Physical phenomena. Physical phenomena are the world around us

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1. What physics studies. Some physical terms. Observations and Experiments. Physical quantities. Measurement of physical quantities. Measurement accuracy and error.

Physics is the science of the most general properties of bodies and phenomena.

How does a person know the world? How does he investigate natural phenomena, obtaining scientific knowledge about him?

A person gets the very first knowledge from observations for nature.

To get the right knowledge, sometimes simple observation is not enough and you need to conduct experiment - specially prepared experiment .

Experiments are carried out by scientists a pre-planned plan with a specific purpose .

During experiments measurements are taken with the help of special devices for physical quantities. Examples physical quantities are: distance, volume, speed, temperature.

So, observations and experiments are the source of physical knowledge.

Physical laws are based and verified on empirically established facts. An equally important way of knowing is theoretical description of the phenomenon ... Physical theories make it possible to explain well-known phenomena and predict new ones that have not yet been discovered.

The changes that take place in bodies are called physical phenomena.

Physical phenomena are divided into several types.

Types of physical phenomena:

1. Mechanical phenomena (for example, the movement of cars, airplanes, celestial bodies, fluid flow).

2. Electrical phenomena (for example, electric current, heating of conductors with current, electrification of bodies).

3. Magnetic phenomena (for example, the effect of magnets on iron, the effect of the earth's magnetic field on the compass needle).

4. Optical phenomena (for example, reflection of light from mirrors, emission of light rays from various light sources).

5. Thermal phenomena (ice melting, water boiling, thermal expansion of bodies).

6. Atomic phenomena (for example, the operation of atomic reactors, the decay of nuclei, the processes taking place inside the stars).

7. Sound phenomena (bell ringing, music, thunder, noise).

Physical terms Are special words used in physics for brevity, definiteness, and convenience.

Physical body Is every object around us. (Showing physical bodies: pen, book, desk)

Substance is all that the physical bodies are made of. (Showing physical bodies consisting of different substances)

Matter - this is everything that exists in the Universe regardless of our consciousness (celestial bodies, plants, animals, etc.)

Physical phenomena - these are changes taking place with physical bodies.

Physical quantities are measurable properties of bodies or phenomena.

Physical devices - these are special devices that are designed to measure physical quantities and conduct experiments.

Physical quantities:
height h, mass m, path s, speed v, time t, temperature t, volume V, etc.

Physical units:

International system of units SI:

(international system)

Basic:

Length - 1 m - (meter)

Time - 1 s - (second)

Weight - 1 kg - (kilogram)

Derivatives:

Volume - 1 m³ - (cubic meter)

Speed \u200b\u200b- 1 m / s - (meter per second)

In this expression:

number 10 - numerical value of time,

the letter "s" is an abbreviation for the unit of time (seconds),

and the combination of 10 s is the time value.

Unit name prefixes:

To make it more convenient to measure physical quantities, in addition to the basic units, multiple units are used, which are 10, 100, 1000, etc. more main

g - hecto (× 100) k - kilo (× 1000) M - mega (× 1000 000)

1 km (kilometer) 1 kg (kilogram)

1 km \u003d 1000 m \u003d 10³ m 1 kg \u003d 1000 g \u003d 10³ g

We are surrounded by an endlessly diverse world of substances and phenomena.

It is constantly changing.

Any changes that occur to bodies are called phenomena. The birth of stars, the change of day and night, the melting of ice, the swelling of buds on the trees, the flashing of lightning during a thunderstorm, and so on - all these are natural phenomena.

Let's remember that bodies are made of substances. Note that under some phenomena the substances of the bodies do not change, while under others they do. For example, if you tear a piece of paper in half, then, despite the changes, the paper remains paper. If the paper is burned, it will turn into ash and smoke.

Phenomena in which the size, shape of bodies, the state of substances can change, but substances remain the same, do not turn into others, are called physical phenomena (evaporation of water, the glow of an electric bulb, the sound of the strings of a musical instrument, etc.).

Physical phenomena are extremely diverse. Among them are mechanical, thermal, electrical, light and etc.

