Physical bodies are the “actors” of physical phenomena. Let's get to know some of them.

Mechanical phenomena

Mechanical phenomena are the movement of bodies (Fig. 1.3) and their action on each other, for example repulsion or attraction. The action of bodies on each other is called interaction.

We will get to know mechanical phenomena in more detail this academic year.

Rice. 1.3. Examples of mechanical phenomena: movement and interaction of bodies during sports competitions (a, b. c); movement of the Earth around the Sun and its rotation around its own axis (g)

Sound phenomena

Sound phenomena, as the name suggests, are phenomena involving sound. These include, for example, the propagation of sound in air or water, as well as the reflection of sound from various obstacles - say, mountains or buildings. When sound is reflected, a familiar echo appears.

Thermal phenomena

Thermal phenomena are the heating and cooling of bodies, as well as, for example, evaporation (the transformation of a liquid into steam) and melting (the transformation of a solid into a liquid).

Thermal phenomena are extremely widespread: for example, they determine the water cycle in nature (Fig. 1.4).

Rice. 1.4. Water cycle in nature

The water of the oceans and seas, heated by the sun's rays, evaporates. As the steam rises, it cools, turning into water droplets or ice crystals. They form clouds from which water returns to Earth in the form of rain or snow.

The real “laboratory” of thermal phenomena is the kitchen: whether soup is being cooked on the stove, whether water is boiling in a kettle, whether food is frozen in the refrigerator - all these are examples of thermal phenomena.

The operation of a car engine is also determined by thermal phenomena: when gasoline burns, a very hot gas is formed, which pushes the piston (motor part). And the movement of the piston is transmitted through special mechanisms to the wheels of the car.

Electrical and magnetic phenomena

The most striking (in the literal sense of the word) example of an electrical phenomenon is lightning (Fig. 1.5, a). Electric lighting and electric transport (Fig. 1.5, b) became possible thanks to the use of electrical phenomena. Examples of magnetic phenomena are the attraction of iron and steel objects by permanent magnets, as well as the interaction of permanent magnets.

Rice. 1.5. Electrical and magnetic phenomena and their uses

The compass needle (Fig. 1.5, c) rotates so that its “north” end points north precisely because the needle is a small permanent magnet, and the Earth is a huge magnet. The Northern Lights (Fig. 1.5, d) are caused by the fact that electrically charged particles flying from space interact with the Earth as with a magnet. Electrical and magnetic phenomena determine the operation of televisions and computers (Fig. 1.5, e, f).

Optical phenomena

Wherever we look, we will see optical phenomena everywhere (Fig. 1.6). These are phenomena associated with light.

An example of an optical phenomenon is the reflection of light by various objects. Rays of light reflected by objects enter our eyes, thanks to which we see these objects.

Rice. 1.6. Examples of optical phenomena: The sun emits light (a); The moon reflects sunlight (b); Mirrors (c) reflect light especially well; one of the most beautiful optical phenomena - rainbow (d)

Since ancient times, people have been collecting information about the world in which they live. There was only one science that united all the information about nature that humanity had accumulated at that time. At that time, people did not yet know that they were observing examples of physical phenomena. Currently, this science is called “natural science”.

What does physical science study?

Over time, scientific ideas about the world around us have changed noticeably - there are many more of them. Natural science split into many separate sciences, including: biology, chemistry, astronomy, geography and others. In a number of these sciences, physics occupies not the last place. Discoveries and achievements in this field have allowed humanity to acquire new knowledge. These include the structure and behavior of various objects of all sizes (from giant stars to the smallest particles - atoms and molecules).

The physical body is...

There is a special term “matter”, which in scientific circles is used to describe everything that is around us. A physical body consisting of matter is any substance that occupies a certain place in space. Any physical body in action can be called an example of a physical phenomenon. Based on this definition, we can say that any object is a physical body. Examples of physical bodies: button, notepad, chandelier, cornice, Moon, boy, clouds.

