And again I will allow myself to touch on old books, this time the two-volume “Entertaining Physics”. The author of this book, remarkable in all respects, is Yakov Isidorovich Perelman, who was the largest and most famous popularizer of science in the USSR.
He is the author of a whole galaxy of popular science books, of which “Entertaining Physics” is just the most famous. It has gone through more than 20 reprints (I can’t say for sure, but if it has been reprinted again recently, it will already be about 30 reprints). This two-volume book was wildly popular in the then Union and would now be called a bestseller.
I wanted to buy it for myself for a long time and it was finally acquired (this was several years ago, and I was looking for this two-volume book for years). It is written in a very simple and understandable language, and in order to understand this book, the knowledge of the school physics course for grades 7-9 is enough. Moreover, with the help of this book you can conduct a number of very instructive and serious experiments at home.
Plus, everything else, it examines in detail the most typical mistakes of science fiction writers specializing in science fiction (H.G. Wells and Jules Verne are especially beloved by the author), however, Yakov Isidorovich does not ignore other authors and other works. For example, take the same Mark Twain, who gave the world a lot of satirical works.
Let me just cite one of the paragraphs of this wonderful two-volume book?
"Barometer Soup"
In the book “Wanderings Abroad”, the American humorist Mark Twain talks about one incident of his Alpine travel - an incident, of course, fictitious:
Our troubles are over; therefore, people could relax, and I finally had the opportunity to pay attention to the scientific side of the expedition. First of all, I wanted to determine the altitude of the place where we were using a barometer, but, unfortunately, I did not get any results. From my scientific readings I knew that either a thermometer or a barometer must be boiled to obtain a reading. I didn’t know for sure which of the two, so I decided to boil both.
And yet I didn't get any results. Having examined both instruments, I saw that they were completely damaged: the barometer had only one copper needle, and a lump of mercury was dangling in the thermometer ball...
I found another barometer; it was completely new and very good. I boiled it for half an hour in a pot with bean soup, which the cook had prepared. The result was unexpected: the instrument stopped working, but the soup acquired such a strong barometer flavor that the head cook - a very smart man - changed its name in the list of dishes. The new dish earned everyone's approval, so I ordered barometer soup to be prepared every day. Of course, the barometer was completely ruined, but I didn’t particularly regret it. Since it didn’t help me determine the height of the area, it means I don’t need it anymore.
Jokes aside, let's try to answer the question: what really should have been “boiled”, a thermometer or a barometer?
Thermometer, and here's why.
From previous experience ( this fragment was removed from the main context, as I mentioned at the very beginning.— approx. mine) we have seen that the lower the pressure on water, the lower its boiling point. Since atmospheric pressure decreases with elevation in the mountains, the boiling point of water should also decrease. Indeed, the following boiling temperatures of pure water are observed at different atmospheric pressures:
| Boiling point, °C | Pressure, mmHg Art. |
| 101 | 787,7 |
| 100 | 760 |
| 98 | 707 |
| 96 | 657,5 |
| 94 | 611 |
| 92 | 567 |
| 90 | 525,5 |
| 88 | 487 |
| 86 | 450 |
In Bern (Switzerland), where the average atmospheric pressure is 713 mm Hg. Art., water in open vessels already boils at 97.5 ° C, and at the top of Mont Blanc, where the barometer shows 424 mm Hg. Art., boiling water has a temperature of only 84.5 ° C. For every kilometer rise, the boiling point of water drops by 3 °C. This means that if we measure the temperature at which water boils (as Twain put it, if we “boil the thermometer”), then by consulting the corresponding table, we can find out the height of the place. To do this, you must, of course, have pre-compiled tables at your disposal, which Mark Twain “simply” forgot about.
The instruments used for this purpose - hypsothermometers - are no less convenient to carry than metal barometers, and give much more accurate readings.
