Purpose of the work: to prove the existence of atmospheric pressure. Purpose of the work: to prove the existence of atmospheric pressure. Devices and materials: Devices and materials: glass filled with water glass filled with water paper. paper. Doing work Doing work

Fill an ordinary glass to the brim with water. We cover it with a piece of paper as shown in the figure. Tightly covering it with your hand, turn the paper down. Carefully remove your hand, holding the glass by the bottom. Water does not pour out. Fill an ordinary glass to the brim with water. We cover it with a piece of paper as shown in the figure. Tightly covering it with your hand, turn the paper down. Carefully remove your hand, holding the glass by the bottom. Water does not pour out. This is because air pressure holds the water. Air pressure spreads equally in all directions (according to Pascal's law), which means that it also goes up. The paper only serves to keep the surface of the water perfectly flat. This is because air pressure holds the water. Air pressure spreads equally in all directions (according to Pascal's law), which means that it also goes up. The paper only serves to keep the surface of the water perfectly flat.

Glass experience. Take two glasses, a candle end, some newsprint, scissors. Put a lit candle end in one of the glasses. From several layers of newsprint, laid one on top of the other, cut out a circle with a diameter slightly larger than the outer edge of the glass. Then cut out the middle of the circle so that most of the opening of the glass remains open. After moistening the paper with water, we get an elastic gasket, which we put on the upper edge of the first glass. Let us carefully place the inverted second glass on this pad and press it against the paper so that the interior of both glasses is isolated from the outside air. The candle will soon go out. Now, holding the top glass with your hand, raise it. We will see that the bottom glass seems to stick to the top one and rises with it.

This happened because the fire heated the air contained in the lower glass, and, as we already know, the heated air expands and becomes lighter, so some of it came out of the glass. When we slowly approached the second glass to the first, part of the air contained in it also had time to heat up and went outside. This means that when both glasses were tightly pressed against each other, there was less air in them than before the start of the experiment. The candle went out as soon as all the oxygen contained in the glasses was used up. After the gases remaining inside the glass cooled, a rarefied space arose there, and the air pressure outside remained unchanged, so it pressed the glasses tightly against each other, and when we raised the top one, the bottom one rose with it. The glasses would be even more tightly pressed together if we could create a completely empty space inside them.

Conclusion: so we proved the existence of atmospheric pressure with the two experiments given above. Conclusion: so we proved the existence of atmospheric pressure with the two experiments given above. The work was done by Elena Vasilyeva and Kristina Vasilyeva The work was done by Elena Vasilyeva and Kristina Vasilyeva

The fact that the Earth is covered with an air shell called atmosphere, you learned in geography lessons, let's remember what you know about the atmosphere from the geography course? It is made up of gases. They completely fill the volume provided to them.

AT raises the question: why do the air molecules in the atmosphere, moving continuously and randomly, do not fly away into the world space? What keeps them near the surface of the Earth? What strength? Holding on to gravity! So the atmosphere has mass and weight?

And why doesn't the atmosphere "settle" on the Earth's surface? Because between air molecules there are forces not only of attraction, but also of repulsion. In addition, in order to leave the Earth, they must have a speed of at least 11.2 km / s, this is the second space velocity. Most molecules have a speed less than 11.2 km/s.

Experience 1. Take two rubber balls. One is inflated, the other is not. What's in an inflated balloon? Put both balls on the scales. An inflated balloon on one bowl, an deflated one on the other. What do we see? (The inflated balloon is heavier).

We found out that air, like any body on Earth, is affected by gravity, has mass, and, therefore, has weight.

Guys, stretch your arms forward with your palms up. What do you feel? Are you having a hard time? But air presses on your palms, and the mass of this air is equal to the mass of a KAMAZ truck loaded with bricks. That is about 10 tons! Scientists have calculated that a column of air presses on the area 1 cm 2 with such strength as a kettlebell in 1 kg 33 g.

