Entertaining physics pressure. Interesting experiments with atmospheric pressure. natural nuclear reactor
What science is rich in interesting facts? Physics! Grade 7 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 entertaining facts.
Why are there seven colors in the rainbow?
Interesting facts about physics can even touch the rainbow! The number of colors in it was determined by Isaac Newton. Even Aristotle was interested in such a phenomenon as a rainbow, and its essence was discovered by Persian scientists in the 13-14th century. However, we are guided by the description of the rainbow that Newton made in his Optics in 1704. He singled out the colors with a glass prism.
If you look closely at the rainbow, you can see how the colors smoothly flow from one to another, forming a huge number of shades. And Newton initially singled out only five main ones: purple, blue, green, yellow, red. But the scientist had a passion for numerology, and therefore he 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. So it turned out a seven-color rainbow.
Liquid form
Physics is around us. Interesting facts may surprise us, even when it comes to such a familiar thing as ordinary water. We are all used to thinking that a liquid does not have its own shape, even a school textbook on physics says this! However, it is not. The natural shape of a liquid is a sphere.
Eiffel tower height
What is the exact height of the Eiffel Tower? And it depends on the weather! The fact is that the height of the tower fluctuates by as much as 12 centimeters. This is due to the fact that in hot sunny weather the building 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.
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 an electric arc, physicist Vasily Petrov removed the top layer of skin on his fingertips to feel weak currents.
And Isaac Newton introduced 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 to understand the properties of such an entertaining thing as quicksand. They represent a Human or animal cannot completely sink into quicksand due to its high viscosity, but it is also very difficult to get out of it. To get your foot out of the quicksand, you need to make an effort comparable to lifting a car.
You can’t drown in it, but life is dangerous from dehydration, the sun, and hot flashes. If you get into quicksand, you need to lie on your back and wait for help.
supersonic speed
You know what was the first device that overcame the Common Shepherd's Whip. The click that frightens the cows is nothing more than a pop when overcoming. With a strong blow, the tip of the whip moves so fast that it creates a shock wave in the air. The same thing happens with an aircraft flying at supersonic speeds.
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 made up of photons. Falling under the influence of the gravity of a black hole, photons form arcs, areas where they begin to orbit. Scientists believe that if you put a person in such a photon sphere, he will be able to see his own back.
Scotch
It is unlikely that you unwound tape in a vacuum, but scientists in their laboratories did it. And they found that when unwinding, a visible glow and X-rays appear. The power of X-ray radiation is such that it even allows you to take pictures of parts of the body! Why this happens is a mystery. A similar effect can be observed upon the destruction of asymmetric bonds in a crystal. But here's the problem - there is no crystalline structure in 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, the French physicist and part-time priest Jean-Antoine Nollet investigated the nature of the electric current. The scientist decided to find out what is the speed of the electric current. 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 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.
Genius Loser
Interesting facts from the life of physicists can give false hopes to underachieving students. There is a legend among negligent students that the famous Einstein was a real loser, did not know mathematics well and generally flunked his final exams. And nothing, became world 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 the rumors about the poor performance of the scientist arose because he did not immediately enter the Zurich Polytechnic School. Albert brilliantly passed the exams in physics and mathematics, but in other disciplines he did not score the required number of points. 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 paws 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 at such high speeds that a low pressure is created between the bottom of the car and the road surface, which is enough to lift the hatch cover into the air. This is exactly what happened at one of the city races. The manhole cover collided with the next car, a fire broke out and the race was stopped. Since then, manhole covers have been welded to the rim to avoid accidents.
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 2 billion years ago, a real natural nuclear reactor operated in the Oklo region? The reaction proceeded for 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 the active course of the chain reaction, the water boiled away, and the reaction weakened.
Hello dear readers.
In the project "Playing Physics" there is a season of games and acquaintance with the concept. The first review of experiences from the Internet was devoted to. And today let's see what experiments are being done with water pressure, how they are playing with it.
The first thing I found was an article about pressure on the Cool Physics website. Many interesting problems - questions about the pressure of the liquid. And the experience in the figure is very revealing and interesting, as it seems to me. It is immediately clear and clearly shown that at different depths, the fluid pressure is different. 
At school (or at the institute?), we deduced Bernoulli's law for a long time using formulas. As a result, no one remembered the meaning. Me too. And it turns out everything, in principle, is simple. But it's paradoxical. And this is especially interesting for both adults and children). In the photo, an experiment with air according to this law, and it is possible with water.
I got an interesting game. It is, but of course it is not for toddlers. But it should be very interesting for schoolchildren to play like this.
And here is a video demonstrating the physical law. Almost a cartoon
You can experiment with Pascal's ball. Basically, it's just a regular spray gun. And what kind of scientific device turns out to be) We at school just squealed when demonstrating this experience. Although it seems that this was already the ninth grade) 
The experiment with communicating vessels is very interesting. It always seemed to me that the topic is very simple and boring. An, no. There are quite a few interesting and important moments in it. 
