Research work in elementary school on the topic “Why don’t ships sink? Why doesn't the ship sink?

As you know, ships are made of metal and they are very heavy. Iron nails are also made from metal; compared to ships, they are light, but, nevertheless, they sink to the bottom. A why don't ships sink?

Archimedes' law in action. Archimedes' Paradox

To explain this phenomenon, it is necessary to have an understanding of Archimedes' Law: a body immersed in a liquid (or gas) is subject to a buoyancy force equal to the weight of the liquid (or gas) in the volume of the body. To verify the action of the buoyant force, it is enough to immerse yourself in a bathtub filled to the brim. The body will push some of the water upward and it will spill onto the floor. In other words, when a physical body is immersed in water, it makes room for itself by pushing out some of the water. And the water, in turn, pushes the body upward. The ships are very heavy, but their hulls have large, evenly spaced voids filled with air, which is lighter than water. As a result, the weight of the water that the ship pushes out is greater than its own weight. So the ship will not sink until it is overloaded and becomes heavier than the water it pushes out. By the way, empty rooms help the ship not to sink even with a hole in the hull below the water level. This is possible due to the fact that these voids are separated from each other by thick partitions. Even if water completely fills one cavity, the rest will remain in the same state.

Thus, in the case of a ship, the buoyant force is equal to the weight of water in the volume of that part of the ship that is immersed in water. If this force is greater than the weight of the ship, then it will float. By the way, Archimedes' paradox states that a body can float in a volume of water smaller than the volume of the body itself if its average density is less than the density of water. The manifestation of this paradox is that a massive body (that is, a swimming device) can float in a volume of water much smaller than the volume of the body itself.

Concepts of displacement and waterline

The ship does not sink because, unlike a nail, it has a displacement. Displacement- this is the amount (weight or volume) of water displaced by the underwater part of the ship's hull. The mass of this amount of water is equal to the weight of the entire vessel, regardless of its size, material and shape.

As you know, ships are designed to transport people and cargo. If it is empty, then its weight is minimal, and therefore it “settles” least in the sea. A loaded ship sinks deeper into the water. With increased load, excessive immersion in water is fraught with flooding - the vessel will go under water and drown. Therefore, on the body there is waterline - a special horizontal line on the outer side of the side, up to which a large watercraft is immersed in water at normal draft. Usually the ship above it is painted one color, and below it another. If the waterline level begins to submerge, this indicates that the vessel is overloaded or there is a hole. On the other hand, an empty ship should not be too light, since in this case its underwater part will be too small in relation to the surface. This situation is also dangerous: wind and waves can capsize the boat.

Nowadays, there are many sensors to determine the depth of a dive. And the waterline is only an auxiliary means of determining the serviceability and correct operation of ships.

Thus, iron ships are designed and built so that when submerged they displace an amount of water whose weight is equal to their weight when loaded.

Iron ball analogy

One can also imagine an explanation from the point of view of the physical relationship between mass, volume and density. Bodies whose density is less than the density of water float freely on its surface. As is known, density is inversely proportional to volume and directly proportional to mass, as reflected by the formula ρ=m/v. That is, with a constant body mass, in order to reduce density, it is necessary to proportionally increase its volume. The last statement can be represented by the following example.

An iron ball sinks in water because it has a lot of weight but a small volume. If this ball is flattened into a thin sheet, and the sheet is made into a large ball with an empty inside, then the weight will not increase, but the volume will increase significantly, which is why the iron ball will float.

The inside of the ship has many empty, air-filled rooms, and its average density is significantly less than the density of water. Therefore, it is very dangerous for a ship if the holes in it are filled with water - water is heavier than air - this will lead to an imbalance between the weight of the ship and its volume - and it will sink.

It is interesting that in tankers carrying oil there are almost no empty rooms with air, since oil itself has a density less than that of water. The same goes for timber trucks. Therefore, tankers and timber carriers are loaded to capacity so that air is not required. And vessels such as bulk carriers carrying metal and iron ore need a lot of empty space.

In the diagram: 1 - Forces to keep the ship afloat; 2 - Water pressure on board the ship.

Thus, the effect of the buoyant force depends, firstly, on the volume of the craft, and secondly, on the density of the water in which the vessel floats.