Mass of air in 1m³ of air: at sea level - 1 kg 293g; at an altitude of 12 km - 310 g; at an altitude of 40 km - 4g.

Why don't we feel this weight?

How is the pressure exerted on the lower air layer by the upper layer transferred? Each layer of the atmosphere is under pressure from all the upper layers, and, consequently, the earth's surface and the bodies located on it are under pressure from the entire thickness of the air, or, as they usually say, experiencing atmospheric pressureenenie, and, according to Pascal's law, this pressure is transmitted equally in all directions.

What material is the atmosphere made of? From the air? And what does he represent? Air - a mixture of gases: 78% - nitrogen, 21% - oxygen, 1% - other gases (carbon, water vapor, argon, hydrogen ...) . We often forget that air has weight. Meanwhile, the air density at the Earth's surface at 0°C is 1.29 kg/m 3 . The fact that air does have weight was proven by Galileo. And Galileo's student Evangelista Torricelli suggested and was able to prove that air exerts pressure on all bodies on the surface of the Earth. This pressure is called atmospheric pressure.

Atmospheric pressure is the pressure exerted by the Earth's atmosphere on all objects on it..

This is modern theoretical knowledge, but how did you learn about atmospheric pressure in practice?

Assumptions about the existence of atmospheric pressure arose in the 17th century.

The experiments of the German physicist and burgomaster of Magdeburg, Otto von Guericke, gained great fame in his study. While somehow pumping air out of a thin-walled metal ball, Guericke suddenly saw how this ball was flattened. Reflecting on the cause of the accident, he realized that the flattening of the ball was due to the pressure of the surrounding air.

To prove the existence of atmospheric pressure, he conceived and carried out such an experiment.

On May 8, 1654, in the German city of Regensburg, in a very solemn atmosphere, many nobles gathered, headed by Emperor Ferdinand III. They all witnessed an amazing spectacle: 16 horses struggled to separate 2 attached copper hemispheres, which had diameters of about a meter. What connected them? Nothing! - air. However, 8 horses pulling in one direction and 8 in the other could not separate the hemispheres. So the mayor of Magdeburg, Otto von Guericke, showed everyone that air is not nothing at all and that it presses with considerable force on all bodies. (2 assistants)

By the way, all people have “Magdeburg hemispheres” - these are the heads of the femurs, which are held in the pelvic joint by atmospheric pressure.

Now we will repeat the experiment with the Magdeburg hemispheres and reveal its secret.

Experience 2. Let's take two glasses. Put a lit candle end in one of the glasses. Cut out from several layers of newsprint a ring with a diameter slightly larger than the outer edge of the glass. After moistening the paper with water, put it on the upper edge of the first glass. Carefully ( slowly) put an inverted second glass on this gasket and press it to the paper. The candle will soon go out. Now, holding the top glass with your hand, raise it. We will see that the bottom glass seems to stick to the top one and rises with it. Why did this happen? The fire heated the air contained in the lower glass, and, as we already know, the heated air expands and becomes lighter, so some of it left the glass. This means that when both glasses were tightly pressed against each other, there was less air in them than before the start of the experiment. The candle went out as soon as all the oxygen contained in the glasses was used up. After the gases remaining inside the glass cooled down, a rarefied space arose there, and the atmospheric pressure outside remained unchanged, so it pressed the glasses tightly against each other, and when we raised the upper one, the lower one rose with it. We see that the atmospheric pressure is high.

How to measure atmospheric pressure?

It is impossible to calculate atmospheric pressure using the formula for calculating the pressure of a liquid column. After all, for this it is necessary to know the density and height of a column of liquid or gas. But the atmosphere does not have a clear upper boundary, and the density of atmospheric air decreases with increasing altitude. Therefore, Torricelli proposed a completely different way to find atmospheric pressure.

Torricelli took a glass tube about one meter long, sealed at one end, poured mercury into this tube and lowered the open end of the tube into a bowl of mercury. Some of the mercury spilled into the bowl, but most of the mercury remained in the tube. From day to day, the level of mercury in the tube fluctuated slightly, now falling a little, then rising a little.