Of course, a barometer can also serve to determine the altitude of a place, since it directly, without any “boiling”, shows the pressure of the atmosphere: the higher we rise, the less pressure. But even here you need either tables showing how air pressure decreases as you rise above sea level, or knowledge of the corresponding formula. All this seemed to get mixed up in the comedian’s head and prompted him to “cook barometer soup.”
I wonder how many of my blog readers knew the answer before the end of the passage? And which of them remembers (knows) this mysterious formula mentioned in an excerpt from the book?
Yes, by the way, thanks to atmospheric pressure you can perform very interesting physical tricks. When I was a physics teacher at school, I showed schoolchildren a simple trick while studying the topic “atmospheric pressure”. He took a glass tube with two open ends, about 50 cm long. With the flattened (narrower) end, he placed the tube in a vessel with water and waited for water to fill the tube. Then he plugged the wider edge of the tube with his thumb, removed the tube from the vessel and turned it over. From the narrow edge of the tube, water flowed to a fairly decent height. Then, quietly replacing the vessel with water, I gave the schoolchildren the opportunity to repeat the trick, but they didn’t succeed. The inevitable “debriefing” began, at which the essence of this trick was revealed.
Have any of you already guessed what the catch was?
P.S. A gypsum thermometer is also known as a thermobarometer. Note that at pressure near atmospheric, a change in the boiling point of pure water by 0.1 °C corresponds to a change in atmospheric pressure by 2.5-3 mm Hg. Art. (or an equivalent change in terrain height of approximately 30 m). The scale of a modern thermobarometer is divided into hundredths of a degree or the corresponding units of pressure in mmHg. Art. The device, in addition to a thermometer with a scale, includes a boiler - a metal vessel with clean water and a heater. Despite its simplicity, the thermobarometer is a convenient and accurate instrument suitable for use in expeditionary conditions.
Place a metal bucket on the rotating circle. We lower a small container into it. Then pour flammable liquid or alcohol into the container. We light the liquid to ignite and begin to rotate the circle. We are watching a real tornado.
When the circle unwinds, the flame begins to rush upward and spins like a tornado. This happens because when the bucket rotates, it carries air along with it, and a certain vortex is formed inside, that is, a certain movement of air is formed there, and if the air has movement, then the pressure inside will be less according to Bernoulli’s law and begins to suck in air with all its force. surroundings. And he fans this fire, and since there is an upward flow, a flame is formed inside and due to the fact that the flow swirls, the air also swirls.
Fill the bottle 1/3 full with hot water. Carefully place the boiled, peeled egg on the neck of the bottle. Wait a few minutes and the egg will fall to the bottom of the bottle. When you pour hot water into a bottle, it and all the air in it heats up. The air outside is cooler. And while the air in the bottle and outside are different, hot air tends to leave the bottle as quickly as possible. Due to these actions, a pressure difference occurs, which subsequently causes the testicle to fall to the bottom of the bottle.
3. According to the size of the plywood board Cut a 10x10cm rubber pad from an old volleyball bladder and attach it to the plywood with thumbtacks. Pour a little water into a half-liter glass jar and a little alcohol onto the water. Light the alcohol. After letting it burn for a short time, close the jar with a board. The fire will go out. After 1-2 seconds, lift the board. Together with it, the can rises, into which the rubber has been drawn. How can we explain the lifting of the can with the board and the retraction of the rubber? Where is this phenomenon used in practice? When burning, the air heats up. After closing the can, the combustion process stops. The air begins to cool. A vacuum occurs in the can, due to which it is pressed against the plywood by atmospheric pressure. The retraction of rubber is also explained by atmospheric pressure. Treatment using medical cups is based on this phenomenon.
4. EXPERIMENT WITH GLASSES (Magdeburg hemispheres).
Cut a rubber or paper ring to fit the diameter of the cut glass and place it on the glass. Light a piece of paper or a small candle, place it in a glass and almost immediately cover it with a second glass. Through. Raise the top glass for 1-2 seconds, followed by the bottom one.