This force is greater, the greater the volume of the immersed body.

After physics - a little poetry

Ship and waves

There is a storm at sea, the ninth wave
And the waves crash against the ship.

He swam to himself, not knowing troubles,
And the waves quickly caught up.

Another moment, and two -
And there is only water in the ship.

He gradually went down
And, disappearing into the sea, he sank...

And the wind raged for a long time,
He took out the wrath of nature.

But finally the waves calmed down,
Nature became happy again.

But people won't laugh anymore
Their hearts will no longer beat...

Everything is quiet, smooth like mirrors,
But no people, no ship...

/L. Sh., 1991/

Can ships fly?

Hovercraft travel on water, but they do not submerge like regular ships. They float on a layer of air that lifts the ship above the surface of the water. Such a ship can move not only on water, but also on land.

How submarines dive and surface

The submarine has special tanks that are filled with water when submerged. The weight of the boat increases, it becomes heavier than the water and sinks down. When ascending, the tank is filled with air, which displaces water. This is shown schematically in the figure above.

This clumsy diving suit was invented more than 200 years ago. Air for the diver came from the surface through a long hose.

Thus, thanks to air, which is lighter than water, it is possible to control the immersion of bodies in water. The movement of submarines is based on this principle and for this reason ships do not sink.

Which are heavier than water, and construct airships and balloons that can float in the air. A life jacket is inflated, so it helps a person stay on the water.

Why do things float?

If you immerse a body in water, it will displace some water. The body takes the place where water used to be, and the level of the water rises. According to legend, an ancient Greek scientist (287 - 212 BC), while in a bath, guessed that a submerged body displaces an equal volume of water. A medieval engraving depicts Archimedes making his discovery. The force with which water pushes out a submerged body is called buoyant force. When it is equal to the weight of the body, the body floats and does not sink. Then the weight of the body is equal to the weight of the water displaced by it. The plastic duckling is very light, so a small pushing force is enough to keep it on the surface. The downward force (body weight) depends on the density of the body. Density is the ratio of a body's mass to its volume. A steel ball is heavier than an apple of the same size because it is denser. The particles of matter in the ball are packed more densely. An apple can float in water, but a steel ball sinks.

To prevent a body from sinking, its density must be less than the density of water. Otherwise, pushing out the water is not enough to keep the body on the surface. The relative density of a body is its density in relation to the density of water. The relative density of water is equal to one, which means that if the relative density of a body is greater than 1, it will sink, and if it is less, it will float.

Archimedes' Law

Archimedes' law states that the buoyancy force is equal to the weight of the liquid displaced by the body immersed in it. If the buoyancy force is less than the weight of the body, then it sinks; if it is equal to the weight of the body, it floats.

How ships sail

These days, ships are made of steel, which is 8 times denser than water. Ships do not sink because their overall density is less than the density of water. A ship is not a solid piece of steel (more about steel in the article ““). It has many cavities, so its weight is distributed over a large space, which leads to a low overall density. The Sea Giant is one of the largest ships in the world, weighing 564,733 tons. Due to its large size, the buoyancy force for it is very high.

If you want to see how the buoyancy force works, drop a clay ball into a vessel of water. He will drown and the water level will rise. Mark the new water level with a felt-tip pen. Now mold a boat from the same clay and carefully lower it into the water. As you can see, the water has risen even higher. The boat displaces more water than the ball, which means the buoyancy force is greater.

Load Lines

Load lines are lines drawn on the side of a ship. They show how much cargo a ship can carry under certain conditions. So, since cold water is denser than warm water, it pushes the ship harder. This means that the ship can take on board more cargo. Salt water is denser than fresh water, therefore, in fresh water the ship should be loaded less. Freight stamps were invented by Samuel Plimsoll (1824-1898). When the vessel is immersed in water to the appropriate line (see figure), it is considered fully loaded. The meaning of the letter symbols: TF - fresh water tropics, SF - fresh water in summer, T - salt water tropics, S - salt water in summer, W - salt water in winter, WNA - North. Atlantic in winter.

Aeronautics

Bodies can fly for the same reasons that they float in water. They are acted upon by the force of air pushing out. The density of air is so low that very few bodies can float in it. These are, for example, cylinders with hot air, which is less dense than cold air. Balloons can also be filled with helium or other gases that are lighter than air.

