Entertaining physics pressure. Interesting experiments with atmospheric pressure

And again I will allow myself to touch upon the 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 wrote a whole galaxy of popular science books, among which "Entertaining Physics" is only the most famous. It has withstood more than 20 reprints (I cannot say for sure, but if recently it has been reprinted again, then it will already be about 30 reprints). This two-volume edition was wildly popular in the then Soviet Union and now it would be called a bestseller.

For a long time I wanted to buy it myself and it was purchased (it was several years ago, and I have been looking for this two-volume edition 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 for the eyes. Moreover, with the help of this book, you can put on a number of very instructive and serious experiments at home.

Plus, in addition to everything else, it also discusses in detail the most typical mistakes science fiction writers specializing in science fiction (especially loved by the author Herbert Wells and Jules Verne), however, Yakov Isidorovich does not bypass 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 his book Wanderings Abroad, the American comedian Mark Twain tells about one case of his Alpine trip - a case, of course, a fictional one:

Our troubles are over; so people could rest, 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 the barometer, but, unfortunately, I did not get any results. From my scientific readings, I knew that either a thermometer or a barometer should be boiled to obtain readings. Which one of the two - I probably did not know and therefore decided to boil both.

And yet he did not get any results. After examining both instruments, I saw that they were completely ruined: the barometer had only one copper needle, and a lump of mercury dangled in the bulb of the thermometer ...

I found another barometer; it was brand new and very good. For half an hour I boiled it in a pot with bean stew, which the cook cooked. The result was unexpected: the instrument stopped working, but the soup acquired such a strong barometer flavor that the head chef - a very intelligent person - changed its name in the list of dishes. The new dish got everyone's approval, so I ordered soup to be made every day from the barometer. Of course, the barometer was completely ruined, but I didn’t regret it too much. Since he did not help me determine the height of the terrain, then I no longer need him.

Joking 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 saw that the lower the pressure on water, the lower its boiling point. Since atmospheric pressure decreases with the rise in the mountains, the boiling point of water should also decrease. Indeed, the following boiling points of pure water are observed at various atmospheric pressures:

In Bern (Switzerland), where the average atmospheric pressure is 713 mm Hg. Art., water in open vessels boils already 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. As the water rises for every kilometer, the boiling point of water drops by 3 ° C. This means that if we measure the temperature at which water boils (according to Twain's expression, if "we will boil the thermometer"), then, referring to the corresponding table, we can find out the height of the place. To do this, of course, you must have at your disposal pre-compiled tables, which Mark Twain "simply" forgot.

The devices used for this purpose - hypsothermometers - are no less convenient to carry than metal barometers and give much more accurate readings.

Of course, the 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 lower the pressure. But even here either tables showing how the air pressure decreases as it rises above sea level is needed, or knowledge of the corresponding formula. All this seemed to be confused in the humorist's head and prompted him to "cook soup from a barometer."

I wonder how many readers of my blog knew the answer before the end of the passage? And who of them remembers (knows) this mysterious formula mentioned in an excerpt from the book?

Yes, by the way, thanks to atmospheric pressure, you can show very interesting physics tricks. When I was a physics teacher at school, I showed schoolchildren a simple trick while studying the topic "atmospheric pressure". I took a glass tube with two open ends about 50 cm long. With a flattened (narrower) end, I put the tube into a vessel with water and waited for water to be drawn into 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 gushed at a fairly decent height. Then, imperceptibly replacing the vessel with water, I gave the students the opportunity to repeat the trick and they did not succeed. The inevitable "debriefing" began on which the essence of this trick was revealed.

Some of you have already guessed what was the catch?

P.S. A hypo thermometer is also known as a thermobarometer. Note that at a pressure close to 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 about 30 m). The scale of a modern thermobarometer is divided into hundredths of a degree or the corresponding units of pressure in mm Hg. 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.

WHAT CAN AIR

Test 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 with a shield, blow sharply on the table. Only 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 toss it straight into your handful.

A few tests - and you will learn how to take a coin from the table without touching it with your hand!

Test 2

If you have a narrow conical glass, you can make another fun coin experience. Put a penny on the bottom of the glass, and a penny 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 nickel.

It will stand on its edge, and a penny will be thrown out with compressed air. After that, the penny will fall into place. So the invisible person helped you to get a penny from the bottom of the glass, without touching either it or the penny lying on top.

