Research work on the topic: "The force of friction". Experiments in physics. Interesting experiments in physics

The peculiarity of the pedagogical system of multi-level continuous creative education NPTM-TRIZ, which consists in the fact that the student from the object of education becomes the subject of creativity, and educational material(knowledge) from the subject of assimilation becomes a means to achieve some creative goal, until recently, was my dream as a teacher. Today, slowly but surely, the dream is becoming a reality.

To introduce an element of creativity into the lesson, to build bridges between physics and lyrics, to connect boring physical laws with the accumulated life experience of students, has always been one of the important components of my pedagogical activity. But it’s one thing to “cook” in one’s own cauldron, and another thing when at all levels of education there is continuous formation creative thinking and development creativity students, the search for highly effective creative solutions.

The German educator A. Diesterweg said: “In a few years, a student traverses the road that humanity has used for millennia. However, he should be led to the goal not blindfolded, but sighted: he should perceive the truth not as a finished result, but should discover it. The teacher must lead this expedition of discovery, and therefore also be present not only as a mere spectator. But the student must strain his strength, he should not get anything for free. It is given only to those who strive. How correctly and in unison with the requirements of the new educational Standard it is said!

With some kind of spiritual trepidation, I look forward to meeting with seventh-graders who are ready to set goals on their own, navigate situations, think creatively, act ...

But then the teacher will have to accept the Hippocratic principle “do no harm” in a new way as: help the child develop his personality, gain spiritual and moral experience and social competence.

In the Federal State Educational Standard for Basic General Education (FGOS LLC), the requirements for natural science subjects note, in particular,

Mastering the skills to formulate hypotheses, design, conduct experiments, evaluate the results;

Mastering the ability to compare experimental and theoretical knowledge with the objective realities of life.

I will show how, using the block structure of a dual creative lesson, these requirements can be implemented using the techniques and methods of NFTM-TRIZ, I will show on the example of a physics lesson in the 7th grade on the topic “Friction Force. Types of friction. Friction in nature and technology.

The principle of work is the education of personality through creativity.

The task is to create pedagogical conditions for the identification of creative abilities and their development.

I took two aphorisms as an epigraph to the lesson (although, in my opinion, they reflect the entire line of development of creative thinking and abilities, therefore they can take pride of place in the design of the office):

Man is born to think and act.

Aphorism of the ancient Greeks and Romans

Abilities, like muscles, grow with training.

Domestic geologist and geographer V. A. Obruchev (1863-1956)

Block 1. Motivation (5 min). To develop the curiosity of students at the beginning of the lesson - experience.

On the display table are two deep plates filled to the brim with water. The teacher invites two assistants to the board and invites them to participate in the experiment. Gives one student a tennis ball, another - the same rubber. Task: make the balls rotate in the water as fast as possible.

What are we seeing?

Which ball spins faster in water?

Why do you think a tennis ball spins faster than a rubber one?

The conclusion to which we come after a comprehensive analysis of the problem is that the tennis ball rotates faster than the rubber one, because its surface causes less friction with water.

Friction is the interaction that occurs when one body comes into contact with another and prevents their relative motion. And the force that characterizes this interaction is the force of friction. Today in the lesson we will reveal all the secrets of this amazing phenomenon - friction. Ready? Then get to work!

Block 2. Content (30 min)

In children on the tables: a spool of thread; elastic loop; smooth button, two matches, glue. The teacher suggests using a set of these tools to create a moving structure.

Work in groups (the teacher controls the process of search and communication activities), a demonstration of what happened and a story about how they acted:

What ideas were born?

Why stop at this one?

How was it implemented?

What problems did you face?

How were they solved? Did everything succeed?

How did it work in a team?

Possible design example:

Rice. one

1 - spool of thread;

2 - elastic loop;

3 - smooth button;

4 - a piece of a match threaded into a loop (it is better to glue it to the coil);

5 - match.

All groups worked as inventors, the result of the work of creative thought is a moving structure. The goal has been reached. The coherence of the team, the ability to listen to each other, formulate and argue their opinion and correctly defend their position played a significant role in this. But you all note that the speed of your machine is not as high as you would like.

