What is the weight of a person in the air. Does air have weight? How much does a cube of air weigh

Although we do not feel the air around us, the air is not nothing. Air is a mixture of gases: nitrogen, oxygen and others. And gases, like other substances, are composed of molecules, and therefore have weight, albeit small.

Experience can prove that air has weight. In the middle of a stick sixty centimeters long, we will strengthen the rope, and we will tie two identical balloons to both ends of it. Let's hang the stick by the string and see that it hangs horizontally. If you now pierce one of the inflated balloons with a needle, air will come out of it, and the end of the stick to which it was tied will rise up. If you pierce the second ball, then the stick will again take a horizontal position.

This is because the air in the inflated balloon denser, which means that heavier than the one around it.

How much air weighs depends on when and where it is weighed. The weight of air above a horizontal plane is Atmosphere pressure. Like all objects around us, air is also subject to gravity. This is what gives the air a weight that is equal to 1 kg per square centimeter. The density of air is about 1.2 kg / m 3, that is, a cube with a side of 1 m, filled with air, weighs 1.2 kg.

An air column rising vertically above the Earth stretches for several hundred kilometers. This means that a column of air weighing about 250 kg presses on a person standing straight, on his head and shoulders, the area of ​​\u200b\u200bwhich is approximately 250 cm 2!

We would not be able to withstand such a weight if it were not opposed by the same pressure inside our body. The following experience will help us understand this. If you stretch a paper sheet with both hands and someone presses a finger on it from one side, then the result will be the same - a hole in the paper. But if you press with two index fingers on the same place, but with different parties, nothing will happen. The pressure on both sides will be the same. The same thing happens with the pressure of the air column and the counter pressure inside our body: they are equal.

By the way...

In everyday life, when we weigh something, we do it in air, and therefore we neglect its weight, since the weight of air in air is zero. For example, if we weigh an empty glass flask, we will consider the result obtained as the weight of the flask, neglecting the fact that it is filled with air. But if the flask is closed hermetically and all the air is pumped out of it, we will get a completely different result ...

Since gases have weight, the atmosphere, due to the force of the earth's gravity, does not dissipate in world space, but, enveloping the Earth, rotates with it. For every square meter at sea level, the mass of air exerts a pressure equal to 10333 kg. In other words, how much does a column of air with a cross section of 1 m 2 and height from ocean level to the top of the atmosphere. Weight 1 m 3 air at ocean level is about 1.03kg,

At the bottom of the air ocean, invisible, but felt by us, air presses on every square centimeter of area with a force equal to 1033 G. What is the pressure on our body? Obviously, if the outer surface of the human body averages about 12,000-15,000 s m 2, then the air pressure on it will be approximately 12,000-15,000 kg, or 12-15 t. However, the body does not feel this heaviness, since external pressure air is balanced by its pressure inside the body. Life on Earth is adapted to this pressure. Therefore, when climbing to high altitudes, a person's well-being deteriorates not only due to a lack of oxygen, but also due to a significant decrease in the pressure of a rarefied medium.

By the way, experiments in the pressure chamber showed that the more complex the organism, the more difficult it is to endure low air pressure. For example, a representative of cold-blooded animals is a frog at a height of 20-30 km saves life for several hours, and a person with a quick rise to a height of 7-8 km loses consciousness usually 8-10 minutes after getting up. At heights 15-16 km, even if a person breathes only oxygen, due to low pressure, oxygen starvation occurs within a few seconds. At low atmospheric pressure, the blood begins to boil. It is known that the lower the pressure, the faster the water boils. In the mountains, for example, water does not boil at 100°C, but at a lower temperature. At about 20 km water boils at a temperature of 37° above zero. The blood also boils at this altitude. Therefore, in space flight, a person is provided with appropriate physiological and hygienic conditions. In a pressurized cabin spaceship created normal pressure and more or less constant air temperature, the astronaut is protected from noise and vibrations, provided with a comfortable workplace, good lighting, etc.