Ships and boats

Once upon a time, boats and ships floated, obeying the power of the wind or the muscular strength of man. The creation allowed shipbuilders to use propellers to push the ship through the water. Recently, hydrofoils have appeared. Great Britain (built 1843) was the first iron ship with a propeller. It was powered by a steam engine. The ship was also equipped with sails. Container ships carry cargo in large metal boxes. They can be quickly loaded onto the ship and unloaded back using cranes. One ship can take on board up to 2000 containers. Tankers also transport other liquids in tanks located in their holds. Some tankers are 20 times longer than a tennis court.

Volkov Alexander

This research work of a 1st grade student aims to understand why the ship does not sink.

Download:

Preview:

EDUCATION COMMITTEE

.

ADMINISTRATION OF THE CITY DISTRICT "CITY OF KALININGRAD"

MAOU Lyceum No. 17

Lyceum student scientific and practical conference

"Cognition and Creativity"

“Why doesn’t the ship sink?”

Research

Volkov Alexander,

student of 1st "B" class

MAOU Lyceum No. 17

Kaliningrad

Supervisor

Skapets Tatyana Vladimirovna

Kaliningrad, 2014

Target : understand why the ship does not sink.

Tasks :

1. find out which objects sink and which don’t,
2. find out what density is,
3. find out what the buoyant force of substances is,
4. find out what conditions are necessary for ships to sail.

Research methods: experiment, observation.

Practical significance: the results of the study will allow you to learn more about the world around you and help in everyday life

I once noticed that some objects sink in water, while others do not. For example, a stone thrown into the water will immediately sink to the bottom, but a piece of wood will float, or a small nail will sink, but a huge ship will not. I wondered why this was happening.

1. Will he drown or not?

To find out which objects sink and which don’t, let’s conduct an experiment.

Experiment No. 1 “Will you drown or not?”

We will need : Container with water, items to be tested.

Progress of the experiment: One by one we lower the test items into a container of water and observe what happens.

Conclusion: There are objects that are heavier than water, they sink, and there are objects that are lighter than water, they float.

1. Density of substances.

The density of a substance is a value that shows how much mass is contained in a unit volume of a given substance.

Let's imagine a kilogram of cotton wool. And immediately a fairly large lump will appear before your eyes. A kilogram of iron looks quite compact. Why do these bodies have such different volumes? It's a matter of density of matter.

All substances consist of small balls - atoms and their compounds - molecules. The closer the atoms are to each other, the denser the substance.

The next experiment will show us that the density of substances can change.

Experiment No. 2: “Water Density”

We will need : a glass of clean water (partial), a raw egg and salt.

Progress of the experiment: Place an egg in a glass; if the egg is fresh, it will sink to the bottom.

Now carefully pour salt into the glass and watch as the egg begins to float.

Why is this happening? There is an air pocket in the egg, and when the density of the liquid changes, the egg floats to the surface like a submarine.

Conclusion: Using salt we changed the density of water. The salt dissolved in the water: the molecules of water and salt mixed and the density of the water became higher than the density of the egg⇒ the egg floated to the surface.

We can also draw a conclusion about the floating conditions of the bodies:

1. If the density of a body is equal to the density of the liquid, then the body floats at any depth in the liquid.
2. If the density of the body is greater than the density of the liquid, then the body sinks in the liquid.
3. If the density of the body is less than the density of the liquid, then the body floats.

1. Archimedes' law or the buoyant force of water.

A body immersed completely or partially in a liquid is subject to a buoyant force directed vertically upward and equal to the weight of the liquid displaced by the body.

It should be noted that the body must be completely surrounded by liquid (or intersect with the surface of the liquid). So, for example, Archimedes' law cannot be applied to a cube that lies at the bottom of a container, touching the bottom tightly.

Let's do one more experiment.

Experiment No. 3 “Buoyancy depends on shape”

We will need : container with water, plasticine.

Progress of the experiment: Place a piece of plasticine in a container of water. We observe the result: the plasticine drowned.

Let's take the same piece of plasticine out of the water and give it a different shape. Now let’s put the plasticine into the water again. What happened? Plasticine floats.