The pressure of mercury at the level of its surface is created by the weight of the mercury column in the tube, since there is no air above the mercury in the upper part of the tube (there is a vacuum, which is called the "Torricellian void"). It follows that the atmospheric pressure is equal to the pressure of the mercury column in the tube. By measuring the height of the mercury column, you can calculate the pressure that the mercury produces. It will be equal to atmospheric. If atmospheric pressure decreases, then the mercury column in the Torricelli tube decreases, and vice versa. Observing daily changes in the level of the mercury column, Torricelli noticed that it could rise and fall. Torricelli also associated these changes with changes in the weather.

At present, the pressure of the atmosphere is equal to the pressure of a column of mercury with a height 760 mm at a temperature of 0°C, it is customary to call normal atmospheric pressure, which corresponds 101 325 Pa.

760 mmHg Art. =101 325 Pa 1 mmHg Art. =133.3 Pa

If you attach a vertical scale to the Torricelli tube, you get the simplest device for measuring atmospheric pressure - mercury barometer .

But using a mercury barometer is not safe, as mercury vapor is poisonous. Subsequently, other devices for measuring atmospheric pressure were created, which you will learn in the course of the next lesson.

Atmospheric pressure, close to normal, is usually observed in areas at sea level. With increasing altitude (for example, in the mountains), the pressure decreases.

Torricelli's experiments interested many scientists - his contemporaries. When Pascal found out about them, he repeated them with different liquids (oil, wine and water).

Experience 3. If you make a hole in the cap of a water bottle, squeeze and release some water. What happens to the shape of the bottle? Why is it deformed? What needs to be done so that it straightens and the water begins to pour out again intensively?( as a result of a bottle puncture, atmospheric air began to enter the bottle and put pressure on the water; this is used in droppers when administering medicines).

This method of changing the pressure in the bottle is used by housewives in cooking when separating yolks from proteins. How?

Atmospheric pressure also explains the suction effect of a swamp or clay. When a person tries to pull his leg out of a swamp or clay, a rarefaction forms under it, and atmospheric pressure does not change. The overbalance of atmospheric pressure can reach 1000 N per foot of an adult.

Experience 4. How to get a coin with your hands from the bottom of a plate of water without wetting them? It is necessary to put a piece of potato with matches stuck in it or a candle in a plate with water and light it. Top with a glass. The burning stopped and the water collected in the glass and the coin can be freely taken from the dry plate. What caused the water to collect under the glass?

We have observed interesting phenomena that are caused by the action of atmospheric pressure. Where have you seen in life such devices, the action of which is based on the existence and change of atmospheric pressure?

Most people, remembering their school years, are sure that physics is a very boring subject. The course includes many tasks and formulas that will not be useful to anyone in later life. On the one hand, these statements are true, but, like any subject, physics has the other side of the coin. But not everyone discovers it for themselves.

A lot depends on the teacher.

Perhaps our education system is to blame for this, or maybe it's all about the teacher, who thinks only that he needs to reprimand the material approved from above, and does not seek to interest his students. Most of the time it's his fault. However, if the children are lucky, and the lesson will be taught by a teacher who loves his subject himself, then he will be able not only to interest the students, but also help them discover something new. As a result, it will lead to the fact that children will begin to attend such classes with pleasure. Of course, formulas are an integral part of this academic subject, there is no escape from this. But there are also positive aspects. Experiments are of particular interest to students. Here we will talk about this in more detail. We will look at some fun physics experiments that you can do with your child. It should be interesting not only to him, but also to you. It is likely that with the help of such activities you will instill in your child a genuine interest in learning, and "boring" physics will become his favorite subject. it is not difficult to carry out, this will require very few attributes, the main thing is that there is a desire. And, perhaps, then you can replace your child with a school teacher.