Air pressure is measured in millimeters of mercury using a mercury or metal barometer. Pressure is usually expressed in thousandths of a bar, that is, in millibars. The mean pressure at sea level, expressed in millibars, is 1013.3. Air pressure 1000 mb equivalent to 750.1 mercury column pressure mm. To convert millimeters to millibars, the conversion factor 4 / s is usually used (Table 1).

As air density decreases with height, atmospheric pressure also decreases rapidly. Therefore, despite the large vertical extent of the atmosphere, half of its mass is concentrated in the first 5-6 km. The pressure at this level is only 500 mb, i.e. half as much as at sea level. In a column of air about 16 km concentrated 0.9 total

masses of the atmosphere. The pressure at this level is 100 mb, and at a height of 40 km - only 2.4mb.

The decrease in atmospheric pressure with height can be characterized by a vertical pressure gradient, or the so-called baric step. baric stage is the vertical distance (in meters) over which atmospheric pressure changes by one unit (by 1 mb). The value of the baric step is different. It depends on the altitude above sea level and on the air temperature. In the surface layer at a pressure of 1000 mb and a temperature of 0° the baric step is 8 m. This means that for every 8 m rise, the pressure decreases by 1 mb. In a layer with a pressure of 600-500 mb, which corresponds to heights of about 4.5-5.5 km, baric level is 13 m, in a layer with a pressure of 100-200 mb- 40 m.

The value of the baric step is convenient to use for approximate calculations of the change in pressure with height. So, for example, it is easy to determine the difference between air pressure on the 1st and 25th floors of a high-rise building. When the height difference of the indicated floors is 90 m, air pressure at the level of the 25th floor by about 12 mb less than at the level of the 1st floor. However, going up even on a high-speed elevator, we do not feel the difference in pressure. This is explained by the fact that the pressure change is about 10-20 mb very little (1-2%) compared to normal atmospheric pressure. The average daily change in pressure to which the human body is accustomed is small. In tropical countries, it is about 1 mb, and in middle latitudes - 5-6 mb. But in some, not very rare cases, the daily change in pressure in the middle latitudes reaches 20-30 mb and more.

Air is an intangible quantity, it is impossible to feel it, smell it, it is everywhere, but for a person it is invisible, it is not easy to find out how much air weighs, but it is possible. If the surface of the Earth, as in a children's game, is drawn into small squares, 1x1 cm in size, then the weight of each of them will be 1 kg, that is, 1 cm 2 of the atmosphere contains 1 kg of air.

Can it be proven? Quite. If you build a scale from an ordinary pencil and two balloons, fixing the structure on a thread, the pencil will be in balance, since the weight of the two inflated balls is the same. It is worth piercing one of the balls, the advantage will be in the direction of the inflated ball, because the air from the damaged ball has come out. Accordingly, simple physical experience proves that air has a certain weight. But, if we weigh the air on a flat surface and in the mountains, then its mass will be different - the mountain air is much lighter than the one we breathe near the sea. There are several reasons for different weights:

The weight of 1 m 3 of air is 1.29 kg.

• the higher the air rises, the more rarefied it becomes, that is, high in the mountains, the air pressure will not be 1 kg per cm 2, but half as much, but the content of oxygen necessary for breathing also decreases exactly by half, which can cause dizziness, nausea and ear pain;
• water content in the air.

The composition of the air mixture includes:

1. Nitrogen - 75.5%;

2. Oxygen - 23.15%;

3. Argon - 1.292%;

4. Carbon dioxide - 0.046%;

5. Neon - 0.0014%;

6. Methane - 0.000084%;

7. Helium - 0.000073%;

8. Krypton - 0.003%;

9. Hydrogen - 0.00008%;

10. Xenon - 0.00004%.

The number of ingredients in the composition of air can change and, accordingly, the mass of air also undergoes changes in the direction of increase or decrease.

• Air always contains water vapor. The physical pattern is that the higher the air temperature, the more water it contains. This indicator is called air humidity and affects its weight.

How is the weight of air measured? There are several indicators that determine its mass.

How much does a cube of air weigh?

At a temperature equal to 0 ° Celsius, the weight of 1 m 3 of air is 1.29 kg. That is, if you mentally allocate a space in a room with a height, width and length equal to 1 m, then this air cube will contain exactly this amount of air.