We place a metal bucket on a rotating circle. We drop a small container into it. Then pour liquid for ignition or alcohol into the container. We set fire to the liquid for ignition and begin to rotate the circle. Watching a real tornado.
When the circle unwinds, the flame begins to rise up and twists like a tornado. This happens because when the bucket rotates, it drags the air 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 from all over. districts. And he also inflates this fire, and since there is an ascending stream, a flame is formed inside, and due to the fact that the stream twists, the air also twists.
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. Outside, the air is cooler. And while the air in the bottle and outside is different, hot air tends to leave the bottle as quickly as possible. Due to these actions, a pressure drop occurs, which subsequently causes the testicle to fall to the bottom of the bottle.
3. According to the size of the plywood plank 10x10 cm, cut out a rubber pad from an old volleyball tube and attach it with buttons to the plywood. Pour some water into a half-liter glass jar, and a little alcohol on the water. Ignite the alcohol. After letting it burn for a short time, close the jar with a plank. The fire will go out. After 1-2 seconds, lift the plank. Together with it, a can rises, into which the rubber is drawn. How to explain the lifting of the can with the plank and the retraction of the rubber? Where is this phenomenon used in practice? During combustion, the air heats up. After closing the jar, the combustion process stops. The air starts to cool. A vacuum occurs in the can, due to which it is pressed against the plywood by atmospheric pressure. Rubber retraction is also explained by atmospheric pressure. Treatment with medical cups is based on this phenomenon.
4. EXPERIENCE WITH GLASSES (Magdeburg hemispheres).
Cut out a rubber or paper ring, taking into account the diameter of the faceted glass, and place it on the glass. Light a piece of paper or a small candle on fire, lower it into a glass and close it almost immediately with a second glass. Through. Raise the top glass for 1-2 seconds, followed by the bottom one.
5. Atomizer
Objective: To learn how a spray gun works. You will need a glass, scissors, two flexible straws. 
Pour into a glass of water.
Cut one straw near the corrugated part and place it vertically in a glass so that it comes out 1 cm corrugated from the water.
Position the second straw so that its edge touches the top edge of the straw standing in the water. Use to stop the folds of the corrugation on the vertical straw.
Blow strongly through the horizontal straw.
Water rises along a straw standing in the water and 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 pressure of the air 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 gun, the same thing happens. The air from the pear passes through the tube, the pressure in it drops, and because of this air rarefaction, the cologne rises 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 get a coin without getting their fingers wet. To conduct the experiment, you need another glass and several matches stuck in a cork floating on the water. Light the matches and quickly cover the floating burning boat with a glass without taking any coins. When the matches go out, the glass will fill with white smoke, and then all the water from the plate will automatically 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 a glass and keeps it there at a certain height is atmospheric pressure. Burning matches heated the air in the glass, its pressure increased, part of the gas came out. When the matches went out, the air cooled again, but when 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.
Experience 1. Take a plunger, which is used in plumbing, moisten its edges with water and press it against 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 part 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 together.
Experience 2. Press the plunger against the blackboard, hang a load of 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 inverted in the 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 from the bottle will spill out.
12. How we drink. Take two straws, one whole, make a small hole in the second. Through the first, water enters the mouth, through the second it does not. 13. If you pump out air from a funnel, the wide opening of which is covered with a rubber film, then the film is drawn inward, and then even bursts.Inside the funnel, the pressure decreases, under the influence of atmospheric pressure, the film is drawn inward. This is how the following phenomena can be explained: If you put a maple leaf to your lips and quickly draw in air, the leaf will burst with a crack. 
Equipment: rail 50-70 cm long, newspaper, meter.
Conduct: Put a rail on the table, a fully unfolded newspaper on it. If you slowly put pressure on the hanging end of the ruler, then it falls, and the opposite one rises along with the newspaper. If you sharply hit the end of the rail with a meter or hammer, then it breaks, and the opposite end with the newspaper does not even rise. How to explain it?
Explanation: Atmospheric air exerts pressure on the newspaper from above. By slowly pressing the end of the ruler, air penetrates under the newspaper and partially balances the pressure on it. With a sharp blow, due to inertia, 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 must be laid so that its end of 10 cm hangs. The newspaper should fit snugly against the rail and the table.
15. Entertaining experiments with atmospheric phenomena
AUTO OSCILLATIONS
Mechanical oscillatory motion is usually studied by considering the behavior of some kind of pendulum: spring, mathematical or physical. Since they are all solid bodies, it is interesting to create a device that demonstrates the vibrations of liquid or gaseous bodies.