In order to understand how to make the resulting structure faster, we need to figure out what prevents it from moving the way we want it to.

We will search in 3 directions: the cause of friction, types of friction, factors determining it. Write on the blackboard:

Reasons for friction: Types of friction: Friction depends on:

I have no doubt that there are already ideas. If you want to express your point of view, we will listen with pleasure.

We work in groups of shifts according to the scenario: idea → experience → conclusion.

Each group receives equipment for setting up experiments: a wooden block with a hook, weights, a dynamometer, a wooden board 50 × 10 cm, boards of the same size, upholstered with linoleum, rubber, round pencils. And on the interactive whiteboard - hints in the form of pictures:

Rice. 2 Fig. 3 Fig. 4

Rice. 5 Fig. 6 Fig. 7

Find pictures that show friction. Explain your point of view.

Pay attention to fig. 3, 4, 5. What do they have in common and how do they differ? (The general is friction. But at the same time, the hockey player is sliding, the cart is rolling, and the piano is standing still).

In nature and technology, there are three types of friction: rest, sliding, rolling (+ writing on the board). Try to define them. Find them in other drawings.

What causes friction force? How do you think?

Put the bar with the weight on the wooden board. Attach a dynamometer to it and, acting with a force parallel to the board, evenly move the load. Record the dynamometer readings. What force are we measuring? (traction force equal to the force of sliding friction).

Repeat the experiment on linoleum and rubber. draw conclusions
(1) one of the causes of friction is the unevenness of the contacting surfaces, which, when moving, cling to each other; 2) the friction force depends on the material of the contacting surfaces) → writing on the board.

Add a weight to the bar. Repeat experiment. Formulate a conclusion. (The force of friction is directly proportional to the force normal pressure) → writing on the board.

Place the bar with weights on the pencils. Experiment. Conclusion.

Guys, what do you know about lubrication? What is her role? What pictures is she in?

At one time, the great Italian artist and scientist Leonardo da Vinci, surprising those around him, conducted strange experiments: he dragged a rope along the floor, either in full length, or collecting it in rings. He studied: does the force of sliding friction depend on the area of the bodies in contact?

Before we know what conclusion Leonardo da Vinci came to, let's also try to answer this question. But here's an opportunity: we don't have a rope. How to be? Is it possible to get by with improvised means? We find a way out of the situation in the bar, which has different face areas. Comparing the force of sliding friction at three positions of the bar, we come to the conclusion that the force of sliding friction in all cases turned out to be the same, that is, it does not depend on the area of the bodies in contact. And what about Leonardo? (I read the answer). And here it is - the joy of knowledge!

And now I suggest that for the purpose of self-analysis of the studied material, fill in 2 tables, making up an oral story based on the resulting notes. In case of difficulty, refer to paragraphs 30 and 31 of the textbook.

Table 1

Studied physical phenomenon

table 2

The powers that I met

First you work independently, then in groups you discuss, correct, “polish” the notes.

But here it turns out that one problem arose for everyone: there is no formula for calculating the friction force in the textbook.

Guys, you already know that the force of sliding friction depends on the weight of the body and the material of the contact surfaces. The value characterizing the dependence of the friction force on the material of the contacting surfaces, their processing quality is called the coefficient of sliding friction μ. Thus, the formula for calculating the force of sliding friction: F tr = μmg.

I think that now you are ready to make your design fast, bringing it to perfection. This will be your homework. In the next lesson - the competition of your "cars". The winners get high marks. And now…

Block 3. Psychological unloading (5 min)

The boys are divided into two teams by lot, competing in tug of war. Girls are cheerleaders. They also have to explain what could be the reason for the victory or loss of the team. What type of friction and where did you encounter in this competition? Did it act as a helper or a hindrance? What would you suggest to increase the friction of the soles on the floor? hands on rope?