Consider some interesting experiments in physics for the little ones, because you need to start small.

paper fish

To conduct this experiment, we need to cut out a small fish from thick paper (you can use cardboard), the length of which should be 30-50 mm. We make a round hole in the middle with a diameter of about 10-15 mm. Next, from the side of the tail, we cut a narrow channel (width 3-4 mm) to a round hole. Then we pour water into the basin and carefully place our fish there so that one plane lies on the water, and the second remains dry. Now you need to drip oil into the round hole (you can use an oiler from a sewing machine or a bicycle). The oil, trying to spill over the surface of the water, will flow through the cut channel, and the fish, under the action of the oil flowing back, will swim forward.

Elephant and Pug

Let's continue to conduct entertaining experiments in physics with your child. We suggest that you introduce your baby to the concept of a lever and how it helps to facilitate a person’s work. For example, tell us that you can easily lift a heavy wardrobe or sofa with it. And for clarity, show an elementary experiment in physics using a lever. To do this, we need a ruler, a pencil and a couple of small toys, but always of different weights (that's why we called this experiment "Elephant and Pug"). We fasten our Elephant and Pug to different ends of the ruler using plasticine, or an ordinary thread (we just tie the toys). Now, if you put the ruler with the middle part on the pencil, then, of course, the elephant will pull, because it is heavier. But if you shift the pencil towards the elephant, then Pug will easily outweigh it. This is the principle of leverage. The ruler (lever) rests on the pencil - this place is the fulcrum. Next, the child should be told that this principle is used everywhere, it is the basis for the operation of a crane, a swing, and even scissors.

Home experience in physics with inertia

We will need a jar of water and a household net. It will not be a secret for anyone that if you turn an open jar over, the water will pour out of it. Let's try? Of course, for this it is better to go outside. We put the jar in the grid and begin to smoothly swing it, gradually increasing the amplitude, and as a result we make a full turn - one, two, three, and so on. Water does not pour out. Interesting? And now let's make the water pour up. To do this, take a tin can and make a hole in the bottom. We put it in the grid, fill it with water and begin to rotate. A stream shoots out of the hole. When the jar is in the lower position, this does not surprise anyone, but when it flies up, the fountain continues to beat in the same direction, and not a drop from the neck. That's it. All this can explain the principle of inertia. When the bank rotates, it tends to fly straight, but the grid does not let it go and makes it describe circles. Water also tends to fly by inertia, and in the case when we made a hole in the bottom, nothing prevents it from breaking out and moving in a straight line.

Box with a surprise

Now consider experiments in physics with displacement. You need to put a matchbox on the edge of the table and slowly move it. The moment it passes its middle mark, a fall will occur. That is, the mass of the part extended beyond the edge of the tabletop will exceed the weight of the remaining one, and the boxes will tip over. Now let's shift the center of mass, for example, put a metal nut inside (as close to the edge as possible). It remains to place the boxes in such a way that a small part of it remains on the table, and a large one hangs in the air. The fall will not happen. The essence of this experiment is that the entire mass is above the fulcrum. This principle is also used throughout. It is thanks to him that furniture, monuments, transport, and much more are in a stable position. By the way, the children's toy Roly-Vstanka is also built on the principle of shifting the center of mass.

So, let's continue to consider interesting experiments in physics, but let's move on to the next stage - for sixth grade students.

water carousel

We need an empty tin can, a hammer, a nail, a rope. We pierce a hole in the side wall at the very bottom with a nail and a hammer. Next, without pulling the nail out of the hole, bend it to the side. It is necessary that the hole be oblique. We repeat the procedure on the second side of the can - you need to make sure that the holes are opposite each other, but the nails are bent in different directions. We punch two more holes in the upper part of the vessel, we pass the ends of a rope or a thick thread through them. We hang the container and fill it with water. Two oblique fountains will start to beat from the lower holes, and the can will begin to rotate in the opposite direction. Space rockets work on this principle - the flame from the engine nozzles hits in one direction, and the rocket flies in the other.