Test 3

A similar experience can be done with egg cups. Put two such glasses side by side and in the one that is closer to you, put the egg.

In case of failure, take a tough egg. And now blow strongly and sharply into the place indicated by the arrow in the figure, just at the very edge of the glass.

The egg will jump and "change" into an empty glass!
The invisible air slipped between the edge of the glass and the egg, burst into the glass, so much so that the egg jumped up!

For some, this experience does not work out - "lacks the spirit." But if, instead of a tough egg, you take an empty, blown shell, it will work out for sure!

HEAVY AIR

Take a wide wooden ruler (which is not a pity). Balance it at the edge of the table so that the ruler falls down with the slightest pressure on the free end. Now spread the newspaper on the table on top of the ruler. Spread it out neatly, smooth it out with your hands, smooth out all the folds.

Previously, the ruler could be knocked over with your finger. Now the newspaper has been added, but does it weigh a lot? Come on, bolder: stand on the side of the ruler and hit the end with your fist!

Even the fist is sick, and the ruler lies as if nailed in by nails. Well, now we'll show her how to resist! Take a stick and hit it with full swing. Bang! The ruler is in half, and the newspaper lies to itself as if nothing had happened.

Why was the newspaper so heavy?
Because the air presses on her from above. 1 kg for each square centimeter... And oh, how many square centimeters the newspaper has! Well, count, what area is it? 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!

Raise the newspaper slowly - the air will penetrate under it and press from below with the same exact 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 items named in the title, the octopus is the least suitable for experiments. Firstly, it is difficult to get it, and secondly, jokes with the octopus are bad. How it grabs with its terrible tentacles, how it sucks with suckers - you can't tear it off!

Zoologists say that the octopus has a cup-shaped sucker with a ring muscle. The octopus strains the muscle - the cup contracts, becomes narrower. And then, when this cup is pressed against the prey, the muscle relaxes.

Look how interesting: in order to hold on to its prey, the octopus does not strain its muscles, but relaxes them! And all the same, the suckers stick. Like a radish on a plate!

An experience

You and I had to give up experiments with a live octopus. But we will still make one suction cup - an artificial suction cup, from a school rubber band.

Take a soft elastic band and hollow out a groove in the middle of one side. This will be the suction cup. Well, we use your muscles. After all, they are only needed to squeeze the suction cup first, and then they still relax, so that the hand can be removed.
Squeeze the elastic to make the cup smaller and press it against the plate. Just wet it first: the gum is not a radish, it has no juice of its own. By the way, the octopus also "works" with wet suckers.

Did you press the rubber band?
Now let go, it sucked securely.
There are also soap dishes with rubber suction cups. They stick to the tiled bathroom wall. They, too, must first be moistened, and then pressed against the wall and released. Hold on!

Well, now about the fly!
Tell me, have you ever thought about how she walks on the wall and even on the ceiling?

There is even such a riddle: "What's upside down above us?" Maybe a fly has a claw at the ends of its legs? Hooks with which it clings to the unevenness of the walls and ceiling? But after all, she walks on the window glass completely freely, and on the mirror. There, too, and the fly has nothing to catch. It turns out that the fly also has suckers on its legs.

So affirm after that that there is nothing in common between a fly and an octopus.

HOW TO EMPTY A GLASS?

The glass and bottle are filled with water. It is necessary to empty the glass with a bottle without emptying it.
Poke two holes in the bottle cork and poke two straws through them, one equal in length to the height of the glass, the other twice as long. Then cover one end of the smaller straw with bread crumb and plug the bottle so that the open ends of the straws enter the bottle.

Now, if you turn the bottle over, 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 cut the end sealed with bread crumb with scissors. Water flows 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 out 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.

If you think physics is a boring and unnecessary subject, you are deeply mistaken. Our entertaining physics will tell you why a bird sitting on a power line does not die from an electric shock, and a person caught in quicksand cannot drown in them. You will find out if there really are no two in nature identical snowflakes and whether Einstein was a poor student at school.

10 fun facts from the world of physics

Now we will answer the questions that concern many people.

Why does the train driver backtrack before moving off?

It is all the fault of the static friction force, under the influence of which the train carriages are standing motionless. If the locomotive just goes forward, it may not budge the train. Therefore, he slightly pushes them back, reducing to zero the force of friction at rest, and then gives them acceleration, but in a different direction.