Let's remember how clouds float across the sky, an airplane flies, a car rides, an apple falls, a trolley rolls, etc. In all these phenomena, objects (bodies) move. The phenomena associated with a change in the position of a body in relation to other bodies are called mechanical (translated from Greek "mehane" means machine, tool).

Many phenomena are caused by changes in heat and cold. In this case, changes in the properties of the bodies themselves occur. They change shape, size, the state of these bodies changes. For example, when heated, ice turns into water, water - into steam; when the temperature drops, steam turns into water, water - into ice. The phenomena associated with the heating and cooling of bodies are called thermal (fig. 35).

Figure: 35. Physical phenomenon: the transition of a substance from one state to another. If you freeze water droplets, ice will reappear

Consider electrical phenomena. The word "electricity" comes from the Greek word for "electron" - amber. Recall that when you quickly take off your wool sweater, you hear a slight crackling sound. If you do the same in total darkness, you will also see sparks. This is the simplest electrical phenomenon.

To familiarize yourself with another electrical phenomenon, do the following experiment.

Pick up small pieces of paper and place them on the table top. Comb clean, dry hair with a plastic comb and bring it up to the pieces of paper. What happened?

Figure: 36. Small pieces of paper are attracted to the comb

Bodies that, after rubbing, are capable of attracting light objects are called electrified (fig. 36). Lightning in thunderstorms, auroras, electrification of paper and synthetic fabrics are all electrical phenomena. The operation of a telephone, radio, television, and various household appliances are examples of human use of electrical phenomena.

The phenomena that are associated with light are called light. Light is emitted by the Sun, stars, lamps and some living things, such as firefly beetles. Such bodies are called luminous.

We see under the condition of exposure to light on the retina. We cannot see in absolute darkness. Objects that do not themselves emit light (for example, trees, grass, pages of this book, etc.) are visible only when they receive light from some luminous body and reflect it from their surface.

The moon, which we often speak of as a night light, is in reality only a kind of reflector of sunlight.

Studying the physical phenomena of nature, man learned to use them in everyday life, everyday life.

1. What are called natural phenomena?

2. Read the text. List what natural phenomena are called in it: “Spring has come. The sun is getting warmer. Snow melts, streams run. On the trees buds swelled, rooks flew in. "

3. What phenomena are called physical?

4. From the physical phenomena listed below, write down the mechanical phenomena in the first column; in the second - thermal; in the third - electric; in the fourth, light phenomena.

Physical phenomena: flash of lightning; snow melting; coast; melting metals; electric bell operation; rainbow in the sky; sunny bunny; moving stones, sand with water; boiling water.

The world is diverse - no matter how banal this statement may be, it really is. Everything that happens in the world is under the close scrutiny of scientists. Something they have known for a long time, something remains to be learned. Man, a curious creature, always tried to get to know the world around him and the changes taking place in it. Such changes in the surrounding world are called "physical phenomena". These include rain, wind, lightning, rainbows, and other similar natural effects.

The changes in the world around us are many and varied. Curious people could not stand aside without trying to find an answer to the question of what caused such interesting physical phenomena.

It all started with the process of observing the world around us, which led to the accumulation of data. But even a simple observation of nature evoked certain reflections. Many physical phenomena, while remaining unchanged, manifested themselves in different ways. For example: the sun rises at different times, it rains from the sky, it snows, a thrown stick flies far, then close. Why is this happening?

The emergence of such questions becomes evidence of the gradual development of human perception of the world, the transition from contemplative observation to active study of the environment. It is clear that each changing physical phenomenon manifested in different ways, this active study only accelerated. As a result, there were attempts at experimental knowledge of nature.

The first experiments looked quite simple, for example: if you throw a stick like that, will it fly far away? And if you throw the stick differently? This is already an experimental study of the behavior of a physical body in flight, a step towards establishing a quantitative relationship between it and the conditions that cause this flight.

Of course, all that has been said is a very simplified and primitive presentation of attempts to study the world around us. But, in any case, albeit in a primitive form, it makes it possible to consider the occurring physical phenomena as the basis for the emergence and development of science.

In this case, it doesn't matter what kind of science it is. At the heart of any cognition process is the observation of what is happening, the accumulation of initial data. Let it be physics with its study of the surrounding world, let it be biology, cognizing nature, astronomy, trying to cognize the Universe - in any case, the process will be the same.