What is a physical phenomenon

Any matter is in constant change. Some bodies move, others come into contact with others, and others rotate. It is not for nothing that many years ago the philosopher Heraclitus uttered the phrase “Everything flows, everything changes.” Scientists even have a special term for such changes - these are all phenomena.

Physical phenomena include everything that moves.

What types of physical phenomena are there?

• Thermal.

These are phenomena when, due to the effects of temperature, some bodies begin to transform (shape, size and condition change). An example of physical phenomena: under the influence of the warm spring sun, icicles melt and turn into liquid; with the onset of cold weather, puddles freeze, boiling water becomes steam.

• Mechanical.

These phenomena characterize a change in the position of one body in relation to the others. Examples: a clock is running, a ball is jumping, a tree is shaking, a pen is writing, water is flowing. They are all in motion.

• Electrical.

The nature of these phenomena fully justifies their name. The word “electricity” has its roots in Greek, where “electron” means “amber.” The example is quite simple and probably familiar to many. When you suddenly take off a woolen sweater, you hear a small crack. If you do this by turning off the light in the room, you can see sparkles.

• Light.

A body participating in a phenomenon associated with light is called luminous. As an example of physical phenomena, we can cite the well-known star of our solar system - the Sun, as well as any other star, a lamp, and even a firefly bug.

• Sound.

The propagation of sound, the behavior of sound waves when colliding with an obstacle, as well as other phenomena that are somehow related to sound, belong to this type of physical phenomena.

• Optical.

They happen thanks to light. For example, humans and animals are able to see because there is light. This group also includes the phenomena of propagation and refraction of light, its reflection from objects and passage through different media.

Now you know what physical phenomena are. However, it is worth understanding that there is a certain difference between natural and physical phenomena. Thus, during a natural phenomenon, several physical phenomena occur simultaneously. For example, when lightning strikes the ground, the following effects occur: sound, electrical, thermal and light.

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, moving vehicles, 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 to 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 can be converted into “dry ice” by cooling.

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 occur with the appearance, existence, movement and interaction of electrical charges (electric current, 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 the internal structure of the substance of physical bodies changes (the glow of the Sun and stars, an atomic explosion).

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1. 
   Mechanical phenomena(for example, the movement of cars, airplanes, celestial bodies, fluid flow).
2. 
   Electrical phenomena(for example, electric current, heating of current-carrying conductors, electrification of bodies).
3. 
   Magnetic phenomena(for example, the effect of magnets on iron, the influence of the earth’s magnetic field on a compass needle).
4. 
   Optical phenomena(for example, reflection of light from mirrors, emission of light rays from various light sources).
5. 
   Thermal phenomena(melting ice, boiling water, thermal expansion of bodies).
6. 
   Atomic phenomena(for example, the operation of atomic reactors, nuclear decay, processes occurring inside stars).
7. 
   Acoustic phenomena(eg echo).

1. 
   Give examples of physical phenomena: mechanical, electrical, magnetic, optical, thermal.
2. 
   Which of the following phenomena are physical?
   • 
     Force
   • 
     Ton
   • 
     Snow melting
   • 
     Molecule
   • 
     Boiling
   • 
     Time
   • 
     Walking

Lesson No. 2.
Any science uses its own special words - scientific terms. A physicist, speaking about the motion of bodies, usually does not take into account what exactly is moving, since for the study of mechanical motion this is unimportant in many problems. Therefore, in these cases we talk about the physical body.

Physical body - these are all the objects that surround us (for example, a car, a table, a mug, a doll, etc.)

Any material object (physical body) consists of matter, and we can see and touch it.

Substance- this is what all the objects around us are made of (for example, the physical body, a mug, consists of porcelain, porcelain is a substance; the physical body, a spoon, consists of aluminum, aluminum is a substance).
Exercise.

Give examples of 10 physical bodies and the substances they consist of.