If air has weight and weight that is palpable enough, why doesn't a person feel heaviness? Such physical phenomenon, as atmospheric pressure, implies that an air column weighing 250 kg presses on each inhabitant of the planet. The area of ​​the palm of an adult, on average, is 77 cm 2. That is, in accordance with physical laws, each of us holds 77 kg of air in the palm of our hand! This is equivalent to the fact that we constantly carry 5 pound weights in each hand. AT real life even a weightlifter cannot do this, however, each of us can easily cope with such a load, because atmospheric pressure presses from both sides, as from the outside human body, and from the inside, that is, the difference is ultimately equal to zero.

The properties of air are such that it affects the human body in different ways. High in the mountains, due to lack of oxygen, visual hallucinations occur in people, and at great depths, the combination of oxygen and nitrogen into a special mixture - “laughing gas” can create a feeling of euphoria and a feeling of weightlessness.

Knowing these physical quantities, it is possible to calculate the mass of the Earth's atmosphere - the amount of air that is held in near-Earth space by gravity. The upper boundary of the atmosphere ends at a height of 118 km, that is, knowing the weight of m 3 of air, you can divide the entire borrowed surface into air columns, with a base of 1x1m, and add up the resulting mass of such columns. Ultimately, it will be equal to 5.3 * 10 to the fifteenth degree of tons. The weight of the planet's air armor is quite large, but even it is only one millionth of the total mass. the globe. The Earth's atmosphere serves as a kind of buffer that keeps the Earth from unpleasant cosmic surprises. From solar storms alone that reach the surface of the planet, the atmosphere loses up to 100 thousand tons of its mass per year! Such an invisible and reliable shield is air.

How much does a liter of air weigh?

A person does not notice that he is constantly surrounded by transparent and almost invisible air. Is it possible to see this intangible element of the atmosphere? Visually, moving air masses is broadcast daily on a television screen - warm or cold front brings long-awaited warming or heavy snowfall.

What else do we know about air? Probably, the fact that it is vital for all living beings living on the planet. Every day a person inhales and exhales about 20 kg of air, a quarter of which is consumed by the brain.

The weight of air can be measured in different physical quantities, including liters. The weight of one liter of air will be equal to 1.2930 grams, at a pressure of 760 mm Hg. column and a temperature of 0°C. In addition to the usual gaseous state, air can also occur in liquid form. For the transition of a substance into a given state of aggregation, the impact of enormous pressure and very low temperatures. Astronomers suggest that there are planets whose surface is completely covered with liquid air.

The sources of oxygen necessary for human existence are the Amazon forests, which produce up to 20% of this important element on the entire planet.

Forests are truly the “green” lungs of the planet, without which human existence is simply impossible. Therefore alive houseplants in an apartment are not just an interior item, they purify the air in the room, the pollution of which is ten times higher than on the street.

Clean air has long become a shortage in megacities, the pollution of the atmosphere is so great that people are ready to buy clean air. For the first time, “air sellers” appeared in Japan. They produced and sold clean air in cans, and any Tokyo resident could open a can for dinner. the purest air and enjoy its fresh scent.

Air purity has a significant impact not only on human health, but also on animals. In polluted areas of equatorial waters, near populated areas, dozens of dolphins are dying. The reason for the death of mammals is a polluted atmosphere; in the autopsy of animals, the lungs of dolphins resemble the lungs of miners clogged with coal dust. The inhabitants of Antarctica - penguins - are also very sensitive to air pollution, if the air contains a large amount of harmful impurities, they begin to breathe heavily and intermittently.

For a person, air cleanliness is also very important, so after working in the office, doctors recommend taking daily one-hour walks in the park, forest, and outside the city. After such "air" therapy, vitality the body is restored and well-being improves significantly. The recipe for this free and effective medicine has been known since ancient times, many scientists and rulers considered daily walks in the fresh air to be a mandatory ritual.

For a modern urban dweller, air treatment is very relevant: a small portion of life-giving air, the weight of which is 1-2 kg, is a panacea for many modern ailments!