Buoyancy force of Archimedes cartoon. Academy of Entertaining Sciences

It would seem that there is nothing simpler than Archimedes' law. But once upon a time Archimedes himself really puzzled over his discovery. How it was?

There is an interesting story connected with the discovery of the fundamental law of hydrostatics.

Interesting facts and legends from the life and death of Archimedes

In addition to such a gigantic breakthrough as the discovery of Archimedes’ law itself, the scientist has a whole list of merits and achievements. In general, he was a genius who worked in the fields of mechanics, astronomy, and mathematics. He wrote such works as a treatise “on floating bodies”, “on the ball and cylinder”, “on spirals”, “on conoids and spheroids” and even “on grains of sand”. The latest work attempted to measure the number of grains of sand needed to fill the Universe.

Role of Archimedes in the Siege of Syracuse

In 212 BC, Syracuse was besieged by the Romans. 75-year-old Archimedes designed powerful catapults and light short-range throwing machines, as well as the so-called “Archimedes claws”. With their help, it was possible to literally turn over enemy ships. Faced with such powerful and technological resistance, the Romans were unable to take the city by storm and were forced to begin a siege. According to another legend, Archimedes, using mirrors, managed to set fire to the Roman fleet, focusing the sun's rays on the ships. The veracity of this legend seems doubtful, because None of the historians of that time mentioned this.

Death of Archimedes

According to many testimonies, Archimedes was killed by the Romans when they finally took Syracuse. Here is one of the possible versions of the death of the great engineer.

On the porch of his house, the scientist was thinking about the diagrams that he drew with his hand right in the sand. A passing soldier stepped on the drawing, and Archimedes, deep in thought, shouted: “Get away from my drawings.” In response to this, a soldier hurrying somewhere simply pierced the old man with a sword.

Well, now about the sore point: about the law and power of Archimedes...

How Archimedes' law was discovered and the origin of the famous "Eureka!"

Antiquity. Third century BC. Sicily, where there is still no mafia, but there are ancient Greeks.

An inventor, engineer and theoretical scientist from Syracuse (a Greek colony in Sicily), Archimedes served under King Hiero II. One day, jewelers made a golden crown for the king. The king, being a suspicious person, summoned the scientist to his place and instructed him to find out whether the crown contained silver impurities. Here it must be said that at that distant time no one had resolved such issues and the case was unprecedented.

Archimedes thought for a long time, came up with nothing, and one day decided to go to the bathhouse. There, sitting down in a basin of water, the scientist found a solution to the problem. Archimedes drew attention to a completely obvious thing: a body, immersed in water, displaces a volume of water equal to the body’s own volume.

It was then that, without even bothering to get dressed, Archimedes jumped out of the bathhouse and shouted his famous “Eureka,” which means “found.” Appearing to the king, Archimedes asked to give him ingots of silver and gold, equal in weight to the crown. By measuring and comparing the volume of water displaced by the crown and the ingots, Archimedes discovered that the crown was not made of pure gold, but was mixed with silver. This is the story of the discovery of Archimedes' law.

The essence of Archimedes' law

If you are asking yourself how to understand Archimedes' principle, we will answer. Just sit down, think, and understanding will come. Actually, this law says:

A body immersed in a gas or liquid is subject to a buoyancy force equal to the weight of the liquid (gas) in the volume of the immersed part of the body. This force is called the Archimedes force.

As we can see, the Archimedes force acts not only on bodies immersed in water, but also on bodies in the atmosphere. The force that makes a balloon rise up is the same Archimedes force. The Archimedean force is calculated using the formula:

Here the first term is the density of the liquid (gas), the second is the acceleration of gravity, the third is the volume of the body. If the force of gravity is equal to the force of Archimedes, the body floats, if it is greater, it sinks, and if it is less, it floats until it begins to float.

In this article we looked at Archimedes' law for dummies. If you want to learn how to solve problems where Archimedes' law is found, contact to our specialists. The best authors will be happy to share their knowledge and break down the solution to the most difficult problem “on the shelves.”