Block 4. Puzzle (10 min)

Tell me, guys, which of you likes to ski? My class and I sometimes spend the weekend doing this wonderful activity! True, the memories of our first campaign evoke mixed feelings in us, because. we suffered pretty much: the skis all the time “sought” to roll back, it took incredible effort to climb the smallest ascent.

What do you think was wrong with us? - Grease! And why? It would seem that skiing requires reducing friction and that's it. No, not all. When skiing ( classic style) there are two types of friction. Which? One is beneficial and needs to be increased, the other is harmful and needs to be reduced. Like this, zoom in and out at the same time! It is clear how difficult it is to find such a line that, as they say, "both the sheep were safe and the wolves were full." For each weather it has its own - this elusive line. You make a mistake - and the skis will either glide poorly or hold poorly when repelled (recoil). On this occasion, the Finns have a proverb "Skis glide on the weather."

In proverbs - short sayings, teachings - appear national history, outlook, life of people. But all this is inextricably linked with physics. Today I offer you several proverbs related to our topic (divided into groups by lot). Your task is to read the proverb and answer the questions:

What is its physical meaning?
Is the proverb true from the point of view of physics?
What is its meaning in life?

Proverbs:

Things went like clockwork (Russian).

Skis glide according to the weather (Finnish).

It is difficult to weave a network from a waxed thread (Korean).

You can't hold an eel in your hands (French).

If you don't grease, you won't go (French).

Bypassed the watermelon peel, and slipped on the coconut one (Vietnamese).

Mow the scythe while the dew; dew down, and we are home (Russian).

Block 5. Intellectual warm-up (15 min)

Today, my young physicists, I will tell you the tale "Turnip" about the static friction force, the mechanism of its occurrence, magnitude and direction. Listen carefully, because at the end you will have to answer 10 questions easier than "steamed turnips".

So listen.

Grandfather planted a turnip. A turnip has grown big, big, heavy, heavy, it has grown in all directions, it has pressed the ground. That is why her tuber had a very tight contact with the soil, the earth penetrated into all the smallest cracks and ledges. Grandfather went to pick a turnip. Pulls, pulls, can't pull. He lacks strength: the turnip rests, clings to the ground with irregularities and protrusions, resists his movement. In some places, the gap between the turnip and the soil areas is of the order of the radius of action of molecular forces. There, the adhesion of soil particles to the turnip occurs, it prevents the turnip from moving relative to the ground.

Grandpa called grandma. The grandmother pulled the grandfather, the grandfather pulled the turnip, they pulled, pulled, they couldn’t pull it out: the firmly thickened, rounded root held in the ground. Gravity pushes him to the ground. No, they can't do it together.

The grandmother called her granddaughter. The granddaughter pulls the grandmother, the grandmother pulls the grandfather, the grandfather pulls the turnip, they pull, they pull, they cannot pull: their total traction force is still less than the limiting force that arises along the contact surface of the turnip with the ground. It is called the static friction force. Caused by an external force, but always against the external force and directed. This force is ambiguous - many-sided. It can change over a wide range: from zero to a certain maximum value ... Apparently, this has not yet come maximum value.

Granddaughter called Zhuchka. The bug with four paws rested on the ground. Between the paws and the ground, too, the static friction force arises. This power helps the Bug in the same way as grandfather, grandmother and granddaughter. Without this force, they would not be able to rest, they would slide along the ground, slip. A bug for a granddaughter, a granddaughter for a grandmother, a grandmother for a grandfather, a grandfather for a turnip, they pull, pull - they cannot pull it out. But in fact, the turnip has already moved by microns. The magnitude of these micro displacements is proportional to the applied force and depends on the properties of the soil itself. And the sticking of the turnip with the ground and the elastic deformation of the shift of the soil and micro protrusions of the turnip itself, when trying to stretch it, lead to an increase in the soil elasticity force. And this emerging force of soil elasticity, in essence, is the force of static friction. She does not give any way to pull the turnip.

Bug called the cat. The cat for the Bug, the Bug for the granddaughter, the granddaughter for the grandmother, the grandmother for the grandfather, pull-pull - they can’t pull: just a little, but still less external force turned out to be than the maximum possible meaning static friction force.