Experiments in physics - Grade 7

Let's do an experiment with mass density and find out how you can make an egg float. Experiments in physics with different densities are best done on the example of fresh and salt water. Take a jar filled with hot water. We put an egg in it, and it immediately sinks. Next, add salt to the water and stir. The egg begins to float, and the more salt, the higher it will rise. This is because salt water has a higher density than fresh water. So, everyone knows that in the Dead Sea (its water is the most salty) it is almost impossible to drown. As you can see, experiments in physics can significantly increase the horizons of your child.

and a plastic bottle

Schoolchildren of the seventh grade begin to study atmospheric pressure and its effect on the objects around us. To reveal this topic more deeply, it is better to conduct appropriate experiments in physics. Atmospheric pressure affects us, although it remains invisible. Let's take an example with a balloon. Each of us can inflate it. Then we will put it in a plastic bottle, put the edges on the neck and fix it. Thus, air can only enter the ball, and the bottle becomes a sealed vessel. Now let's try to inflate the balloon. We will not succeed, since the atmospheric pressure in the bottle will not allow us to do this. When we blow, the balloon begins to displace the air in the vessel. And since our bottle is airtight, it has nowhere to go, and it begins to shrink, thereby becoming much denser than the air in the ball. Accordingly, the system is leveled, and it is impossible to inflate the balloon. Now we will make a hole in the bottom and try to inflate the balloon. In this case, there is no resistance, the displaced air leaves the bottle - atmospheric pressure equalizes.

Conclusion

As you can see, experiments in physics are not at all complicated and quite interesting. Try to interest your child - and studying for him will be completely different, he will begin to attend classes with pleasure, which will eventually affect his academic performance.

The first blow, most likely, led to the fact that the ruler simply fell off the table, rebounded, and remained intact. The second blow most likely broke it in two. If the second stroke fails, try again, making sure the newspaper is perfectly flat.

Why is this happening?

You managed to break the line with the second blow because atmospheric pressure helped you. When you spread the area of ​​the newspaper over the surface of the ruler, a wide "suction cup" was formed that did not allow air to "drain" down. When you hit the ruler with the edge of your hand, it tried to free itself from under the newspaper, but since the air could not “flow” down (into the space between the table and the newspaper) at a high speed, most of the air pushed down the newspaper, and with it and a ruler.

So, you had a twenty-centimeter ruler covered with newspaper. If it was 2.5 centimeters thick, then its area was 50 square centimeters. Do not forget about a hundred plus kilometers of air and a kilogram of pressure per square centimeter. As a result, when you hit, as many as 50 kilograms fell on the fragile ruler. The ruler "tried", as for the first time, to jump off the table, but was crushed by a fifty-kilogram mass.

In mountainous areas, the air cover is thinner. From more than a hundred, the height of the mountain on which the settlement is located should be taken away. But the air column remains gigantic even without the few percentage points by which it is reduced by the height of the mountain. This pressure is enough to press the ruler to the table. In fact, there are many fun experiments that demonstrate the incredible power of the earth's atmosphere. This is just one of them. But there is only one explanation: the air cover is incredibly heavy and in certain cases its strength can manifest itself in the most unexpected way. And this causes surprise, delight and a lot of other emotions for everyone who has had a chance to take a fresh look at the majestic power of nature.

Inspired by Education.com

Introduction

We hear about atmospheric pressure almost every day, for example, when we hear the weather forecast or a conversation between two grandmothers about pressure and a headache. The atmosphere surrounds us everywhere and crushes its weight, but we do not feel this pressure. How can you prove the existence of atmospheric pressure?