5. Spray bottle
Goal: learn how a spray gun works. You will need a glass, scissors, and two flexible straws. 
Pour water into a glass.
Cut one straw near the corrugated part and place it vertically in the glass so that it extends 1 cm out of the water with the corrugation.
Place the second straw so that its edge touches the top edge of the straw standing in the water. Use the corrugated folds on the vertical straw to support it.
Blow forcefully through a horizontal straw.
The water rises up the straw standing in the water and is sprayed into the air.
WHY? The faster the air moves, the greater the vacuum created. And since the air from the horizontal straw moves over the upper cut of the vertical straw, the pressure in it also drops. The atmospheric air pressure in the room presses on the water in the glass, and the water rises up the straw, from where it is blown out in the form of tiny droplets. When you press on the rubber bulb of the spray bottle, the same thing happens. The air from the bulb passes through the tube, the pressure in it drops, and because of this rarefaction of air, the cologne rises up and is sprayed.
6. Water does not pour out
7. As soon as the candle stops burning, the water in the glass rises.
Place the coin on a large flat plate. Pour in enough water to cover the coin. Now invite guests or spectators to take out the coin without getting their fingers wet. To carry out the experiment, you also need a glass and several matches stuck into a cork floating on the water. Light matches and quickly cover the floating burning boat with a glass, without taking the coins. When the matches go out, the glass will fill with white smoke, and then all the water from the plate will collect under it. The coin will stay in place and you can pick it up without getting your fingers wet.
Explanation. The force that drives water under the glass and holds it there at a certain height is atmospheric pressure. The burning matches heated the air in the glass, its pressure increased, and some of the gas came out. When the matches went out, the air cooled down again, but as it cooled, its pressure decreased and water entered under the glass, driven there by the pressure of the outside air.
9. How does it work Diving bell.
Experiment 1. Take a plunger, which is used in plumbing, moisten its edges with water and press it to the suitcase, which is placed on the table. Squeeze some of the air out of the plunger and then lift it up. Why does the suitcase rise with him? In the process of pressing the plunger against the suitcase, we reduce the volume occupied by the air, and some of it comes out from under the plunger. When the pressure stops, the plunger expands and a vacuum forms under it. External atmospheric pressure presses the plunger and the suitcase against each other.
Experiment 2. Press the plunger to the chalkboard, hang a load weighing 5-10 kg from it. The plunger is held on the board along with the load. Why?
11. Automatic bird drinker.An automatic bird drinker consists of a bottle filled with water and tipped into a trough so that the neck is slightly below the water level in the trough. Why doesn't water pour out of the bottle? If the water level in the trough drops and the neck of the bottle comes out of the water, some of the water will spill out of the bottle.
12. How we drink. Take two straws, one whole, and make a small hole in the second. Through the first, water enters the mouth, but not through the second. 13. If you pump air out of a funnel whose wide opening is covered with a rubber film, the film is drawn in and then even bursts.Inside the funnel, the pressure decreases; under the influence of atmospheric pressure, the film is drawn inward. This can explain the following phenomenon: If you put a maple leaf to your lips and quickly draw in air, the leaf will burst with a crash. 
Equipment: strip 50-70 cm long, newspaper, meter.
Conduct: Place a slate on the table and a fully unrolled newspaper on it. If you slowly apply pressure to the hanging end of the ruler, it goes down, and the opposite one rises along with the newspaper. If you sharply hit the end of the rail with a meter or a hammer, it breaks, and the opposite end with the newspaper does not even rise. How to explain this?
Explanation: Atmospheric air exerts pressure on the newspaper from above. By slowly pressing on the end of the ruler, air penetrates under the newspaper and partially balances the pressure on it. With a sharp impact, due to inertia, the air does not have time to instantly penetrate under the newspaper. The air pressure on the newspaper from above is greater than from below, and the rail breaks.