Why did it happen? We gave the plasticine the desired shape and the average density of the plasticine boat (plasticine + air) became less than the density of water ⇒ plasticine floats.

Conclusion: Bodies that have been given shape, regardless of their density, will remain floating on the surface of the water.

1. How are ships built?

In the process of my research work, I found out that a body will float if the average density of all components of the body is less than the density of the liquid. I decided to try to make my own model of the ship and see if it would float on the water.

Experiment No. 4 “The ship floats!”

We will need : Water container, homemade ship.

Progress of the experiment: We lower a homemade ship into a basin of water. Let's see what happens.

So, to build a floating craft, you need to know: the floating craft must displace as much water as possible with its bottom; it is imperative to take into account the density of the material from which the boat is made (all substances less dense than water float on its surface); Water must not be allowed to get inside the ship, otherwise it will sink.

Conclusion: A steel ship does not sink because it displaces a lot of water. And we know that the more an object displaces water, the more it pushes it out. (Archimedes)

In the course of my research work, I learned a lot about the structure of bodies, density, and buoyancy.

Conclusions:

1. Based on the study, we can conclude that ships do not sink because they are acted upon by a buoyant force (Archimedes' law)
2. The ship will remain afloat as long as its weight is less than or equal to the weight of the fluid it displaces. A ship can sink if water gets inside (for example, through a hole), displacing air, and the average density of the ship becomes greater than the density of water
3. The buoyancy force depends on the density of the liquid. Consequently, in the sea, where the water is salty (with greater density), the buoyant force acting on the ship is greater than in a river or lake, where the water is fresh.

Denis Zelenov helped conduct it. 10 years.

In the summer, Denis swam on the Volga-Don Canal. I watched the large ships as they walked along the canal, rising and falling in the lock chamber. And I thought: what allows them not only to float on the water, but also to transport heavy loads?

Why can ships walk on water?

There are several reasons.

1. Density

Experience 1

We all know that if you throw a wooden board into water, it will lie on its surface, but a metal sheet of the same size immediately begins to sink.

Why is this happening? This is determined not by the weight of the object, but by its density. Density is the mass of a substance contained in a certain volume.

Experience 2

We took cubes of the same size 70x40x50 mm from different materials - metal, wood, stone and foam and weighed them. And they saw that the cubes have different weights, and therefore different densities.

Cube weight from:

• stone – 264g.,
• polystyrene foam - 3 g.,
• metal - 1020 gr.,
• wood – 70 gr.

From this they concluded that among the cubes, the densest material is metal, followed by stone, wood and foam.

Experience 3

What happens if these cubes are placed in water? As can be seen from experience, stone and metal sank - their density is greater than the density of water, but foam and wood do not - their density is less than the density of water. This means that any object will float if its density is less than the density of water.

Therefore, in order for a ship to float on water, it must be made so that its density is less than the density of water. Suppose we make it from a material that has a density less than the density of water and does not sink - for example, from wood. From history we know that people first made rafts and then boats from wood, using the property of wood - buoyancy.

Today we see many ships made of metal, but they do not sink. The reason is that their body is filled with air. Air is a much less dense substance than water. The ship develops, as it were, a total, total density of air and metal. As a result, the average density of the ship, together with the huge volume of air in its hull, becomes less than the density of water. That's why a heavy ship doesn't sink. Let us confirm this with experience.

Experience 4

Let's lower a flat sheet of metal into the water - it immediately sinks, but any vessel with sides remains afloat - a reserve of buoyancy is formed in it. You can even put a load there.

Life-saving equipment also works: a vest or circle worn by a person. With their help, it is possible to stay afloat until rescuers arrive.

2. Buoyancy force

In addition, a buoyant force acts on a body immersed in water. In the figure we see that pressure forces act on the body from all sides:

Forces acting in the horizontal direction, i.e. on board the ship, mutually compensate each other. The pressure on the lower surface - on the bottom - exceeds the pressure from above. As a result, an upward buoyant force arises.

This is clearly seen from the following experience.

Experience 5

A ball with air inside, immersed in water, flies up out of it with force.

This acts on the ball as a buoyant force (Archimedes' force). It is what keeps the ship afloat and allows the ship to float.

1-Maintenance forces; 2-Water pressure on board the vessel

What does the action of the buoyant force depend on?