Hypothesis : if the atmosphere exerts pressure on us and the bodies around us, then it can be detected empirically.Target : experimentally prove the existence of atmospheric pressure.Tasks :

1. Select and conduct experiments proving the existence of atmospheric pressure.

2. Show the practical application of atmospheric pressure in everyday life, technology, nature.

An object : Atmosphere pressure.Subject : experiments proving the existence of atmospheric pressure.Methods research: analysis of literature and Internet materials, observation, physical experiment, analysis and generalization of the results obtained.Chapter 1. The concept of atmospheric pressure §1.From the history of the discovery of atmospheric pressure

Atmospheric pressure was first measured by the Italian scientist, mathematician and physicist Evangelisto Torricelli back in 1644. He took a glass tube 1 meter long, sealed at one end, filled it completely with mercury and turned it over, lowering the open end into a cup of mercury. To the surprise of others, only a small part of the mercury spilled out of the tube. A column of mercury 76 cm high (760 mm) remained in the tube. Torricelli argued that the column of mercury is held by atmospheric pressure. It was to him that the idea first came. Torricelli called his device a mercury barometer and proposed to measure atmospheric pressure in millimeters of mercury (Fig. 1).

Rice. 1 Torricelli mercury barometer Fig. 2 Water barometer

Since then, the name barometer appeared (from the Greek.

baros - heaviness,metreo - measure).

Atmospheric pressure was measured by the French scientist Blaise Pascal, after whom the unit of pressure is named. In 1646 he built a water barometer to measure atmospheric pressure. To measure atmospheric pressure of 760 mm Hg, the height of the water column in this barometer reached more than 10 meters, which, of course, is very inconvenient (Fig. 2).

Modern barometers are available to every inhabitant. Figure 3 shows a modern barometer - aneroid (translated from Greek -

aneroid ). The barometer is called so because it does not contain mercury.

Fig. 3. Barometer - aneroid

Many scientists tried to prove the existence of atmospheric pressure, conducted experiments. The 7th grade physics textbook describes an experiment that proves the existence of atmospheric pressure. In 1654, an experiment was carried out with the "Magdeburg hemispheres". Air was evacuated from tightly pressed metal hemispheres. Atmospheric pressure squeezed them so strongly from the outside that even 16 (eight pairs) of horses, pulling the hemispheres in different directions, could not separate the hemispheres again (Fig. 4). This experiment was carried out by a German physicist, mayor of the city of Magdeburg, Otto von Guericke.

Now in Germany, monuments to the famous "Magdeburg hemispheres" can be found at every step (Fig. 5).

Fig.4 Experiment with hemispheres Fig.5 "Magdeburg hemispheres"

§2 Features of atmospheric pressure

What is the mechanism of atmospheric pressure formation? We found the answer to this question in the textbooks of natural history, physics, and on the Internet.

The air envelope surrounding the Earth is called the atmosphere (from the Greek

atmosphere - steam, air,sphere - ball). The atmosphere extends to a height of several thousand kilometers and is similar to a multi-storey building (Fig. 6). As a result of the attraction of the Earth, the upper layers of the atmosphere press their weight on the lower layers. The air layer adjacent directly to the Earth is compressed the most and, according to Pascal's law, transfers pressure in all directions to everything that is on and near the Earth.

Fig.6 The structure of the Earth's atmosphere.

Observations of meteorologists show that the atmospheric pressure in areas above sea level is on average 760 mm Hg, this pressure is called

normal atmospheric pressure . As the altitude increases, the air density decreases, which leads to a decrease in pressure. At the top of a mountain, atmospheric pressure is less than at its foot. With small ascents, on average, for every 10.5 m of ascent, the pressure decreases by 1 mmHg or 1.33 hPa.

The existence of atmospheric pressure can be explained by many phenomena that we encounter in life. For example, I learned from a grade 7 physics textbook that as a result of atmospheric pressure, a force equal to 10N acts on every square centimeter of our body and any object, but the body does not collapse under the influence of such pressure. This is due to the fact that it is filled with air inside, the pressure of which is equal to the pressure of the outside air. When we inhale air, we increase the volume of the chest, while the air pressure inside the lungs decreases and atmospheric pressure pushes a portion of air there. When exhaling, the opposite happens.

How do we drink?