Notes: The rail should be placed so that its end hangs 10 cm. The newspaper should fit snugly against the rail and table.
15. Entertaining experiments with atmospheric phenomena
SELF-OSCILLATIONS
Mechanical oscillatory motion is usually studied by considering the behavior of some kind of pendulum: spring, mathematical or physical. Since they are all solids, it is interesting to create a device that demonstrates the vibrations of liquid or gaseous bodies.
To do this, you can use the idea inherent in the design of a water clock. Two one and a half liter bottles are connected in the same way as in a water clock, by fastening the lids. The cavities of the bottles are connected by a glass tube 15 centimeters long, with an internal diameter of 4-5 millimeters. The side walls of the bottles should be smooth and non-rigid, easily crumpled when squeezed.
To start oscillations, a bottle of water is placed on top. Water from it immediately begins to flow through the tube into the lower bottle. After about a second, the stream spontaneously stops flowing and gives way to a passage in the tube for counter-propagation of a portion of air from the lower bottle to the upper one. The order in which counter flows of water and air pass through the connecting tube is determined by the difference in pressure in the upper and lower bottles and is adjusted automatically.
Pressure fluctuations in the system are evidenced by the behavior of the side walls of the upper bottle, which periodically compress and expand in time with the release of water and the intake of air. Since the process is self-regulating, this aerohydrodynamic system can be called self-oscillating.
THERMAL FOUNTAIN
This experiment demonstrates a stream of water flying out of a bottle under the influence of excess pressure in it. The main design detail of the fountain is the jet installed in the bottle cap. The jet is a screw, along the longitudinal axis of which there is a through hole of small diameter. Convenient in a pilot installation
use a jet from a used gas lighter.
A soft plastic tube is tightly placed at one end onto the nozzle, and its other open end is located near the bottom of the bottle. About a third of the bottle's volume is taken up by cool water. The cap on the bottle must be tightly screwed on.
To obtain a fountain, pour warm water over the bottle from a jug. The air enclosed in the bottle quickly warms up, its pressure rises, and the water is pushed out in the form of a fountain to a height of up to 80 centimeters.
This experiment can be used to demonstrate, firstly, the dependence of gas pressure on its temperature and, secondly, the work done by expanding air to raise water.
ATMOSPHERE PRESSURE
We all constantly remain at the bottom of the ocean of air under the pressure of the gravity of its many kilometers thick thickness. But we don’t notice this heaviness, just as we don’t think about the need to inhale and exhale this air from time to time.
To show the effect of atmospheric pressure, you need hot water, but not boiling water, so that the bottle does not deform. One hundred to two hundred grams of such water are poured into a bottle and shaken vigorously several times, thereby warming up the air in the bottle. Then the water is poured out, and the bottle is immediately tightly capped and placed on the table for viewing.
At the moment the bottle was sealed, the air pressure in it was the same as the external atmospheric pressure. Over time, the air in the bottle cools and the pressure inside it drops. The resulting pressure difference on both sides of the walls of the bottle leads to its squeezing, accompanied by a characteristic crunch.
What science is rich in interesting facts? Physics! 7th grade is the time when schoolchildren begin to study it. So that a serious subject does not seem so boring, we suggest starting your studies with interesting facts.
Why are there seven colors in the rainbow?
Interesting facts about physics can even involve rainbows! The number of colors in it was determined by Isaac Newton. Aristotle was also interested in such a phenomenon as the rainbow, and its essence was discovered by Persian scientists back in the 13-14th century. However, we are guided by the description of the rainbow that Newton made in his work "Optics" in 1704. He isolated the colors using a glass prism.
If you look closely at a rainbow, you can see how colors smoothly flow from one to another, forming a huge number of shades. And Newton initially identified only five main ones: violet, blue, green, yellow, red. But the scientist had a passion for numerology, and therefore wanted to bring the number of colors to the mystical number “seven”. He added two more colors to the description of the rainbow - orange and blue. This is how a seven-color rainbow turned out.