The physical phenomena themselves can be different. To be more precise, their nature will be different: rain is caused by some reasons, rainbow - by others, lightning - by others. It took a very long time in the history of human civilization only to understand this fact.

The study of various natural phenomena and its laws is engaged in such a science as physics. It was she who established the quantitative relationship between the various properties of objects or, as physicists say, bodies, and the essence of these phenomena.

In the course of the study, special tools, research methods, units of measurement appeared, which allow describing what is happening. Knowledge about the surrounding world expanded, the results obtained led to new discoveries, new tasks were put forward. There was a gradual isolation of new specialties dealing with the solution of specific applied problems. This is how heat engineering, the science of electricity, optics and many, many other fields of knowledge within physics itself began to appear - not to mention the fact that other sciences appeared that dealt with completely different problems. But in any case, it must be recognized that the observation and study of the phenomena of the surrounding world allowed over time to form numerous new branches of knowledge that contributed to the development of civilization.

As a result, a whole system of studying and mastering the world, the surrounding nature and man himself has developed - from a simple observation of physical phenomena.

This material describes physical phenomena as the basis for the formation and education of science, in particular, physics. An idea of \u200b\u200bhow the development of science took place is given, such stages as observation of what is happening, experimental verification of facts and conclusions, and the formulation of laws are considered.

As a rule, very few students love the school science of natural science about the properties and structure of matter. And in fact - tedious problem solving, complex formulas, incomprehensible combinations of special characters, etc. In general, sheer gloom and melancholy. If you think so, then this material is definitely for you.

In this article we will tell you the most interesting facts about physics, which will make even a person indifferent to it look at natural science in a different way. Without a doubt, physics is a very useful and interesting science, and there are a lot of interesting facts about the Universe related to it.

1. Why is the sun red in the morning and evening? A wonderful example of a fact from physical phenomena in nature. In fact, the light of a red-hot celestial body is white. With its spectral change, a white glow tends to acquire all the colors of the rainbow for itself.

In the mornings and evenings, the sun's rays pass through numerous layers of the atmosphere. Air molecules and the smallest dry dust particles are able to delay the passage of sunlight, best of all allowing only red rays through themselves.

2. Why does time tend to stop at the speed of light? If we believe the general theory of relativity, proposed, the absolute value of the speed of propagation of electromagnetic waves in a vacuum environment is unchanged and equal to three hundred million meters per second. In fact, this is a unique phenomenon, given that nothing in our universe can exceed the speed of light movement, however, this is still a theoretical opinion.

One of the theories, authored by Einstein, has an interesting section, which says that the more you gain speed, the slower time starts to move in comparison with the surrounding objects. For example, if you drive your car for an hour, you will age slightly less than if you were just lying in your bed at home, watching TV programs. Nanoseconds are unlikely to significantly affect your life, but the proven fact remains.

3. Why does the bird sitting on the electric wire not die from the current discharge? A bird sitting on a power line is not exposed to an electric shock, because its body has insufficient conductivity. In places where the bird touches the wire, a so-called parallel connection is created. The high-voltage wire is the best current conductor; only the minimum power current moves through the body of the bird itself, which is not able to cause significant harm to the health of the bird.

But as soon as a vertebrate animal covered with feathers and down, standing on a wire, touches a grounded object, for example, with the metal part of a high-voltage power line, it instantly burns out, because the resistance in this case becomes too great, and all the electric current pierces the body of the unfortunate bird.

4. How much dark matter is in the universe? We live in the material world, and all that we can see around us is matter. We have the opportunity to touch it, sell it, buy it, we can dispose of the matter at our discretion. However, in the Universe there is not only objective reality in the form of matter, but also dark matter (physicists often talk about it as a "dark horse") - this is a type of matter that does not tend to emit electromagnetic waves and interact with them.

For obvious reasons, nobody was able to see or touch dark matter. Scientists have come to the conclusion that it is present in the Universe, more than once observing indirect evidence of its existence. It is generally accepted that its share in the composition of the Universe is 22%, while the matter familiar to us occupies only 5%.

