity decreases as the distance, R, between two objects becomes larger, but completely never reaches zero.

The subject of this equation simply captures the subject of reverse squares. In the end, there is no necessary reason why the attraction force should act exactly. In the random, random and evolving universe, such random degrees as R 1.97 or R 2.3 would seem more likely. However, accurate measurements showed an accurate degree of at least up to five decimal discharges, 2.00000. As one researcher said, this result seems "Too accurate".2 We can conclude that the strength of attraction indicates the exact, created design. In fact, if the degree at least a little dismissed from 2, the orbits of the planets and the whole universe would be unstable.

Links and Notes

1. Speaking by technical language, G \u003d 6.672 x 10 -11 NM 2 KG -2
2. Tompsen, D., "very accurately about gravity", Science News. 118(1):13, 1980.

So what is in reality gravity? How can this power act in such a huge, empty outer space? And why does she exist at all? Science never managed to respond to these basic questions about the laws of nature. The force of attraction cannot appear slowly by mutations or natural selection. It acts from the very beginning of the existence of the universe. Like any other physical law, gravity is undoubtedly a wonderful testimony of planned creation.

Some scientists tried to explain gravity with invisible particles, gravitons, which move between objects. Others talked about cosmic strings and gravitational waves. Recently, scientists with the help of a specially created LIGO laboratory (Eng. Laser Interferometer Gravitational-Wave Observatory) managed only to see the effect of gravitational waves. But the nature of these waves, how physically objects interact with each other at huge distances, changing their odds, still remains for all the big question. We simply do not know the nature of the occurrence of gravity strength and how she keeps the stability of the whole universe.

Power of attraction and writing

Two places from the Bible can help us understand the nature of gravity and physical science generally. First place, Colossians 1:17, explains that Christ "There are first of all, and everything is worth it.". Greek verb costs (συνισταω sunistao.) Means: Clutch, persist or hold together. Greek use of this word outside the Bible denotes vessel with water contained in it. The word that is used in the Colossian Book is in perfect time, which as a rule, indicates the present continued state, which originated from the completed past action. One of the physical mechanisms used, which is clearly in question, is clearly the strength of attraction, installed by the Creator and unmistakably supported today. Just imagine: if the force of attraction ceased for a moment, chaos would undoubtedly come. All celestial bodies, including land, moon and stars, would not be held more together. All that hour would be divided into separate, small parts.

The second place of Scripture, Jews 1: 3, declares that Christ "Holds all the word power of his." Word holds (φερω pherō.) Describes the maintenance or preservation of everything, including gravity. Word holdsused in this verse means much more than just holding weight. It includes control over all the motions and changes inside the universe. This infinite task is performed through the Almighty word of the Lord, through which the Universe itself began to exist. Gravity, "mysterious power", which, and after four hundred years of research, remains poorly studied, is one of the manifestations of this amazing divine care of the universe.

Distortion of time and space and black holes

The general theory of Einstein's relativity considers gravity not as power, but as the curvature of the very space near the massive object. According to predictions, the light that traditionally follows direct lines is curved during the passage of the curved space. For the first time it was demonstrated when Astronomer Sir Arthur Eddington found a change in the apparent star position during full eclipse In 1919, believing that the rays of the light bend under the action of the gravity of the sun.

The general theory of relativity also predicts that if the body is quite dense, its gravity will distort the space so much that the light will not be able to pass through it at all. Such a body absorbs the light and everything else that captured its strong gravity, and is called a black hole. Such a body can be detected only by its gravitational effects on other objects, by strong curvature of light around it and by severe radiation emitted by the substance that falls on it.

All substance inside the black hole is compressed in the center, which has an infinite density. The "size" of the hole is determined by the horizon of events, i.e. The border that surrounds the center of the black hole, and nothing (even light) cannot go beyond its limits. The hole radius is called the Schwarzschald radius, in honor of the German astronomer Karl Schwarzschild (1873-1916), and is calculated by the formula R s \u003d 2gm / c 2, where C is the speed of light in vacuo. If the sun fell into a black hole, his Schwarzschald radius would be only 3 km away.