EXPERIMENTS on the topic “Archimedes’ power”

Science is wonderful, interesting and fun. But it’s hard to believe in miracles from words; you have to touch them with your own hands. There is an interesting experience!
And if you're attentive,
Independent in mind
And with physics on first hand
It's an interesting experience -
Funny, exciting -
He will reveal secrets to you
And new dreams!

1) Living and dead water

Place on the table a liter glass jar filled 2/3 with water and two glasses with liquids: one labeled “living water,” the other labeled “dead water.” Place a potato tuber (or a raw egg) into the jar. He's drowning. Add “live” water to the jar and the tuber will float; add “dead” water and it will sink again. By adding one liquid or another, you can get a solution in which the tuber will not float to the surface, but will not sink to the bottom either.
The secret of the experiment is that in the first glass there is a saturated solution of table salt, in the second - ordinary water. (Tip: before the demonstration, it is better to peel the potatoes and pour a weak salt solution into the jar so that even a slight increase in its concentration causes an effect).

2) Cartesian pipette diver

Fill the pipette with water until it floats vertically, almost completely submerged. Place the diver's pipette into a clear plastic bottle filled to the top with water. Seal the bottle with a lid. When pressing on the walls of the vessel, the diver will begin to fill with water. By changing the pressure, get the diver to follow your commands: “Down!”, “Up!” and “Stop!” (stop at any depth).

3) Unpredictable potatoes

(The experiment can be carried out with an egg). Place the potato tuber in a glass vessel half filled with an aqueous solution of table salt. He floats on the surface.
What happens to potatoes if you add water to a vessel? They usually answer that the potatoes will float. Carefully pour water (its density is less than the density of the solution and the egg) through the funnel along the wall of the vessel until it is full. Potatoes, to the surprise of the audience, remain at the same level.

4) Rotating peach

Pour sparkling water into a glass. Carbon dioxide dissolved in a liquid under pressure will begin to come out of it. Place the peach in the glass. It will immediately float to the surface and... begin to rotate like a wheel. He will behave this way for quite a long time.

In order to understand the reason for this rotation, take a closer look at what is happening. Pay attention to the velvety skin of the fruit, to the hairs of which gas bubbles will stick. Since there will always be more bubbles on one half of the peach, a greater buoyant force acts on it, and it turns upward.

5) Archimedes' force in bulk matter

At the performance “The Legacy of Archimedes,” residents of Syracuse competed in “retrieving a pearl from the bottom of the sea.” A similar but simpler demonstration can be repeated using a small glass jar of millet (rice). Place a tennis ball (or cork stopper) in there and close the lid. Turn the jar over so that the ball is at the bottom under the millet. If you create a slight vibration (lightly shake the jar up and down), then the friction force between the millet grains will decrease, they will become mobile and after a while the ball will float to the surface under the influence of the Archimedes force.

6) The package flew without wings

Place a candle, light it, hold the bag over it, the air in the bag will heat up,

After releasing the package, see how the package flies upward under the influence of Archimedes' force.

7) Different swimmers swim differently

Pour water and oil into the vessel. Lower the nut, plug and ice pieces. The nut will be at the bottom, the plug will be on the surface of the oil, and the ice will be on the surface of the water under a layer of oil.

This is explained by the floating conditions of the bodies:

Archimedes' force is greater than the cork's gravity - the cork floats on the surface,

Archimedes' force is less than the force of gravity acting on the nut - the nut sinks

the Archimedes force acting on a piece of ice is greater than the gravity of the ice - the cork floats on the surface of the water, but since the density of the oil is less than the density of water, and less than the density of ice - the oil will remain on the surface above the ice and water

8) Experience confirming the law

Hang the bucket and cylinder to the spring. The volume of the cylinder is equal to the internal volume of the bucket. The spring stretch is indicated by a pointer. Immerse the entire cylinder in a casting vessel with water. Water is poured into a glass.

The volume of water spilled out isOthe volume of a body immersed in water. The spring indicator marks the reduction in weight of the cylinder in water caused by the actionVbuoyant force.