The inhalation of liquid by the mouth causes expansion of the chest and rarefaction of air, both in the lungs and in the mouth. The pressure inside the mouth decreases. Increased, in comparison with the internal, external atmospheric pressure "drives" part of the liquid there. How the human body uses atmospheric pressure.

The principles of operation of many devices are based on the phenomenon of atmospheric pressure. One of these is the piston liquid pump. The pump is schematically shown in Figure 7. It consists of a cylinder, inside which a piston tightly attached to the walls goes up and down. When the piston moves up, the water rises up (into the void) under the action of atmospheric pressure.

The medical syringe, which is widely used in medicine, works on the same principle.

It is curious that back in 1648, the French philosopher, mathematician and physicist Blaise Pascal, studying the behavior of a liquid under pressure, invented a syringe - a funny design from a press and a needle. The real syringe appeared only in 1853. It is curious that two people who worked independently of each other designed the injection machine at once: the Scotsman Alexander Wood (Wood) and the Frenchman Charles Gabriel Pravaz (Pravaz). And the name "spritze", which means "inject, splash", came up with the Germans.

Fig.7 Pump Fig.8 Hydraulic press and fountain

The action of atmospheric pressure explains the principle of operation of a hydraulic press, a jack, a hydraulic brake, a fountain, a pneumatic brake, and many technical devices (Fig. 8).

Changes in atmospheric pressure affect the weather.

With a decrease in atmospheric pressure, air humidity rises, precipitation and an increase in air temperature are possible. When atmospheric pressure rises, the weather becomes clear and does not have sudden changes in humidity and temperature.In order for a person to be comfortable, atmospheric pressure should be equal to 750 mm. rt. pillar.

If atmospheric pressure deviates, even by 10 mm, in one direction or another, a person feels uncomfortable and this may affect his state of health.

As a result of theoretical studies, we found that atmospheric pressure significantly affects human life.

Chapter 2. Experiments Confirming the Existence of Atmospheric Pressure Experience No. 1 . The principle of operation of a medical syringe and pipette . Devices and materials : syringe, pipette, glass of colored water.Experience progress : lower the plunger of the syringe down, then lower it into a glass of water and raise the plunger. The water will enter the syringe (Fig.9). We press on the rubber band of the pipette, the liquid enters the glass tube.Explanation of experience : When the plunger is lowered, air exits the syringe and the air pressure in it decreases. Outside air under the action of atmospheric pressure pushes the liquid into the syringe. The pipette “works” according to the same principle (Fig. 10).

Fig.9 Medical syringe 10 Pipette

Experience number 2. How to get a coin out of the water without getting your hands wet? Devices and materials : a plate, a candle on a stand, a dry glass.Experience progress : put a coin on a plate, then pour some water, put a lit candle. We cover the candle with a glass. The water is in the glass, and the plate is dry.Explanation of experience : the candle burns and the air from under the glass is rarefied, the air pressure there decreases. Atmospheric pressure outside pushes water under the glass.

Fig. 11 Experience with a coin

Experience number 3. The glass is non-spill. Devices and materials : glass, water, sheet of paper.Experience progress : pour water into a glass and cover with paper on top. Flip the glass. The sheet of paper does not fall, the water from the glass does not spill.Explanation of experience : air presses from all sides and from bottom to top too. Water acts on top of the leaf. The pressure of the water in the glass is equal to the pressure of the air outside.Experience number 4. How to put an egg in a bottle? Devices and materials : a glass bottle with a wide neck, a boiled egg, matches and candles for the cake.Experience progress : peel the boiled egg, stick the candles into the egg and set them on fire. We bring the bottle from above and insert the egg into it like a cork. The egg will be drawn into the bottle.Experience Explanation: the fire displaces the oxygen from the bottle, the air pressure inside the bottle has decreased. Outside, the air pressure remains the same and pushes the egg into the bottle (Fig. 12).