There is a reliable proof that after the core fuel of a massive star runs out, it can no longer withstand the collapse under its own huge weight and falls into a black hole. It is believed that black holes with a lot of billions of Suns exist in galaxic centers, including our galaxy, the Milky Way. Many scientists believe that superyar and very remote objects called the quasars, use energy that stands out when the substance falls into a black hole.

According to the predictions of the general theory of relativity, the strength of gravity also distorts the time. It was also confirmed by very accurate atomic clocks, which at the sea level go to several microseconds slower than in the territories above the sea level, where the strength of the ground is slightly weaker. Near the event horizon, this phenomenon is more noticeable. If you observe an astronaut's clock, which is approaching the horizon of events, we will see that the clock is slower. Being in the event horizon, the clock will stop, but we will never be able to see it. And on the contrary, the astronaut will not notic that his clock go slower, but he will see that our clocks go faster and faster.

The main danger to astronaut near the black hole would be tidal forcescaused by the fact that gravity is stronger on those parts of the body that are closer to the black hole than in parts further from it. In their power, the tidal forces near the black hole having a lot of stars, stronger than any hurricane and easily tear into small pieces, everything that came across. However, while gravitational attraction It decreases with the square of the distance (1 / R 2), the tidal and tidy phenomenon decreases with the distance cube (1 / R 3). Therefore, in contrast to the received opinion, the gravitational force (including tidal strength) on the horizons of the events of large black holes is weaker than on small black holes. So tidal forces on the horizon of black hole events in the observed space, would be less noticeable than the mild breeze.

Time stretching under the action of gravity near the horizon of events is the basis of the new cosmological model of the creator-creationist, Dr. Russell Humphres, about which he tells in his book "Light Star and Time". This model may help solve the problem of how we can see the light of remote stars in the young universe. In addition, today it is a scientific alternative to non-biblical, which is based on philosophical assumptions leaving for science.

Note

Gravity, "mysterious power", which, and after four hundred years of research, remains poorly studied ...

Isaac Newton (1642-1727)

Photo: Wikipedia.org.

Isaac Newton (1642-1727)

Isaac Newton published his discoveries about gravity and the movement of heavenly bodies in 1687, in his well-known work " Mathematical principles" Some readers quickly concluded that Newton's universe did not leave places for God, since everyone can now be explained by equations. But Newton did not think so at all, what he said in the second edition of this famous work:

"Our most beautiful solar system, planets and comets can only be the result of a plan and domination of a reasonable and strong creature. "

Isaac Newton was not only a scientist. In addition to science, he devoted almost all his life to the study of the Bible. His favorite biblical books were: the book of Daniel and the Book of Revelation, which describe God's plans for the future. In fact, Newton wrote more theological works than scientific.

Newton respectively belonged to other scientists, such as Galileo Galilee. By the way, Newton was born at the same year when Galilee died, in 1642. Newton wrote in his letter: "If I saw on others, then because it was standing on shoulders Giants. " Shortly before death, probably, reflecting on the secret of gravity, Newton wrote modestly: "I don't know how the world perceives me, but I myself seem only to a boy playing on the sea shore, which is having fun, that from time to time, it seeks pebbles more motley than others, or a beautiful shell, while in front of me is extruded Ocean unexplored truth. "

Newton is buried in Westminster Abbey. Latin inscription on his grave ends with the words: "Let the mortals rejoice that there was such a decoration of the human race among them".

What kind of law are you going to hang me?
- And we hinder everyone according to one law - the law of global.

The Law of the World Health

The phenomenon of gravity is the law of global gravity. Two bodies act on each other with force, which is inversely proportional to the square of the distance between them and is directly proportional to the product of their masses.

Mathematically we can express this great law formula

Communication acts at huge distances in the universe. But Newton argued that all objects are mutually attracted. Is it true that any two subjects attract each other? Just imagine, it is known that the earth attracts you sitting on a chair. But did they think about the fact that the computer and the mouse attract each other? Or pencil and handle lying on the table? In this case, in the formula we substitute a mass of the handle, a mass of a pencil, divided by a square of the distance between them, taking into account the gravitational constant, we obtain the power of their mutual attraction. But, it will come out on so much (because of the small masses of the handle and pencil) that we do not feel it. Another thing when it comes to earth and chair, or sun and earth. Mass are significant, which means the effect of force we can already evaluate.