First- this depends on the volume of the ship and the second - on the density of the water in which the ship floats. This force is greater, the greater the volume of the immersed body. Let's check this with experience.

Experience 6

We put a small weight on a floating board and they sink. But the volume of an inflatable boat is much larger, and it can even support several people.

Second- the buoyancy force changes with increasing water density. The density of water can be increased by salting it very, very much.

Let us prove this with the following experiment.

Since the very beginning of shipbuilding, people have put a lot of effort into trying to create ships that do not sink. The first wooden ships were lighter than water. But the development of science and knowledge of the laws of physics made it possible to build steel and even reinforced concrete ships.

Reinforced concrete ships were built in North America in the first half of the 20th century, when there was a shortage of steel during the two world wars.

The laws of physics help a ship not sink

The buoyancy of a ship is determined by Archimedes' law: a liquid pushes a body with a force equal to the weight of the liquid in the volume of the part of the body immersed in it. The main trick here is volume - the larger the volume of the ship, the thicker its metal sides can be made and the more additional cargo it can take on board while remaining afloat. This happens because the main internal volume of the ship is filled with air, which is 825 times lighter than water. It is the air that gives a ship buoyancy.

Using the same principle, submarines can submerge and surface - when submerged, the ballast tanks are filled with water, the boat loses buoyancy and sinks. When ascending, air is supplied to them under pressure, displacing water. By the same principle, a metal basin floats in the bathtub - there is air inside it, occupying most of the entire volume of the basin. If the internal volume of the basin is filled with stones or metal, it will sink because its weight will become too large.

Engineering solutions - ship stability

The buoyancy of a ship, its ability to resist the forces of wind and waves, is affected by the principle of leverage. If you throw a basin that is quietly floating in a bathtub into a river, it will soon take on water and drown, because the wind will tilt it and the waves will wash over it.

Something similar can also happen to a ship if it has low stability. There have been cases in history when hundreds of passengers gathered at one side caused the ship to roll and sink. Many ships were lost during storms because they were capsized by wind and waves.

A ship's stability is its ability to maintain a stable position in the water. It depends on the place where the ship's center of gravity is located. The closer it is to the surface, the easier it is to turn the ship over and the less stability.

That is why modern ships have the heaviest units - propulsion engines, generators, tanks with water and fuel reserves - in the lower part. The cargo holds are also located there. Sailors know that on a fully loaded ship, the motion is felt much less than on an empty one.

To shift the center of gravity as low as possible, designers specially weight the keel using lead pads. In sports vessels, a weighted keel is generally attached separately under the vessel on beams and is called an outboard keel.

Stability is also greatly influenced by the shape of the side - vessels with a semicircular bottom have the smallest, while sports trimarans, which have two outrigger hulls on the sides, have the largest. Indeed, the presence of additional supports in the upper part of the side helps maintain stability, preventing the ship from tilting. This was known in ancient times and they attached bundles of dry reeds along the top of the side of the boat. And modern tourists use inflatable cylinders for this purpose, tying them to the sides of kayaks.

Mandatory rules for a sailor

To avoid shifting the center of gravity, when loading modern ships, computer programs are used to help calculate where and how much cargo can be placed in order to maintain the seaworthiness of the vessel. The chief mate is responsible for the correct placement of cargo. He commands the loading and, in accordance with calculations, the heaviest cargoes are placed in the holds, and the lighter ones on the deck. The cargo on the ship must be “lashed”, that is, tied down. This is necessary so that during a storm it does not roll around the holds and does not change the ship’s center of gravity.

The entire hull of the ship is divided into sealed compartments. In normal condition, the partitions between the compartments are open. When a ship receives a hole, the compartment where it is located is sealed off with hermetically sealed partitions so that water cannot fill the entire hull.

During a storm, it is dangerous to turn the ship “sideways”, that is, sideways. There is too much chance that a strong wave will capsize the ship. A wave aft is also dangerous. Therefore, during severe storms, ocean-going ships often begin to move their bows against the waves, leaving the intended course - this is the safest way for a ship to survive bad weather. And only after the end of the storm do they return to the desired course.

The buoyancy and stability of a vessel are its main qualities that ensure safety. Therefore, rules that help preserve them are required to be followed. And design solutions that help improve them are always welcome.