The cat called the mouse. A mouse for a cat, a cat for a bug, a bug for a granddaughter, a granddaughter for a grandmother, a grandmother for a grandfather, pull-pull - they pulled out a turnip.

Just do not think that the little mouse turned out to be the strongest of all! How many of those forces a little mouse has! But its small force was added to the total traction force, and now the resulting force even somewhat exceeded the maximum value of the static friction force: the sliding friction force has become greater. Irreversible relative displacements have arisen. The "living chain" - from grandfather to mouse - pulled out a turnip, but she herself ... fell! The applied force is greater than the sliding friction force of the turnip on the ground. That's the side of greater strength, and all fell. But that's... another story.

And now the promised questions are simpler than “steamed turnips”:

Block 6. Content (15 min)

A little more and you will know everything about the force of friction.

Independent work with the textbook: study § 32, structure the text (diagram, table, etc.), discuss in a group and most good option present to the whole class by defending it. The work will be evaluated according to the following criteria: an interesting form of presentation, the competence of the defender (a clear, understandable explanation, the ability to interest the audience, reasonably answer questions asked, if any), group support. In the presentation of the result of the activity, answers to three questions should be heard: “Why am I doing it?”, “What am I doing?” and "How do I do it?"

Block 7. Computer intelligent support (10 min)

Video fragment of the cartoon "The Bremen Town Musicians" (They go, they sing "There is nothing better in the world than wandering friends around the world").

Rice. 8 Fig. nine

Find everything that is relevant to our topic, argue your choice. But it must be imagined through the "eyes" of a physicist. One starts the story, the second takes over, then the third, etc. If necessary, we repeat the cartoon, stopping at the request of the respondent.

Block 8. Resume (5 min)

“Take your “photo” of a lesson or work”

Imagine that each of you is a photographer, and you need to take some snapshots of a lesson or the activity that you just did. The photo can be color or black and white. A color freeze frame reflects something that you liked that brought you joy from what you saw, heard, performed, constructed, etc. A black and white “freeze frame” should show what you didn’t like, failed, upset.

Everyone imitates how he takes his picture: he holds a camera in his hands, releases the shutter and loudly comments on the frame, explaining why he liked or disliked something. Then the camera must be transferred to another student.

The last few “freeze frames” are taken by the teacher.

Zinovkina M. M., Utemov V. V. The structure of a creative lesson for development creative personality students in pedagogical system NFTM-TRIZ // Socio-anthropological problems information society. Issue 1. - Concept. - 2013. - ART 64054. - URL: http://e-koncept.ru/teleconf/64054.html
federal state educational standard basic general education. - URL: http://minobrnauki.rf]
Experience "Friction" - Lessons of magic. - URL: http://lmagic.info/friction.html
Balashov M. M. About nature: Book. for students in grade 7 - M.: Enlightenment. 1991. -64 p.: ill.
Teaching physics that develops the student. - Prince. 2. - Development of thinking: general ideas, training in mental operations / comp. and ed. E. M. Braverman. Handbook for teachers and methodologists. - M.: Association of Teachers of Physics. 2005. - 272 p.; ill. - (Person-centered learning.)
Cool physics. - URL: http://class-fizika.narod.ru/
Peryshkin A. V. Physics. Grade 7: textbook. for general education institutions. - 8th ed., stereotype. - M.: Bustard, 2004. - 192 p.: ill.
Tikhomirova S.A. Physics in proverbs, riddles and fairy tales. - M.: School Press, 2002. - 128 p. - (Library of the journal "Physics at School"; Issue 22)
Physics lesson in modern school: Creative. search for teachers: Book. for the teacher / comp. E. M. Braverman; ed. V. G. Razumovsky. - M.: Enlightenment, 1993. - 288 s
Teaching physics that develops the student. Book. 1. Approaches, components, lessons, tasks / comp. and ed. EM. Braverman: A guide for teachers and methodologists. - M.: Association of Teachers of Physics. 2003. - 400 p.; ill. - (Person-centered learning.)