Recall the acceleration of free fall. This is the action of the law of attraction. Under the action of strength, the body changes the speed of the slower than the more weight. As a result, all bodies fall on the ground with the same acceleration.

What caused this invisible unique force? To date, the existence of the gravitational field is also proved. Learn more about the nature of the gravitational field can be in additional material Topics.

Think about what kind of grade? Where is it from? What does it represent? After all, it can not be that the planet looks at the sun, sees how removed it is counting the reverse square of the distance in accordance with this law?

The direction of the force of attraction

There are two bodies, let the body A and V. Body attracts the body of V. The force with which the body is acting, begins on the body B and is directed towards the body A. That is, as it were, "takes" the body B and pulls to himself. The body in "doing" the same with the body A.

Each body is attracted by the Earth. The land "takes" the body and pulls to his center. Therefore, this force will always be directed vertically down, and it is attached from the center of gravity of the body, they call it strength.

The main thing is to remember

Some methods of geological exploration, prediction of tides and recently the calculation of the movement artificial satellites and interplanetary stations. Advanced calculation of the position of the planets.

Can we put such experience ourselves, and not to guess, do the planets, items are attracted?

Such direct experience did Cavendish (Henry Cavendish (1731-1810) - English physicist and chemist) With the help of the device that is shown in the figure. The idea was to hang the rod with two balls on a very thin quartz thread and then bring two large lead balls to them. The attraction of the balls slightly twists the thread - slightly, because the forces of attraction between ordinary objects are very weak. With the help of such a device, Cavendish managed to directly measure the power, distance and magnitude of both masses and, therefore, determine permanent G..

A unique discovery of a constant gravity G, which characterizes the gravitational field in space, allowed to determine the mass of the Earth, the Sun and other celestial bodies. Therefore, Cavendish called his experience "Weighing the Earth."

Interestingly, various physics laws have some common features. Let us turn to the laws of electricity (the power of the Coulomb). The electrical forces are also inversely proportional to the square of the distance, but already between charges, and the idea is involuntarily arising that in this pattern lies deep meaning. Until now, anyone has managed to present a lot and electricity as two different manifestations of the same entity.

Strength and here it changes in inversely in the square of the distance, but the difference in the magnitude of the electric forces and forces is amazing. Trying to establish the common nature of the electricity and electricity, we discover such a superiority of the electric forces on the forces of grave that it is difficult to believe that those and the other and the same source. How can we say that one acts stronger than the other? After all, it all depends on what the mass and what is the charge. Correcting how much actually acts, you are not entitled to say: "Take a lot of such a value," because you choose it yourself. But if we take what nature itself offers us (its own numbers and measures that have nothing to do with our inches, years, with our measures), then we can compare. We will take an elementary charged particle, such, for example, as an electron. Two elementary particles, two electrons, due to electric charge Pull out each other with force, inversely proportional to the square of the distance between them, and due to the gravity, they are attracted to each other again with force, inversely proportional to the square of the distance.

Question: What is the relationship of the power to electrical strength? Communication refers to electrical repulsion, as a unit to a number with 42 zeros. This causes deepest perplexity. Where could this huge number come from?

People are looking for this huge coefficient in other phenomena of nature. They move all sorts of large numbers, and if you need a large number, why not take, say, the ratio of the diameter of the universe to the proton diameter - or surprisingly, this is also a number with 42 zeros. And so they say: maybe this coefficient is equal to the ratio of the proton diameter to the diameter of the universe? This is an interesting thought, but since the Universe gradually expands, constant gravity should change. Although this hypothesis is not yet refuted, we have no evidence in her favor. On the contrary, some evidence suggests that constant gravity has not changed in this way. This is a huge number to this day remains a mystery.

Einstein had to modify the laws of gravity in accordance with the principles of relativity. The first of these principles states that the distance x can not be overcome instantly, whereas according to Newton's theory, the forces act instantly. Einstein had to change Newton's laws. These changes, clarifications are very small. One of them consists of this: because the light has energy, the energy is equivalent to the mass, and all the masses are attracted, the light is also attracted and, it means, passing by the Sun, should deviate. So it really happens. The force of gravity is also slightly changed in the theory of Einstein. But this very minor change in the law is just enough to explain some apparent misunderstanding in the movement of Mercury.