Are there the same snowflakes?

Most sources claim: there are no identical snowflakes in nature, since several factors affect their formation at once: humidity and air temperature, as well as the trajectory of the snow. However, entertaining physics says: you can create two snowflakes of the same configuration.

This was experimentally confirmed by researcher Karl Libbrecht. Having created absolutely identical conditions in the laboratory, he received two externally completely identical snow crystals. True, it should be noted: crystal cell they all the same was different.

Where are the largest reserves of water in the solar system?

You will never guess! The most voluminous storage of water resources in our system is the Sun. The water is there in the form of steam. Its greatest concentration is found in places that we call "sunspots." Scientists even calculated that in these areas the temperature is one and a half thousand degrees lower than in other parts of our hot star.

What invention of Pythagoras was created to combat alcoholism?

According to legend, Pythagoras, in order to limit the use of wine, made a mug that could be filled with a hoppy drink only up to a certain mark. It was worth exceeding the norm by even a drop, and 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 circle prevents it from filling to the brim, “ridding” the container of all its contents when the liquid level is above the bend of the channel.

Is it possible to turn water from a conductor into a dielectric?

Entertaining physics says: you can. The current conductors are not the water molecules themselves, but the salts contained in it, or rather their ions. If 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 in a falling elevator?

Many people think: you need to jump at the moment the cockpit 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 blow will not be directed to one part 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 an electric shock?

Feathered bodies do not conduct electric current well. By touching the paws to the wire, the bird creates a parallel connection, but since it is not the best conductor, the charged particles do not move through it, but along the cable veins. But as soon as the bird touches a grounded object, it will die.

The mountains are closer to the heat source than the plains, but on their tops it is much colder. Why?

This phenomenon has a very simple explanation. The transparent atmosphere freely lets the sun's rays through without absorbing their energy. But the soil perfectly absorbs heat. It is from her that the air is then warmed up. Moreover, the higher its density, the better it retains what it receives from the ground. thermal energy... But high in the mountains, the atmosphere becomes thinner, and therefore less heat is "retained" in it.

Can Quicksand Suck?

In films, there are often scenes where people "drown" in quicksand. IN real life- says entertaining physics - this is impossible. You will not be able to get out of the sandy swamp on your own, because in order to pull out only one leg, you will have to make as much effort as it takes to lift a medium-weight car. But you also cannot drown, since you are dealing with a non-Newtonian liquid.

Rescuers advise in such cases not to make sudden movements, lie with your back down, spread your arms to the sides and wait for help.

Does nothing exist in nature, see the video:

Amazing incidents from the life of famous physicists

Outstanding scientists for the most part are fanatics of their field, capable of anything for the sake of science. So, for example, Isaac Newton, trying to explain the mechanism of perception of light by the human eye, was not afraid to put the experiment on himself. He inserted a thin, ivory-shaped probe into the eye, simultaneously pressing on the back of the eyeball. As a result, the scientist saw rainbow circles in front of him and thus proved that the world we see is nothing more than the result of the pressure of light on the retina.

Russian physicist Vasily Petrov, who lived in early XIX century and was engaged in the study of electricity, cut off the top layer of skin on his fingers to increase their sensitivity. At that time, ammeters and voltmeters did not yet exist, which made it possible to measure the strength and power of the current, and the scientist had to do it by touch.

The reporter asked A. Einstein if he writes down his great thoughts, and if he does, then where - in a notebook, notebook or special file cabinet. Einstein looked at the reporter's bulky 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 put the experiment on others, Conducting an experiment to calculate the transmission rate in the middle of the 18th century 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 well, oh-oh-very quickly.

Almost every student knows the story that the great Einstein was a poor student in childhood. However, in fact, Albert studied very well, and his knowledge of mathematics was much deeper than the school curriculum required.

When the young talent tried to enter the higher polytechnic school, he scored highest mark on profile subjects- mathematics and physics, but in other disciplines he had a small shortfall. On this basis, he was denied admission. The following year, Albert showed excellent results in all subjects, and at the age of 17 he became a student.

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What science is rich in Interesting Facts? Physics! Grade 7 is the time when students 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 a rainbow?