Description of the presentation Research project in physics Friction force Purpose: by slides

Purpose: to find out what role the friction force plays in our life, how a person received knowledge about this phenomenon, what is its nature. Objectives: to trace the historical experience of man in the use and application of this phenomenon: to find out the nature of the phenomenon of friction, the laws of friction; conduct experiments confirming; regularities and dependences of the friction force; to think and create demonstration experiments proving the dependence of the friction force on the force of normal pressure, on the properties of the contacting surfaces, on the speed of the relative motion of bodies.

Report of a group of theorists Purpose: to show what role the phenomenon of friction or its absence plays in our life; answer the question: “What do we (the inhabitants) know about this phenomenon? »

The group studied proverbs, sayings, fairy tales, in which the force of friction, rest, rolling, sliding is manifested, studied human experience in the application of friction, ways to deal with friction. Proverbs and sayings: You go quieter, you will continue. You love to ride, love to carry sleds. He lies that he sews with silk. Fairy tales: "Turnip" - the friction of peace. "Chicken Ryaba" - static friction "Bear Hill" - sliding friction.

Friction is a phenomenon that has accompanied us since childhood, literally at every step, and therefore has become so familiar and invisible.

Friction enables us to walk, sit, work without fear that books and notebooks will fall off the table, that the table will slide until it hits a corner, and the pen slips out of our fingers.

However, a little friction on ice can be successfully used technically. Evidence of this is the so-called ice roads, which were arranged for the removal of timber from the felling site to railway or to fusion points. On such a road, which has smooth ice rails, two horses pull a sleigh loaded with 70 tons of logs.

Here are the data that we were told in the hospital; the number of those who applied for medical assistance in December - January, only schoolchildren, aged 15-17 years - 6 people. Mostly diagnoses: fractures, dislocations, bruises. There are elderly people among those who applied for help. 3 21 2 15 years old 16 years old 17 years old Old age

Data from the traffic police on traffic accidents for winter period: number of accidents, including those due to slippery roads —

The group also conducted a small sociological survey of a group of residents, who were asked the following questions: 1. What do you know about friction phenomena? 2. How do you feel about ice, slippery sidewalks and roads? 3. What are your suggestions to the administration of our district?

Report of a group of theorists Objectives: to study the nature of friction forces; to investigate the factors on which friction depends; consider the types of friction.

Friction Force If we try to move a cabinet, we immediately see that it is not so easy to do it. His movement will be hindered by the interaction of the legs with the floor on which he stands. There are 3 types of friction: static friction, sliding friction, rolling friction. We want to find out how these species differ from each other and what do they have in common?

Friction of rest Let's press our hand to the notebook lying on the table and move it. The notebook will move relative to the table, but rest in relation to our palm. How did we make this notebook move? With the help of rubbing the rest of the notebook against the hand. Friction at rest moves loads on a moving conveyor belt, prevents shoelaces from untying, keeps nails driven into a board, etc.

What causes the sled that rolls down the mountain to stop gradually? due to sliding friction. Why does a puck sliding on ice slow down? Due to sliding friction, always directed in the direction opposite to the direction of movement of the body. Sliding friction

Causes of the friction force: The roughness of the surfaces of the contacting bodies. Even those surfaces that look smooth, in fact, always have microscopic irregularities (protrusions, depressions). When one body slides over the surface of another, these irregularities engage with each other and thereby interfere with the movement. Intermolecular attraction acting at the points of contact between rubbing bodies. There is attraction between the molecules of a substance at very small distances. Molecular attraction is manifested in those cases when the surface of the contacting bodies is well polished. So, for example, with the relative sliding of two metals with very clean and even surfaces, processed in a vacuum using a special technology, the friction force between the wood bars with each other, and further sliding becomes impossible.