Liquid form
Physics is all around us. Interesting facts can surprise us, even when it comes to something as common as ordinary water. We are all used to thinking that a liquid does not have its own shape; even a school physics textbook says this! However, it is not. The natural shape of a liquid is a sphere.
Height of the Eiffel Tower
What is the exact height of the Eiffel Tower? And it depends on the weather! The fact is that the height of the tower varies by as much as 12 centimeters. This occurs because in hot sunny weather the structure heats up, and the temperature of the beams can reach up to 40 degrees Celsius. And as you know, substances can expand under the influence of high temperature.
Dedicated scientists
Interesting facts about physicists can not only be funny, but also tell about their dedication and devotion to their favorite work. While studying the electric arc, physicist Vasily Petrov removed the top layer of skin on his fingertips to sense weak currents.
And Isaac Newton inserted a probe into his own eye to understand the nature of vision. The scientist believed that we see because light presses on the retina.
Quicksand
Interesting facts about physics can help you understand the properties of such an interesting thing as quicksand. They represent: A person or animal cannot sink completely into quicksand due to its high viscosity, but it is also very difficult to get out of it. To pull your foot out of quicksand, you need to make an effort comparable to lifting a car.
You cannot drown in it, but dehydration, sun, and tides pose a danger to life. If you fall into quicksand, you need to lie on your back and wait for help.
Supersonic speed
You know what the first device was that overcame the Common Shepherd's Whip. The click that scares cows is nothing more than a pop when overcome. When hit hard, the tip of the whip moves so fast that it creates a shock wave in the air. The same thing happens with an airplane flying at supersonic speed.
Photon spheres
Interesting facts about physics and the nature of black holes are such that sometimes it is simply impossible to even imagine the implementation of theoretical calculations. As you know, light consists of photons. When photons fall under the influence of a black hole's gravity, they form arcs, regions where they begin to orbit. Scientists believe that if you place a person in such a photon sphere, he will be able to see his own back.
Scotch
It's unlikely that you've unwound tape in a vacuum, but scientists have done it in their laboratories. And they found out that when unwinding, a visible glow and X-ray emission occurs. The power of X-ray radiation is such that it even allows you to take pictures of body parts! But why this happens is a mystery. A similar effect can be observed when asymmetric bonds in a crystal are destroyed. But here's the problem - there is no crystalline structure in the tape. So scientists will have to come up with another explanation. There is no need to be afraid of unwinding the tape at home - no radiation occurs in the air.
Experiments on humans
In 1746, the French physicist and part-time priest Jean-Antoine Nollet investigated the nature of electric current. The scientist decided to find out what the speed of electric current is. Here's how to do it in a monastery...
The physicist invited 200 monks to the experiment, connected them using iron wires and discharged a battery of newly invented Leyden jars into the poor fellows (they are the first capacitors). All the monks reacted to the blow at the same time, and this made it clear that the speed of the current was extremely high.
Brilliant loser
Interesting facts from the lives of physicists can give false hope to unsuccessful students. There is a legend among careless students that the famous Einstein was a real bad student, knew little mathematics and generally failed his final exams. And nothing, it became worldwide. We hasten to disappoint: Albert Einstein began to show remarkable mathematical abilities as a child and had knowledge that far exceeded the school curriculum.
Perhaps rumors about the scientist’s poor performance arose because he did not immediately enter the Higher Polytechnic School of Zurich. Albert passed the exams in physics and mathematics brilliantly, but did not score the required number of points in other disciplines. Having improved his knowledge in the necessary subjects, the future scientist successfully passed the exams the following year. He was 17 years old.
Birds on a wire
Have you noticed that birds love to sit on wires? But why don’t they die from electric shock? The thing is that the body is not a very good conductor. The bird's feet create a parallel connection through which a small current flows. Electricity prefers wire, which is the best conductor. But as soon as the bird touches another element, for example, a grounded support, electricity rushes through its body, leading to death.
