What is a phenomenon? Physical phenomena.
We often take for granted everything that happens to us on earth, but every minute our lives are controlled by many forces. There are a surprising number of unusual, paradoxical, or challenging physical laws that we encounter every day. In a fun exploration of physics everyone should know, we talk about common occurrences that many people consider a mystery, strange forces we can't understand, and how science fiction can become reality through light manipulation.
10. Cold wind effect
Our perception of temperature is quite subjective. Humidity, individual physiology, and even our mood can change our perception of hot and cold temperatures. The same thing happens with the wind: the temperature we feel is not real. The air that directly surrounds the human body serves as a kind of air cloak. This insulating air cushion keeps you warm. When the wind blows on you, this air cushion is blown away and you begin to feel the real temperature, which is much colder. The cool wind effect only affects those objects that produce heat.
9. The faster you go, the stronger force blow.
People tend to think linearly, mostly based on observational principles; if one raindrop weighs 50 milligrams, two raindrops should weigh about 100 milligrams. However, the forces that control the universe often show us a different result due to the distribution of forces. An object moving at 40 kilometers per hour will hit a wall with a certain force. If you double the speed of an object to 80 kilometers per hour, the impact force will increase not two, but four times. This law explains why accidents on highways are much more destructive than accidents in cities.
8. Orbit is just a constant free fall.
Satellites emerge as a notable recent application to the stars, but we rarely think about the concept of "orbit." We know in general that objects move around planets or large celestial bodies and never fall. But the reason for the appearance of orbits is surprisingly paradoxical. If you drop an object, it falls to the surface. However, if it is high enough and moving at a fast enough speed, it will swing away from the ground in an arc. The same effect prevents the earth from colliding with the sun.
7. Heat causes freezing.
Water is the most important liquid on earth. This is the most mysterious and paradoxical connection in nature. One of the little-known properties of water is, for example, that warm water freezes faster than cold. It is not yet fully understood how this happens, but this phenomenon, known as the Mpemba paradox, was discovered by Aristotle about 3,000 years ago. But why exactly this happens remains a mystery.
6. Air pressure.
IN this moment you are exposed to air pressure equal to approximately 1000 kilograms, the same as a small car weighs. This is due to the fact that the atmosphere itself is quite heavy, and a person located at the bottom of the ocean experiences a pressure of 2.3 kg per square centimeter. Our body can withstand such pressure, and it cannot crush us. However, sealed objects, such as plastic bottles, thrown from very high altitudes return to the ground in a compressed state.
5. Metallic hydrogen.
Hydrogen is the first element in periodic table, making it the simplest element in the Universe. Its atomic number 1 means it has 1 proton, 1 electron and no neutrons. Although hydrogen is known as a gas, it can exhibit some properties that are more common to metals than to gases. Hydrogen is located on the periodic table just above sodium, a volatile metal that is part of the composition of table salt. Physicists have long understood that hydrogen behaves like a metal under high pressure, like the one found on stars and in the cores of gas giant planets. Trying to make such a compound on earth requires a lot of effort, but some scientists believe they have already created small samples by applying pressure to diamond crystals.
4. Coriolis effect.
Thanks pretty large size planet, a person does not feel its movement. However, the clockwise motion of the Earth causes objects traveling in the northern hemisphere to move slightly clockwise as well. This phenomenon is known as the Coriolis effect. Since the Earth's surface moves at a certain speed relative to the atmosphere, the difference between the rotation of the Earth and the movement of the atmosphere causes an object moving north to pick up the energy of the Earth's rotation and begin to veer east. The opposite phenomenon is observed in the southern hemisphere. As a result, navigation systems must take into account the Coriolis force to avoid yaw.
3. Doppler effect.
Sound may be an independent phenomenon, but the perception of sound waves depends on speed. Austrian physicist Christian Doppler discovered that when a moving object, such as a siren, emits sound waves, they accumulate in front of the object and dissipate behind it. This phenomenon, known as the Doppler effect, causes the sound of an approaching object to become a pitch higher due to the shortening of the sound wavelengths. After the object passes by, the trailing sound waves lengthen and, accordingly, become tones lower.
2. Evaporation.
It would be logical to assume that chemicals must pass through a liquid state in the process of transitioning from a solid to a gaseous state. However, water is capable of immediately transforming from a solid to a gas under certain circumstances. Sublimation, or evaporation, can cause glaciers to disappear when the sun turns the ice into steam. In the same way, metals, such as arsenic, can turn into a gas when heated, releasing toxic gases. Water can evaporate below its melting point when exposed to a heat source.
1. Disguised devices.
Fast emerging technology turns science fiction stories into science facts. We can see objects when light of different wavelengths is reflected from them. Scientists have theorized that objects can be considered invisible when exposed to certain light. If the light around an object can be scattered, it becomes invisible to the human eye. IN Lately this theory became a reality when scientists invented a transparent hexagonal prism that scattered light around an object placed inside. When placed in an aquarium, the prism made goldfish, which floated there, invisible, and on the ground the livestock disappeared from sight. This cloaking effect works on the same principles as aircraft that cannot be detected by radar.