Rolling friction If a body does not slide on the surface of another body, but, like a wheel or a cylinder, rolls, then the friction that occurs at the point of their contact is called rolling friction. The rolling wheel is somewhat pressed into the roadbed, and then all the time there is a small tubercle in front of it, which must be overcome. It is precisely the fact that the rolling wheel constantly has to run into the tubercle that appears in front, and the rolling friction is due. At the same time, the harder the road, the less rolling friction. For equal loads, the rolling friction force is much less than the sliding friction force.

But the knowledge about the nature of friction did not come to us by itself. This was preceded by a large - research work of scientists experimenters. over the course of several centuries Not all knowledge took root easily and simply many required multiple experimental checks. evidence The brightest minds of recent centuries have studied the dependence of the friction modulus on: many factors on the contact area, surfaces on the type of material on the load on, surface irregularities and roughness on. relative speed of movement of bodies The names of these:, scientists Leonardo da Vinci Amonton Leonard Euler -, Charles Coulomb is the most famous names but were. , still ordinary workers of science All the scientists who participated in these studies set up experiments in which work was done to overcome the force. friction

Leonardo da Vinci He dragged along the floor either a tightly twisted rope, or the same rope in its entire length. He was interested in the answer to the question: does the force of sliding friction depend on the size of the area of bodies in contact in motion? The mechanics of that time were deeply convinced that the larger the contact area, the greater the friction force. They reasoned something like this: the more such points, the greater the force. It is quite obvious that on a larger surface there will be more such points of contact, so the friction force should depend on the area of the rubbing bodies.

He got the following results: 1. Does not depend on the area. 2. Does not depend on the material. 3. It depends on the magnitude of the load (in proportion to it). 4. Does not depend on sliding speed. 5. Depends on surface roughness.

The French scientist Amonton As a result of his experiments, he answered the same five questions in this way. For the first three - the same, for the fourth - it depends. On the fifth - does not depend. It turned out, and Amonton confirmed such an unexpected conclusion by Leonardo da Vinci about the independence of the friction force from the area of the bodies in contact. But at the same time, he did not agree with him that the force of friction does not depend on the speed of sliding; he believed that the sliding friction force depends on the speed, but he did not agree with the fact that the friction force depends on the surface roughness.

Russian Academy of Sciences Leonhard Euler Full member of the Russian Academy of Sciences Leonhard Euler published his answers to five questions about friction. The first three are the same as the previous ones, but in the fourth he agreed with Amont, and in the fifth - with Leonardo da Vinci.

French physicist Coulomb He experimented on shipyard, in one of the ports of France. There, he found those practical production conditions in which the friction force played a very important role. Coulomb answered all questions - yes. The total friction force to some small extent still depends on the dimensions of the surfaces of the rubbing bodies, is directly proportional to the normal pressure force, depends on the material of the contacting bodies, depends on the sliding speed and on the degree of smoothness of the rubbing surfaces. In the future, scientists became interested in the question of the effect of lubrication, and types of friction were identified: liquid, clean, dry and boundary.

Correct answers The force of friction does not depend on the area of the bodies in contact, but depends on the material of the bodies: the greater the force of normal pressure, the greater the force of friction. Precise measurements show that the modulus of the sliding friction force depends on the modulus of the relative velocity. The friction force depends on the quality of the processing of rubbing surfaces and the increase in the friction force as a result. If the surfaces of the bodies in contact are carefully polished, the number of points of contact with the same force of normal pressure increases, and consequently, the friction force also increases. Friction is associated with overcoming molecular bonds between contacting bodies.

In an experiment with a tribometer, the normal force. pressure is the weight of the bar Let's measure the force of normal pressure equal to the weight of the cup with weights at the moment of uniform sliding. bar Let us now increase the strength of the normal, . double pressure by placing weights on the bar, Putting additional weights on the cup again. let's make the block move evenly. In this case, the friction force will double. On the basis of such experiments, it was found that with the material and condition of the rubbing surfaces unchanged, their friction force is direct, . . : proportional to the force of normal pressure t e F tr =µ N

The value characterizing the dependence of the friction force on the material and the quality of processing of rubbing surfaces is called. friction coefficient