Hatches against cars
Interesting facts about physics can be remembered even while watching urban Formula 1 races. Sports cars move at such high speeds that a low pressure is created between the bottom of the car and the road surface, which is quite enough to lift the manhole cover into the air. This is exactly what happened at one of the city races. The manhole cover collided with the next car, causing a fire and the race was stopped. Since then, to avoid accidents, hatch covers have been welded to the rim.
Natural nuclear reactor
One of the most serious branches of science is nuclear physics. There are interesting facts here too. Did you know that 2 billion years ago there was a real natural nuclear reactor operating in the Oklo area? The reaction continued for 100,000 years until the uranium vein was exhausted.
An interesting fact is that the reactor was self-regulating - water entered the vein, which played the role of a neuron inhibitor. When the chain reaction was active, the water boiled away and the reaction weakened.
If you think physics is a boring and unnecessary subject, then you are deeply mistaken. Our entertaining physics will tell you why a bird sitting on a power line does not die from electric shock, and a person caught in quicksand cannot drown in it. You will find out whether there really are no two identical snowflakes in nature and whether Einstein was a poor student at school.
10 interesting facts from the world of physics
Now we will answer questions that concern many people.
Why does a train driver back up before moving off?
This is all due to the force of static friction, under the influence of which the train cars are standing motionless. If the locomotive simply moves forward, it may not move the train. Therefore, it slightly pushes them back, reducing the static friction force to zero, and then accelerates them, but in a different direction.
Are there identical snowflakes?
Most sources claim that there are no identical snowflakes in nature, since their formation is influenced by several factors: air humidity and temperature, as well as the flight path of the snow. However, interesting physics says: it is possible to create two snowflakes of the same configuration.
This was experimentally confirmed by researcher Karl Libbrecht. Having created absolutely identical conditions in the laboratory, he obtained two externally identical snow crystals. True, it should be noted: their crystal lattice was still different.
Where in the Solar System are the largest reserves of water?
You'll never guess! The largest reservoir of water resources in our system is the Sun. The water there is in the form of steam. Its highest concentration is found in places we call “sunspots.” Scientists even calculated: in these areas the temperature is one and a half thousand degrees lower than in other areas of our hot star.
What invention of Pythagoras was created to combat alcoholism?
According to legend, Pythagoras, in order to limit the consumption of wine, made a mug that could be filled with an intoxicating drink only to a certain level. As soon as you exceeded the norm by even a drop, the entire contents of the mug flowed out. This invention is based on the law of communicating vessels. The curved channel in the center of the mug does not allow it to be filled to the brim, “riding” the container of all contents when the liquid level is above the bend of the channel.
Is it possible to turn water from a conductor into a dielectric?
Interesting physics says: it’s possible. Current conductors are not the water molecules themselves, but the salts contained in it, or rather their ions. If they are removed, the liquid will lose its ability to conduct electricity and become an insulator. In other words, distilled water is a dielectric.
How to survive a falling elevator?
Many people think that you need to jump when the cabin hits the ground. However, this opinion is incorrect, since it is impossible to predict when the landing will occur. Therefore, entertaining physics gives another advice: lie with your back on the floor of the elevator, trying to maximize the area of contact with it. In this case, the force of the impact will not be directed to one area of the body, but will be evenly distributed over the entire surface - this will significantly increase your chances of survival.
Why doesn't a bird sitting on a high voltage wire die from electric shock?
Birds' bodies do not conduct electricity well. By touching the wire with its paws, the bird creates a parallel connection, but since it is not the best conductor, charged particles do not move through it, but along the cable conductors. But if the bird comes into contact with a grounded object, it will die.
The mountains are closer to the heat source than the plains, but at their peaks it is much colder. Why?