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Everything that surrounds us: both living and inanimate nature, is in constant motion and is constantly changing: planets and stars move, it rains, trees grow. And a person, as is known from biology, constantly goes through some stages of development. Grinding grains into flour, falling a stone, boiling water, lightning, glowing a light bulb, dissolving sugar in tea, movement Vehicle, lightning, rainbows are examples of physical phenomena.
And with substances (iron, water, air, salt, etc.) various changes or phenomena occur. The substance can be crystallized, melted, crushed, dissolved and again isolated from solution. However, its composition will remain the same.
Thus, granulated sugar can be crushed into a powder so fine that the slightest blow will cause it to rise into the air like dust. Sugar grains can only be seen under a microscope. Sugar can be divided into even smaller parts by dissolving it in water. If you evaporate water from a sugar solution, the sugar molecules again combine with each other to form crystals. But even when dissolved in water or when crushed, sugar remains sugar.
In nature, water forms rivers and seas, clouds and glaciers. When water evaporates, it turns into steam. Water vapor is water in a gaseous state. When exposed low temperatures(below 0˚C) water turns into a solid state - turns into ice. The smallest particle of water is a water molecule. A water molecule is also the smallest particle of steam or ice. Water, ice and steam are not different substances, but the same substance (water) in different states of aggregation.
Like water, other substances can be transferred from one state of aggregation to another.
When characterizing a substance as a gas, liquid or solid, we mean the state of the substance under normal conditions. Any metal can not only be melted (transformed into a liquid state), but also turned into gas. But this requires very high temperatures. In the outer shell of the Sun, metals are in a gaseous state, because the temperature there is 6000˚C. And, for example, carbon dioxide by cooling it can be turned into “dry ice”.
Phenomena in which there is no transformation of one substance into another are classified as physical phenomena. Physical phenomena can lead to a change, for example, in the state of aggregation or temperature, but the composition of the substances will remain the same.
All physical phenomena can be divided into several groups.
Mechanical phenomena are phenomena that occur with physical bodies when they move relative to each other (the revolution of the Earth around the Sun, the movement of cars, the flight of a parachutist).
Electrical phenomena are phenomena that arise with the appearance, existence, movement and interaction of electric charges ( electricity, telegraphy, lightning during a thunderstorm).
Magnetic phenomena are phenomena associated with the appearance of magnetic properties in physical bodies (the attraction of iron objects by a magnet, turning the compass needle to the north).
Optical phenomena are phenomena that occur during the propagation, refraction and reflection of light (rainbows, mirages, reflection of light from a mirror, the appearance of shadows).
Thermal phenomena are phenomena that occur during heating and cooling of physical bodies (melting snow, boiling water, fog, freezing of water).
Atomic phenomena are phenomena that occur when internal structure substances of physical bodies (glow of the Sun and stars, atomic explosion).
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About the world around us. In addition to ordinary curiosity, this was caused by practical needs. After all, for example, if you know how to lift
and move heavy stones, you will be able to build strong walls and build a house in which it is more convenient to live than in a cave or dugout. And if you learn to smelt metals from ores and make plows, scythes, axes, weapons, etc., you will be able to plow the field better and get a higher harvest, and in case of danger you will be able to protect your land.
In ancient times, there was only one science - it united all the knowledge about nature that humanity had accumulated by that time. Nowadays this science is called natural science.
Learning about physical science
Another example electromagnetic field is light. You will become familiar with some of the properties of light in Section 3.
3. Remembering physical phenomena
The matter around us is constantly changing. Some bodies move relative to each other, some of them collide and, possibly, collapse, others are formed from some bodies... The list of such changes can be continued and continued - it is not without reason that in ancient times the philosopher Heraclitus remarked: “Everything flows, everything changes.” Scientists call changes in the world around us, that is, in nature, a special term - phenomena.
Rice. 1.5. Examples of natural phenomena
Rice. 1.6. A complex natural phenomenon - a thunderstorm can be represented as a combination of a number of physical phenomena
Sunrise and sunset, a snow avalanche, a volcanic eruption, a horse running, a panther jumping - all these are examples of natural phenomena (Fig. 1.5).
To better understand complex natural phenomena, scientists divide them into a collection of physical phenomena - phenomena that can be described using physical laws.
In Fig. Figure 1.6 shows a set of physical phenomena that form a complex natural phenomenon - a thunderstorm. Thus, lightning - a huge electrical discharge - is an electromagnetic phenomenon. If lightning strikes a tree, it will flare up and begin to release heat - physicists in this case talk about a thermal phenomenon. The rumble of thunder and the crackle of flaming wood are sound phenomena.