To do this, you can use the idea embedded in the design of the water clock. Two one and a half liter bottles are connected in the same way as in a water clock, fastening the lids. The cavities of the bottles are connected with 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 crushed 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 jet spontaneously stops flowing and gives way to a passage in the tube for the oncoming movement of a portion of air from the lower bottle to the upper one. The order of passage of oncoming flows of water and air through the connecting tube is determined by the pressure difference in the upper and lower bottles and is automatically adjusted.
Pressure fluctuations in the system are evidenced by the behavior of the side walls of the upper bottle, which, in time with the release of water and the inlet of air, periodically squeeze and expand. Since the process is self-regulating, this aerohydrodynamic system can be called self-oscillatory.
THERMAL FOUNTAIN
In this experiment, a water jet is shown flying out of a bottle under the action of excess pressure in it. The main part of the fountain design 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. In a pilot plant it is convenient
use a jet from an exhausted gas lighter.
A soft plastic tube is tightly put on the jet at one end, and its other open end is located near the bottom of the bottle. About a third of the volume of the bottle is cool water. The cap on the bottle must be hermetically sealed.
To get a fountain, a bottle is poured over from a jug with warm water. The air enclosed in the bottle warms up quickly, its pressure rises, and the water is pushed out in the form of a fountain to a height of up to 80 centimeters.
This experience 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 stay at the bottom of the ocean of air under the pressure of the gravity of its multi-kilometer thickness. But we do not notice this heaviness, just as we do not think about the need to inhale and exhale this air from time to time.
To show the action of atmospheric pressure, hot water is needed, but not boiling water so that the bottle does not deform. One hundred to two hundred grams of such water is 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 closed with a lid and placed on the table for viewing.
At the time of corking the bottle, the air pressure in it was the same as the outside 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 bottle walls leads to its squeezing, accompanied by a characteristic crunch
And again, I 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 wrote a whole galaxy of popular science books, among which "Entertaining Physics" is just the most famous. It has withstood more than 20 reprints (I can't say for sure, but if it has been reprinted recently, it will be about 30 reprints). This two-volume book 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 for myself, and it was purchased (this was several years ago, and I have been 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 of knowledge of a school physics course for grades 7-9, it is enough for the eyes. Even more than that, with the help of this book, you can make a number of very instructive and serious experiments at home.
In addition to everything else, it also examines in detail the most typical mistakes of science fiction writers specializing in science fiction (HG Wells and Jules Verne are especially loved by the author), 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 quote one of the paragraphs of this wonderful two-volume book?
"Barometer Soup"
In his book Travels Abroad, the American humorist Mark Twain recounts one incident of his Alpine journey - an incident, of course, fictional:
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 height of the place where we were by means of a barometer, but, unfortunately, I did not get any results. I knew from my scientific readings that either the thermometer or the barometer had to be boiled to take a reading. Which of the two - I probably did not know and therefore decided to boil both.
Still got no results. Having examined both instruments, I saw that they were completely damaged: the barometer had only one copper needle, and a lump of mercury dangled in the thermometer ball ...
I found another barometer; it was brand new and very good. I boiled it for half an hour in a pot of bean soup that the cook was making. The result was unexpected: the instrument ceased to function, but the soup acquired such a strong taste of a barometer that the chief cook, a very intelligent man, changed its name in the list of dishes. The new dish won general approval, so I ordered barometer soup to be prepared every day. Of course, the barometer was completely flawed, but I didn't particularly regret it. If he did not help me determine the height of the terrain, then I no longer need him.
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 made a reservation 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, the boiling point of water must also decrease. Indeed, the following boiling points of pure water are observed at various atmospheric pressures:
| Boiling point, °C | Pressure, mm Hg 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 pressure of the atmosphere 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. For every kilometer you rise, the boiling point of water drops by 3°C. This means that if we measure the temperature at which water boils (in Twain's words, if "we boil a thermometer"), then consulting the corresponding table, we can find out the height of the place. To do this, of course, it is necessary to have at your disposal pre-compiled tables, 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 height 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 are needed showing how air pressure decreases as it rises above sea level, or knowledge of the corresponding formula. All this seems to have mixed up 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 excerpt? And which of them remembers (knows) this mysterious formula mentioned in the excerpt from the book?
Yes, by the way, thanks to atmospheric pressure, you can show very interesting physical tricks. When I was a physics teacher at school, I showed schoolchildren while studying the topic "atmospheric pressure" a simple trick. He took a glass tube with two open ends about 50 cm long. With a flattened (narrower) end, he placed the tube in a vessel with water and waited for water to fill up in the tube. Then he plugged the wider end 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 to a fairly decent height. Then, quietly replacing the vessel with water, I gave the opportunity to repeat the trick to the schoolchildren and they did not 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 hypsothermometer is also known as a thermobarometer. Note that at a 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 the equivalent elevation change of about 30m). The scale of a modern thermobarometer is divided into hundredths of a degree or the corresponding units of pressure in mmHg. Art. The composition of 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.