This phenomenon has a very simple explanation. The transparent atmosphere allows the sun's rays to pass through without hindrance, without absorbing their energy. But the soil absorbs heat well. It is from this that the air then warms up. Moreover, the higher its density, the better it retains the thermal energy received from the earth. But high in the mountains the atmosphere becomes rarefied, and therefore less heat is retained in it.
Can quicksand suck you in?
There are often scenes in films where people “drown” in quicksand. In real life, says entertaining physics, this is impossible. You won’t be able to get out of a sandy swamp on your own, because to pull out just one leg, you’ll have to put in as much effort as it takes to lift a medium-weight passenger car. But you won’t be able to drown either, since you’re dealing with a non-Newtonian fluid.
Rescuers advise in such cases not to make sudden movements, lie down with your back down, spread your arms to the sides and wait for help.
Does nothing exist in nature, watch the video:
Amazing incidents from the lives of famous physicists
Outstanding scientists are mostly fanatics of their field, capable of anything for the sake of science. For example, Isaac Newton, trying to explain the mechanism of perception of light by the human eye, was not afraid to experiment on himself. He inserted a thin ivory probe into the eye while pressing on the back of the eyeball. As a result, the scientist saw rainbow circles in front of him and thus proved: the world we see is nothing more than the result of light pressure on the retina.
Russian physicist Vasily Petrov, who lived in the early 19th century and studied electricity, cut off the top layer of skin on his fingers to increase their sensitivity. At that time, there were no ammeters and voltmeters that made it possible to measure the strength and power of current, and the scientist had to do it by touch.
The reporter asked A. Einstein whether he writes down his great thoughts, and if he writes them down, where - in a notebook, a notebook or a special card index. Einstein looked at the reporter’s voluminous notebook and said: “My dear! Real thoughts come to mind so rarely that it is not difficult to remember them.”
But the Frenchman Jean-Antoine Nollet preferred to experiment on others. Conducting an experiment in the mid-18th century to calculate the speed of transmission of electric current, he connected 200 monks with metal wires and passed voltage through them. All participants in the experiment twitched almost simultaneously, and Nolle concluded: the current runs through the wires very, very quickly.
Almost every schoolchild knows the story that the great Einstein was a poor student in his childhood. However, in fact, Albert studied very well, and his knowledge of mathematics was much deeper than what the school curriculum required.
When the young talent tried to enter the Higher Polytechnic School, he scored the highest score in the core subjects - mathematics and physics, but in other disciplines he had a slight deficiency. On this basis he was refused admission. The next year, Albert showed excellent results in all subjects, and at the age of 17 he became a student.
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WHAT AIR CAN DO
Experience 1
He can, for example, flip a coin! Place a small coin on the table and throw it into your hand with a push of air. To do this, holding your hand behind the coin, blow sharply onto the table. Just not in the place where the coin lies, but at a distance of 4-5 cm in front of it.
The air compressed by your breath will penetrate under the coin and throw it straight into your handful.
A few trials - and you will learn to take a coin from the table without touching it with your hand!
Experience 2
If you have a narrow conical glass, you can do another fun experiment with coins. Place a penny at the bottom of the glass and a nickel on top. It will lie horizontally, like a lid, although it does not reach the edge of the glass.
Now blow sharply on the edge of the penny.
It will stand on its edge, and the penny will be thrown out with compressed air. After this, the nickel will fall into place. So the invisible man helped you get a penny from the bottom of the glass without touching it or the penny lying on top.
Experience 3
A similar experiment can be done with egg cups. Place two of these glasses side by side and put an egg in the one closest to you.
In case of failure, take a hard-boiled egg. Now blow strongly and sharply into the place indicated by the arrow in the picture, right at the very edge of the glass.
The egg will jump up and “transplant” into the empty glass!
The invisible air slipped between the edge of the glass and the egg, burst into the glass, and so hard that the egg jumped up!