5. Are there earth-like planets in the Universe? Undoubtedly there are! Taking into account the scale of the universe, the likelihood of this is estimated by scientists to be quite high.

However, only recently scientists from NASA began to actively discover such planets located no further than 50 light years from the Sun, called exoplanets. Exoplanets are terrestrial planets revolving around the axis of other stars. To date, more than 3,500 Earth-like planets have been found, and scientists are discovering alternative places for human existence more and more.

6. All objects fall at the same speed. It may seem to some that objects with a large weight fall down much faster than lighter ones - this is a completely logical assumption. Surely a hockey puck falls at a much faster rate than a bird's feather. In fact, this is so, but not through the fault of gravity - the main reason due to which we can observe this is that the gas shell surrounding the planet provides the most powerful resistance.

It has been 400 years since the first time I realized that universal gravitation applies to all objects in the same way, regardless of their severity. If you had the opportunity to repeat the experiment with a hockey puck and a bird's feather in space (where there is no atmospheric pressure), they would fall down at the same speed.

7. How does the northern lights appear on Earth? Throughout their existence, people have watched one of the natural wonders of our planet - the northern lights, but at the same time they could not understand what it is and where it comes from. The ancient people, for example, had their own idea: a group of indigenous Eskimo peoples believed that this was a sacred light that was emitted by the souls of deceased people, and in ancient European countries they assumed that this was military operations that defenders of their state who died in wars are forever doomed ...

The first scientists came a little closer to solving the mysterious phenomenon - they put forward the theory for worldwide discussion that the glow arises as a result of the reflection of light rays from ice blocks. Modern researchers believe that the multi-colored light is triggered by the collision of multimillion-dollar atoms and dust particles from our atmospheric envelope. The fact that the phenomenon is widespread mainly at the poles is explained by the fact that in these regions the strength of the Earth's magnetic field is especially strong.

8. Quicksands sucking in deep. The force of pulling a stuck leg out of the sands oversaturated with air and moisture of ascending sources at a speed of 0.1 m / s is equal to the force of lifting an average passenger car. Noteworthy fact: quicksand refers to a non-Newtonian fluid that is not able to absorb the entire human body.

Therefore, people who are mired in quicksand die from exhaustion or dehydration of the body, excessive ultraviolet radiation or other reasons. God forbid, you are in such a situation, it is worth remembering that it is strictly forbidden to make sudden movements. Try to tip your torso back as high as possible, spread your arms wide and wait for the rescue team to help.

9. Why is the unit for measuring the strength of alcoholic beverages and temperature called the same - degree? In the 17th-18th centuries, the generally accepted scientific principle of caloric, the so-called weightless matter, which was in physical bodies and was the cause of thermal phenomena, operated.

According to this principle, more heated physical bodies contain many times more concentrated caloric than in less heated ones, therefore the strength of alcoholic beverages was determined as the temperature of a mixture of a substance and caloric.

10. Why doesn't a drop of rain kill a mosquito? Physicists managed to find out how mosquitoes manage to fly in rainy weather and why raindrops do not kill bloodsuckers. The size of insects is the same as the size of a raindrop, but one drop weighs 50 times more than a mosquito. The impact of a drop can be equated to a passenger car or even a bus crashing into a human body.

Despite this, insects are not disturbed by rain. The question arises - why? The speed of a raindrop is about 9 meters per second. When an insect enters the shell of a drop, tremendous pressure acts on it. For example, if a person were subjected to such pressure, his body would not have withstood, but the mosquito is able to safely withstand such loads due to the specific structure of the skeleton. And to continue flying in a given direction, a mosquito just needs to shake off a drop of rain from its hairs.

Scientists say that the volume of a drop is quite enough to kill a mosquito if it is on the ground. And they attribute the absence of consequences after a rain drop hits a mosquito with the fact that the movement associated with a drop allows you to minimize the transfer of energy to the insect.

There is still an unlimited number of facts in this science. And if today famous scientists were not fond of physics, we would not know all that interesting that is happening around us. Achievements of famous physicists allowed us to understand the importance of substantiating laws-prohibitions, laws-statements and absolute laws for the life of mankind.