Physical phenomena in the micrometer are subject to other laws rather than phenomena in the world of large scale. Question arises: How does the world of small scales manifest? A quantum gravity theory will be answered. But quantum theory Gravity is not yet. People have not yet succeeded in creating the theory of gravity fully agreed with quantum mechanical principles and with the principle of uncertainty.

In nature, there are various forces that characterize the interaction of tel. Consider the forces that are found in the mechanics.

Gravitational forces. Probably the very first force, the existence of which was aware of a person, was the force of attraction acting on the body by the Earth.

And many centuries were required to ensure that people realize that the strength of gravity acts between any bodies. And many centuries were required to ensure that people realize that the strength of gravity acts between any bodies. The first thing this fact understood the English physicist Newton. Analyzing the laws that are subject to the movement of the planets (the laws of Kepler), he came to the conclusion that the observed laws of movement of the planets can be performed only if the attraction force acts between them, directly proportional to their masses and inversely proportional to the square of the distance between them.

Newton formulated the Law of the World Health. Any two bodies are attracted to each other. The force of attraction between point bodies is directed in a straight line, which connects them, directly proportional to the masses of both and inversely proportional to the square square between them:

Under point bodies in this case, they understand the body, the dimensions of which are many times less than the distance between them.

Worldwide forces are called gravitational forces. The proportionality G is called the gravitational constant. Its value was determined experimentally: G \u003d 6.7 10¯¹¹ n m² / kg².

Power of gravity The acting near the ground surface is directed to its center and is calculated by the formula:

where G is acceleration free fall (G \u003d 9.8 m / s²).

The role of the force in wildlife is very significant, since the size, forms and proportions of living beings are largely dependent on its magnitude.

Body weight. Consider what happens when some load is put on a horizontal plane (support). At the first moment after the goods lowered, it begins to move down under the action of gravity (Fig. 8).

The plane begins and arises the power of elasticity (support reaction), directed upwards. After the strength of elasticity (FU) is equilibrated by gravity, the lowering of the body and the deflection of the support will stop.

The deflection of the support appeared under the influence of the body, therefore, on the side of the body on the support there is some force (P), which is called the weight of the body (Fig. 8, b). According to the third law of Newton, the body weight is equal in the magnitude of the strength of the support reaction and is directed in the opposite direction.

P \u003d - FY \u003d FLAY.

Weight body call the strength of P, with which the body acts on a fixed relatively horizontal support.

Since the strength of gravity (weight) is applied to the support, it is deformed and due to elasticity has opposition to the strength of gravity. The forces developed at the same time from the support are called the supports of the support by the reaction, and the very phenomenon of the development of the opposition - the reaction of support. According to the third law of Newton, the reaction force of the support is equal to the magnitude of the gravity of the body and is opposite to him in the direction.

If the person on the support moves with the acceleration of the links of his body, directed from the support, the support force of the support increases by the value of Ma, where M is the mass of the person, and the acceleration with which the links of his body move. These dynamic effects can be fixed using strain gauges (dynamograms).

Weight should not be confused with body weight. The body weight characterizes its inert properties and does not depend on the strength of gravity, no of acceleration with which it moves.

The body weight characterizes the strength with which it acts on the support and depends on both the strength of grave and the acceleration of the movement.

For example, on the moon the body weight is about 6 times less than body weight on Earth, the same in both cases is the same and determined by the amount of substance in the body.

In everyday life, sports, sports often indicate not in Newton (H), but in kilograms of power (kgf). The transition from one unit to the other is carried out by the formula: 1 kgf \u003d 9.8 N.

When the support and body are fixed, the body mass is equal to the strength of the severity of this body. When the support and body move with some acceleration, depending on its direction the body may experience or weightlessness or overload. When acceleration coincides in the direction and equal to the acceleration of the free fall, the body weight will be zero, therefore the state of weightlessness occurs (ISS, high-speed elevator when lowering down). When the acceleration of the movement of the support is opposite to speeding up the free fall, the person experiences overload (start from the surface of the land of the pilotable spacecraft, High-speed elevator rising up).