For some, this experience does not work out - “they lack the spirit.” But if instead of a hard-boiled egg you take an empty, blown-out shell, you will surely succeed!
HEAVY AIR
Take a wide wooden ruler (which you don't mind). Balance it on the edge of the table so that with the slightest pressure on the free end the ruler will fall. Now spread a newspaper on the table on top of the ruler. Gently spread it out, smooth it out with your hands, straighten out all the wrinkles.
Previously, the ruler could be tipped over with your finger. Now a newspaper has been added, but how much does it weigh? Come on, be bold: stand on the side of the ruler and hit its end with your fist!
Even my fist hurt, and the ruler lay there as if it was nailed down. Well, now we'll show her how to resist! Take a stick and hit with all your might. Bang! The ruler is in half, and the newspaper lies as if nothing had happened.
Why was the newspaper so heavy?
Yes, because air is pressing on it from above. 1 kg per square centimeter. And the newspaper has so many square centimeters! Well, calculate how much area this is? Approximately 60 x 42 = 2520 cm2. This means that the air presses on her with a force of two and a half thousand kilograms, two and a half tons!
Lift the newspaper slowly - the air will penetrate under it and press down from below with the same force. But try to tear her off the table at once, and you’ve already seen what happens. The air does not have time to get under the newspaper - and the ruler breaks in half!
SCHOOL RUBBER SUCKER
Of the three objects named in the title, the octopus is the least convenient for experiments. Firstly, it is difficult to get, and secondly, an octopus is not to be trifled with. How it grabs with its terrible tentacles, how it sucks with suction cups - you won’t be able to tear it off!
Zoologists say that the octopus's sucker is shaped like a cup with a circular muscle. The octopus tenses its muscles; the cup shrinks and becomes narrower. And then, when this cup presses against the prey, the muscle relaxes.
Look how interesting it is: in order to hold its prey, the octopus does not tense its muscles, but relaxes them! And still the suckers stick. Like a radish on a plate!
Experience
You and I had to abandon experiments with a living octopus. But we will still make one suction cup - an artificial suction cup, from a school gum.
Take a soft rubber band and make a hole in the middle of one side. This will be the suction cup. Well, let’s use your muscles. After all, they are only needed to squeeze the suction cup at first, and then they still relax, so that the hand can be removed.
Squeeze the rubber band to make the cup smaller and press it onto the plate. Just wet it first: the gum is not a radish, it doesn’t have its own juice. By the way, the octopus also “works” with wet suction cups.
Did you press the rubber band?
Now let go, she has attached herself securely.
There are also soap dishes with rubber suction cups. They stick to the tiled bathroom wall. They also need to be wetted first, and then pressed against the wall and released. Hold on!
Well, now about the fly!
Tell me, have you ever wondered how she walks on the wall and even on the ceiling?
There is even a riddle: “What’s upside down above us?” Maybe the fly has claws at the ends of its legs? The hooks with which it clings to uneven walls and ceilings? But she walks completely freely on the window glass and on the mirror. There's nothing there for a fly to grab onto. It turns out that flies also have suction cups on their legs.
So, after this, assert that there is nothing in common between a fly and an octopus.
HOW TO EMPTY THE GLASS?
The glass and bottle are filled with water. You need to empty the glass with the bottle without emptying it.
Make two holes in the bottle cap and push two straws through them, one equal in length to the height of the glass, the other twice as long. Then seal one end of the smaller straw with bread crumb and plug the bottle with a stopper so that the open ends of the straws fit into the bottle.
Now if you turn the bottle upside down, water will start flowing out of the large straw. Tip the bottle over a glass of water so that the small straw touches the bottom of the glass, and use scissors to cut off the end covered with bread crumb. Water will flow out of the large straw until the glass is empty. Why?
This is explained as follows: the straws act as a siphon. The void in the bottle formed by the flowing water is immediately filled with water from the glass, which is driven into the bottle by the air pressure on the surface of the water in the glass.