Friction forces in technology and everyday life. play huge role In some cases, friction forces, -. benefit others harm Friction force, ; holds driven nails screws nuts, . . keeps the threads in the matter tied knots, etc. In the absence of friction, it would not be possible to sew,. assemble clothes machine put together a box

The presence of static friction allows a person to move on the surface of the Earth. Walking, a person pushes the Earth back from himself, and the Earth pushes the person forward with the same force. Force, driving man forward, equal to the static friction force between the sole of the foot and the Earth. How stronger man pushes the Earth back, the greater the static friction force applied to the leg, and the faster the person moves. When a person pushes the Earth away with a force greater than the ultimate static friction force, the foot slides backwards, making walking difficult. Remember how hard it is to walk on slippery ice. To make it easier to walk, it is necessary to increase the static friction. For this purpose, the slippery surface is sprinkled with sand.

REPORT OF THE GROUP OF EXPERIMENTERS: The purpose is to find out the dependence of the friction force: sliding on the following factors - ; from the load - from the area of contact of the rubbing; surfaces - (from rubbing materials when dry). surfaces: Equipment laboratory dynamometer 40 / ; with spring stiffness N m dynamometer (- 12); round demonstration limit H - 2; ; wooden bars pieces set of cargo; a wooden plank a piece of metal; ; ; . sheet flat iron bar ice rubber

Experimental results: 1. Dependence of the sliding friction force on the load m (g) 120 620 1120 F tr (N) 0.3 1.5 2,

2. Dependence of the friction force on the contact area of the rubbing surfaces. S (cm 2) 220 228 1140 F tr (N) 00, 35 00,

3. The dependence of the friction force on the size of the irregularities of the rubbing surfaces: wood on wood (various methods of surface treatment). h 1 uneven 2 smooth 3 polished F tr 1, 5 0, 7 0,

1. Uneven surface - the bar is not processed. 2. Smooth surface - the bar is planed along the grain of the wood. 3. Sanded smooth surface treated with sandpaper. 4. When applying the friction force from the materials of rubbing surfaces, we use one bar weighing 120 g and different contact surfaces. We use the formula: F tr \u003d µ N No. p / p Rubbing materials (with dry surfaces) Friction coefficient (during movement) 1 Wood on wood (on average) 0.3 2 Wood on wood (along the fibers) 0.075 3 Wood for metal 0.4 4 wood for cast iron 0.5 5 wood for ice 0,

No. 1 Experience, . Carefully rub the bow with rosin and then run it along the string. Continuous singing sounds are obtained due to friction. When the violinist begins to lead the bow along the string, the string is under the influence of force. rest friction is carried away by the bow and arches under this tension. seeks to return it to its original position. When this force exceeds the static friction force, the string breaks and comes into oscillation, the violinist moves the bow in the opposite direction a. then towards. , The violin sings If you play the violin without a bow, pulling the strings, ; with fingers you get a sound like a balalaika if you pull a string with your finger,. and let go of it, then a sharp sound will be heard that quickly fades? Why rub the bow with rosin Does rosin play the role of a lubricant? , friction It turns out that the bow is rubbed with rosin not only in order to increase the friction force, but also so that this force noticeably depends on the sliding speed, it would decrease faster with growth. . speed The string under the bow always moves slower than the bow When, . bow and string move in the same direction string lags behind the bow Force. friction prevents lagging and drags the string behind the bow Force, friction does work, the bow drags the string along with it and vice versa, . slows down the string slowing down its movement Work is done against the forces. friction

No. 2 Experience wooden egg with a thread passed through the middle. They take the ends of this thread in their hands, and raise one hand high up. A wooden egg on a thread quickly slides down. Raise the other hand up. The egg rushes down again, but suddenly gets stuck in the middle of the thread, then slips again and stops. In this experiment, the sliding friction force is proportional to the normal pressure force. The egg consists of two connecting halves. A cork plug is fixed in the center perpendicular to the thread. When the thread is pulled, the friction force of the thread on the cork increases and the egg freezes in a certain position on the thread. If the thread is not taut, then the friction force is less and the egg slides freely down.