Rice. Fig. 12 Experiment with egg Fig. 13 Experiment with bottle

Experience No. 5. Flattened bottle. Devices and materials : hot water kettle, empty plastic bottle.Experience progress : Rinse the bottle with hot water. Drain the water and quickly close the bottle cap. The bottle will collapse.Explanation of experience : hot water heated the air in the bottle, the air expanded. When the bottle was corked, the air cooled. At the same time, the pressure decreased. Outside atmospheric air squeezed the bottle (Fig.13).

Experience number 6. A glass of water and a sheet of paper.

Devices and materials : a glass, water and a sheet of paper.

Experience progress : pour water into a glass (but not full), cover with a sheet of paper and turn over. The leaf will not fall off the glass.

Explanation of experience : a sheet of paper holds atmospheric pressure, which acts from the outside with a greater force than the weight of water in a glass. (Fig. 14)

Rice. 14 experience with a glass

Experience number 7. Otto von Guericke at home.

Devices and materials : 2 glasses, a ring of a sheet of paper with a diameter of a glass soaked in water, a candle end, matches.

Experience progress : put a lit candle in one glass, put a paper ring dipped in water on top and cover with a second glass and press lightly. The candle goes out, we raise the upper glass and notice that the second glass is pressed against the upper one.

Explanation of experience : the air expanded from heating and part of it came out. The less air remains inside, the more they are compressed from the outside by atmospheric pressure, which remains constant. Penetrate inside the air, prevents moistened with water, a paper ring

Fig.15 Magderburg hemispheres at home.

Chapter 3. Practical use of atmospheric pressure.

1. How do we drink? We put a glass or spoon with a liquid to our mouth and “draw” their contents into ourselves. Why, in fact, the liquid rushes into our mouths? What fascinates her? The reason is this: when we drink, we expand the chest and thereby rarefy the air in the mouth; under the pressure of the outside air, the liquid rushes towards us in the space where the pressure is less, and thus penetrates into our mouth.

So, strictly speaking, we drink not only with the mouth, but also with the lungs; because the expansion of the lungs is the reason that the fluid rushes into our mouth.

2. Atmospheric pressure in wildlife. Flies and tree frogs can stick to window glass thanks to tiny suction cups that create a vacuum and atmospheric

the pressure keeps the suction cup on the glass. Sticky fish have a suction surface consisting of folds that form deep "pockets".
When you try to tear the suction cup off the surface to which it is stuck, the depth of the pockets increases, the pressure in them decreases, and then the external pressure presses the suction cup even more strongly.

3.Automatic bird drinker consists of a bottle filled with water and overturned in the trough so that the neck is slightly below the level of the water in the trough. Why doesn't water pour out of the bottle? Atmospheric pressure keeps the water in the bottle.

4. Piston liquid pump The water in the cylinder rises behind the piston under the action of atmospheric pressure. The action of piston pumps is based on this. The pump is shown schematically in the figure. It consists of a cylinder, inside which piston 1, which is tightly attached to the walls, goes up and down. Valves 2 are installed in the lower part of the cylinder and in the piston itself, opening only upwards. When the piston moves upwards, water enters the pipe under the action of atmospheric pressure, lifts the bottom valve and moves behind the piston. (see appendix fig 1). When the piston moves down, the water under the piston presses on the bottom valve, and it closes. At the same time, a valve inside the piston opens under the pressure of the water, and the water flows into the space under the piston. With the subsequent upward movement of the piston, the water above it rises with it, which is poured into the pipe. At the same time, a new portion of water rises behind the piston, which, when the piston is subsequently lowered, will be above it.

5.Leaver This is a device for taking various liquids.. The liver is lowered into the liquid, then the upper hole is closed with a finger and removed from the liquid. When the upper hole is opened, water starts to flow from the liver

6. Aneroid barometer is an instrument for measuring atmospheric pressure based on a non-liquid design. The operation of the device is based on the measurement of elastic deformations caused by atmospheric pressure
thin-walled metal vessel from which air is pumped out.