Pour water from a glass into the bucket and you will see that the spring pointer returns to its original position. So, under the influence of the Archimedean force, the spring contracted, and under the influence of the weight of the displaced water it returned to its initial position. Archimedean force is equal to the weight of the fluid displaced by the body.

9) Balance has disappeared

Make a paper cylinder, hang it upside down on a lever and balance it.

Let's place the alcohol lamp under the cylinder. Under the influence of heat, the equilibrium is disturbed and the vessel rises. Since Archimedes' power is growing.

Suchshells filled with warm gas or hot air are called balloons and are used for aeronautics.

CONCLUSION

Having carried out experiments, we were convinced that bodies immersed in liquids, gases and even granular substances are acted upon by the Archimedes force, directed vertically upward. Archimedean force does not depend on the shape of the body, the depth of its immersion, the density of the body and its mass. The Archimedes force is equal to the weight of the liquid in the volume of the immersed part of the body.

In a physics video lesson from the Academy of Entertaining Sciences, Professor Daniil Edisonovich will talk about the ancient Greek scientist Archimedes and some of his amazing discoveries. How do you know if gold is pure? How do multi-ton ships manage to float on ocean waves? Our life is full of mysterious phenomena and tricky puzzles. Physics can provide clues to some of them. After watching the eighth physics video lesson, you will become acquainted with Archimedes' law and Archimedes' force, as well as the history of their discovery.

Archimedes' Law

Why do objects weigh less in water than on land? For a person, being in water is comparable to being in a state of weightlessness. Astronauts use this in their training. But why does this happen? The fact is that bodies immersed in water are subject to a buoyancy force, discovered by the ancient Greek philosopher Archimedes. Archimedes' law goes like this: a body immersed in a liquid loses as much weight as the volume of water it displaces weighs. The buoyancy force was called Archimedes, in honor of the discoverer. Archimedes was one of the greatest scientists of Ancient Greece. This brilliant mathematician and mechanic lived in Syracuse in the 3rd century BC. e. At this time, King Hiero ruled in Syracuse. One day, Hieron, having received the golden crown he had ordered from the craftsmen, doubted their honesty. It seemed to him that they had hidden part of the gold given for its production and replaced it with silver. But how can jewelers be caught counterfeiting? Hiero instructed Archimedes to determine whether there was an admixture of silver in the golden crown. Archimedes was constantly looking for a solution to the problem, never stopping to think about it when he was doing other things. And the solution was found... in the bathhouse. Archimedes soaped himself with ash and climbed into the bathtub. And something happened that happens every time when any person, not even a scientist, sits down in any bathtub, not even a marble one - the water in it rises. But something that Archimedes usually did not pay any attention to suddenly interested him. He stood up - the water level dropped, he sat down again - the water rose; and it rose as the body sank. And at that moment it dawned on Archimedes. He saw in the experiment performed a dozen times a hint of how the volume of a body is related to its weight. And I realized that King Hieron’s task was solvable. And he was so happy about his accidental discovery that as he was - naked, with the remains of ash on his body - he ran home through the city, filling the street with shouts: “Eureka! Eureka!". This is how Archimedes, according to legend, found the solution to Hiero’s problem. Archimedes asked the king for two ingots - silver and gold. The weight of each ingot was equal to the weight of the crown. Having placed first a silver and then a gold ingot into a vessel filled to the brim with water, the scientist measured the volume of water displaced by each ingot. Gold displaced less water than silver. And all because the volume of a piece of gold was less than a piece of silver of the same weight. After all, gold is heavier than silver. Archimedes then immersed the crown in the vessel and measured the volume of water it displaced. The crown displaced less water than a silver bar. but more than a bar of gold. So the jeweler's fraud was exposed. Thanks to Archimedes' power, giant ships weighing hundreds of thousands of tons are able to sail. This is due to the fact that they have a large displacement. That is, their volume is such that it displaces a huge amount of water. And as you remember, the larger the volume of the body, the stronger the Archimedes force acts on it.