Lesson No. 3
When conducting experiments, we are dealing with physical parameters that can either change over time or not. Characteristics of bodies or processes that can be changed are called physical quantities.

Physical quantities include volume, mass, length, time, speed, temperature, weight, area, etc.

Any physical quantity is measured in its own units. Usually all physical quantities are measured in the international system of units.

For example, the unit of time is the second (1s), the unit of length is the meter (1m).

To measure physical quantities they use measuring instruments. The simplest measuring instruments are a thermometer, stopwatch, ruler, etc.
Exercise.

1.Guess the riddles about physical devices:

Two sisters were rocking

They sought the truth.

And when we achieved it,

Then they stopped.

An arrow moves across the plate.

This forward arrow

He knows the weather for us.

No sleep for him, no nap.

He precisely keeps count of his steps,

But it still won’t budge.

• 
  Length, second
• 
  Time, meter
• 
  Volume, cubic meter
• 
  Temperature, millimeter

Over the course of centuries and millennia, humanity has encountered many problems that it was not always able to explain. Weather changes, the movement of celestial bodies, plant growth, the light of a flame, the change of seasons - all these processes seemed to our ancestors as mysterious mysteries of nature. Gradually, humanity came to explain the material nature of many of them: some earlier, others relatively recently. Entire branches of science have emerged that study certain natural phenomena.

What did our ancestors observe most often? The change of day and night, cold and heat, the movement of clouds and the sun across the sky, rain and thunderstorms, the blowing of wind, the germination of grain through the soil, the freezing of water and the melting of ice. Most of those observed were mechanical phenomena, that is, associated with the movement and movement of various bodies, both living and nonliving. These include the growth of grass and the movement of the moon across the sky.

Mechanical phenomena, examples of which are found everywhere, along with many others, have been studied by mankind for centuries. The initial knowledge of humanity about the world around us has grown over time into a coherent system. Entire branches of science have emerged, specializing in the study of certain processes. Physics studies mechanical phenomena, more precisely, its section called kinematics - the science of the movement and displacement of bodies. Modern concepts of kinematics are based on the postulates of Newtonian classical mechanics. They are based on a mechanistic idea of ​​the structure of the world around us, which dominated science until the beginning of the twentieth century. These ideas are completely correct and justified in terms of movements occurring at relatively low speeds (we are not talking about objects whose size is significantly smaller than the distance they travel.

In general, mechanical phenomena are a type of group of physical phenomena. Physical phenomena include those in which there is no transformation of one substance into another. In this case, it may change (water turns into ice), but it is the same substance. The phenomena of interactions of different substances with the subsequent formation of new ones is studied by another science - chemistry.

Mechanical phenomena are not the only ones in physics. In addition to them, physics studies what occurs during the emergence, movement, interaction of electric charges (electric current, lightning, telegraph), magnetic (the attraction of metal objects by a magnet, turning the compass needle to the north), optical, what occurs during the reflection and refraction of light (mirages, rainbows, reflection objects in the mirror and casting shadows), as well as thermal (melting snow, fog, boiling water) and

Of course, mechanical phenomena are among the most studied. The science that studies them - mechanics - has as its main task the determination of the location of a body in the surrounding space at any arbitrary moment in time. The motion of a body in mechanics is considered not in itself, but in relation to other bodies; one of them can be taken as the initial one when counting. Movement is considered in a coordinate system along three mutually perpendicular axes that have a common reference point.

It is also taken into account that a body can move relative to some bodies and not move relative to others. There are concepts of movement and paths traversed by bodies. Thus, mechanics, which studies the movement of bodies, considers its main task to be finding the position of the body at any moment.

The concepts of speed and time, which are necessary to determine the distance traveled, are of great importance in the study of mechanical phenomena. The science of the movement of bodies also considers different ones - translational, rotational, mixed.

Physics as a science that studies the endless variety of natural phenomena (mechanical and not only) is certainly one of the most interesting and fascinating branches of knowledge.