Examples of some physical phenomena are given in the table. Take a look at the first row of the table, for example. What can be common between the flight of a rocket, the fall of a stone and the rotation of an entire planet? The answer is simple. All examples of phenomena given in this line are described by the same laws - the laws of mechanical motion. Using these laws, we can calculate the coordinates of any moving body (be it a stone, a rocket or a planet) at any point in time that interests us.
Rice. 1.7 Examples of electromagnetic phenomena
Each of you, taking off a sweater or combing your hair with a plastic comb, probably paid attention to the tiny sparks that appeared. Both these sparks and the mighty discharge of lightning belong to the same electromagnetic phenomena and, accordingly, are subject to the same laws. Therefore, you should not wait for a thunderstorm to study electromagnetic phenomena. It is enough to study how safe sparks behave to understand what to expect from lightning and how to avoid possible danger. For the first time such research was carried out by the American scientist B. Franklin (1706-1790), who invented effective remedy protection from lightning discharge- lightning rod.
Having studied physical phenomena separately, scientists establish their relationship. Thus, a lightning discharge (an electromagnetic phenomenon) is necessarily accompanied by a significant increase in temperature in the lightning channel (a thermal phenomenon). The study of these phenomena in their interrelation made it possible not only to better understand the natural phenomenon of a thunderstorm, but also to find a way for the practical application of electromagnetic and thermal phenomena. Surely each of you, passing by construction site, saw workers in protective masks and blinding flashes of electric welding. Electric welding (connection method metal parts using an electric discharge) - this is an example practical use scientific research.
4. Determine what physics studies
Now that you have learned what matter and physical phenomena are, it is time to determine what the subject of physics is. This science studies: the structure and properties of matter; physical phenomena and their relationships.
- let's sum it up
The world around us consists of matter. There are two types of matter: the substance from which everything is made physical bodies, and field.
Changes are constantly taking place in the world that surrounds us. These changes are called phenomena. Thermal, light, mechanical, sound, electromagnetic phenomena are all examples of physical phenomena.
The subject of physics is the structure and properties of matter, physical phenomena and their relationships.
- Control questions
What does physics study? Give examples of physical phenomena. Can events that occur in a dream or imagination be considered physical phenomena? 4. What substances do the following bodies consist of: textbook, pencil, soccer ball, glass, car? What physical bodies can consist of glass, metal, wood, plastic?
Physics. 7th grade: Textbook / F. Ya. Bozhinova, N. M. Kiryukhin, E. A. Kiryukhina. - X.: Publishing house "Ranok", 2007. - 192 p.: ill.
Lesson content lesson notes and supporting frame lesson presentation interactive technologies accelerator teaching methods Practice tests, testing online tasks and exercises homework workshops and trainings questions for class discussions Illustrations video and audio materials photographs, pictures, graphs, tables, diagrams, comics, parables, sayings, crosswords, anecdotes, jokes, quotes Add-onsMan lives in the natural world. You yourself and everything that surrounds you - the air, trees, river, sun - are different natural objects. Changes constantly occur with natural objects, which are called natural phenomena.
Since ancient times, people have tried to understand: how and why various phenomena occur? How do birds fly and why don't they fall? How can a tree float on water and why does it not sink? Some natural phenomena - thunder and lightning, solar and lunar eclipses - frightened people until scientists figured out how and why they occur.
By observing and studying phenomena occurring in nature, people have found application for them in their lives. Observing the flight of birds (Fig. 1), people designed an airplane (Fig. 2).
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| Rice. 1 | Rice. 2 |
Watching a floating tree, man learned to build ships and conquered the seas and oceans. Having studied the method of movement of the jellyfish (Fig. 3), scientists came up with a rocket engine (Fig. 4). By observing lightning, scientists discovered electricity, without which people today cannot live and work. All kinds of household electrical devices(lighting lamps, televisions, vacuum cleaners) surround us everywhere. Various electric tools(electric drill, electric saw, sewing machine) are used in school workshops and in production.
Scientists divided all physical phenomena into groups (Fig. 6):
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| Rice. 6 |
Mechanical phenomena- these are phenomena that occur with physical bodies when they move relative to each other (the revolution of the Earth around the Sun, the movement of cars, the swing of a pendulum).
Electrical phenomena- these are phenomena that arise during the appearance, existence, movement and interaction of electrical charges (electric current, lightning).
Magnetic phenomena- these are phenomena associated with the emergence of magnetic properties in physical bodies (attraction of iron objects by a magnet, turning the compass needle to the north).
Optical phenomena- these are phenomena that arise during the propagation, refraction and reflection of light (reflection of light from a mirror, mirages, the appearance of shadows).
Thermal phenomena- these are phenomena associated with heating and cooling of physical bodies (boiling a kettle, the formation of fog, the transformation of water into ice).
Atomic phenomena- these are phenomena that arise when the internal structure of the substance of physical bodies changes (the glow of the Sun and stars, an atomic explosion).
Observe and explain. 1. Give an example natural phenomenon. 2. To which group of physical phenomena does it belong? Why? 3. Name the physical bodies that participated in physical phenomena.