Fun facts about physics can even touch the rainbow! The number of colors in it was determined by Isaac Newton. Aristotle was interested in such a phenomenon as the rainbow, and the Persian scientists discovered its essence back in the 13-14 century. Nevertheless, we are guided by Newton's description of the rainbow in his work "Optics" in 1704. He highlighted the colors with a glass prism.

If you look closely at the 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: purple, 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-colored rainbow turned out.

Liquid shape

Physics is around us. Interesting facts may surprise us, even when it comes to such a familiar thing as plain water... We are all used to thinking that a liquid does not have its own form, even says this school textbook in physics! However, it is not. Natural shape liquids - a ball.

Eiffel Tower Height

What is the exact height Eiffel tower? It depends on the weather! The fact is that the height of the tower fluctuates by as much as 12 centimeters. It comes from being hot sunny weather the structure heats up and the temperature of the beams can go up to 40 degrees Celsius. And as you know, substances can expand under the influence of high temperatures.

Selfless Scientists

Interesting facts about physicists can be not only funny, but also tell about their dedication and dedication to their favorite work. While studying the electric arc, physicist Vasily Petrov removed the top layer of skin at his fingertips in order 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 an animal cannot completely immerse themselves in quicksand due to the high viscosity, but it is also very difficult to get out of it. Pulling a leg out of the quicksand requires an effort comparable to lifting a car.

You cannot drown in it, but dehydration, sun, tides pose a danger to life. If you get into quicksand, you need to lie on your back and wait for help.

Supersonic speed

You know what the first adaptation was to overcome the Ordinary Shepherd's Whip. The click that scares the cows is nothing more than a clap when overcoming. With a strong impact, the tip of the whip moves so fast that it creates a shockwave in the air. The same thing happens with an airplane flying at supersonic speed.

Photonic spheres

Interesting facts about the physics and nature of black holes are such that sometimes it is simply impossible to even imagine the implementation of theoretical calculations. As you know, light is composed of photons. When photons fall under the influence of gravity of a black hole, they form arcs, areas where they begin to rotate in an orbit. Scientists believe that if you place a person in such a photonic sphere, then he will be able to see his own back.

Scotch

It is unlikely that you unwound the tape in a vacuum, but scientists in their laboratories did it. And they found out that when unwinding, there is a visible glow and X-ray radiation. Power x-ray 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 are broken in a crystal. But here's the bad luck - there is no crystal structure in the scotch tape. So scientists will have to come up with another explanation. Do not be afraid to unwind the tape at home - no radiation occurs in the air.

Experiments on humans

In 1746, French physicist and, concurrently, priest Jean-Antoine Nollet investigated the nature of electric current. The scientist decided to find out what the speed of the electric current is. Here's just how to do it in a monastery ...

The physicist invited 200 monks to the experiment, connected them with iron wires and discharged a battery from the recently invented Leyden jars (they are the first capacitors) into the poor fellows. All the monks reacted to the blow at the same time, and this made it clear that the speed of the current is extremely high.

Genius poor student

Interesting facts from the life of physicists can give false hopes to unsuccessful students. There is a legend among the careless students that famous Einstein was a real poor student, did not know mathematics well and generally flunked final exams... And nothing, he became worldwide. We hasten to disappoint: Albert Einstein began to show remarkable mathematical ability even in childhood and had knowledge that far exceeded the school curriculum.

Perhaps the rumors about the poor academic performance of the scientist arose because he did not immediately enter the Higher Polytechnic School of Zurich. Albert brilliantly passed the exams in physics and mathematics, but in other disciplines he did not score the required number of points. Pulling up knowledge on 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 point is that the body is not a very good vehicle. The paws of the bird 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 fireballs

Interesting facts about physics can be remembered even while watching Formula 1 city races. Sports cars move with such high speed that a low pressure is created between the bottom of the car and the surface of the road, which is quite enough to lift the hatch cover into the air. This is exactly what happened at one of the city races. The sunroof collided with the next car, a fire broke out, and the race was stopped. Since then, to avoid accidents, the sunroof 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 as well. Did you know that a real natural nuclear reactor operated in the Oklo area 2 billion years ago? The reaction lasted 100,000 years until the uranium vein was depleted.

An interesting fact is that the reactor was self-regulating - water entered the vein, which played the role of a neuron moderator. With an active course chain reaction the water boiled away and the reaction weakened.