No. 3 Experience Wooden ruler. Lay the ruler horizontally index fingers hands and, slowly, the fingers begin to pull together. The ruler does not move evenly across two fingers at once. She slides in turn on one, then on the other finger. Why? Only the finger that is further from the center of mass of the ruler slides under the ruler, since it experiences less load and less friction. Its sliding stops as soon as it is closer to the center of mass of the ruler than the second finger, and then the second finger begins to slide. So the fingers move towards the center of gravity of the ruler alternately.

Conclusions based on the results of work on the project We found out that a person has long been using knowledge about the phenomenon of friction, obtained empirically. Starting from the XY - XYI centuries, knowledge about this phenomenon becomes scientific: experiments are carried out to determine the dependence of the friction force on many factors, regularities are found out. Now we know exactly what the friction force depends on and what does not affect it. More specifically, the friction force depends on: the load or body mass; from the kind of contacting surfaces; on the speed of the relative motion of bodies; on the size of irregularities or surface roughness. But it does not depend on the area of \u200b\u200bcontact. Now we can explain all the regularities of the structure of matter observed in practice by the force of interaction between molecules. We conducted a series of experiments, did about the same experiments as the scientists, and got about the same results. It turned out that experimentally we confirmed all the statements made by us. We have created a number of experiments that help to understand and explain some of the "difficult" observations. But, perhaps most importantly, we realized how great it is to acquire knowledge ourselves, and then share it with others.

The text of the work is placed without images and formulas.
Full version work is available in the "Files of work" tab in PDF format

Introduction

Winter - favorite time many kids of the Kama region! After all, you can slide down the hill with a breeze, quietly drive along the fabulous winter forest and have fun skating with friends. I love winter fun too!

Problem: to understand what prevented me from going so far without ice.

Target this project : unraveling the mystery of the force of friction.

Tasks:

trace the historical experience of mankind in the use and application of this phenomenon;

find out the nature of the friction force;

conduct experiments confirming the regularities and dependences of the friction force;

to understand where a student of the 2nd grade can meet with the force of friction;

To achieve our goals, we worked on this project in the following areas:

1) Research of public opinion;

2) The study of theory;

3) Experiment;

4) Design.

Hypothesis: the force of friction is essential in people's lives.

Scientific interest lies in the fact that in the process of studying this issue, some information was obtained about practical application friction phenomena.

1 . What is friction (a little theory)

Goals: study the nature of friction forces.

Friction force

Why so snow slide is it better to go on ice? How does the car accelerate, and what force slows it down when braking? How are plants held in the soil? Why is a live fish difficult to hold in your hand? How to explain the danger of ice in the winter? It turns out that all these questions are about the same thing!

The laws of friction provide answers to these and many other questions related to the motion of bodies. From the above questions it follows that friction is both a harmful and beneficial phenomenon.

Any body, moving along the surface, catches on its irregularities and experiences resistance. This resistance is called friction force. Friction is determined by surface properties solids, but they are very complex and have not yet been fully explored.

If we try to move the closet, we will immediately see that it is not so easy to do it. His movement will be hindered by the interaction of the legs with the floor on which he stands. What determines the amount of friction force? Everyday experience shows that the more strongly the surfaces of bodies are pressed against each other, the more difficult it is to cause their mutual sliding and to maintain it. We will try to prove this experimentally.

1.1 Role of friction forces

Let's imagine that one day something strange happened on Earth! Let's turn to thought experiment, let's imagine that in the world some wizard managed to turn off the friction . What would it lead to?

Firstly, we would not be able to walk, the wheels of cars would spin in place to no avail, clothespins would not be able to hold anything ...

Secondly, the causes that generate friction would disappear. During the sliding of one object over another, it is as if the microscopic tubercles are meshing with each other. But if these tubercles did not exist, this would not mean that it would be easier to move an object or drag it. There would be a so-called STICKING effect, which is easy to detect when trying to move a stack of books in a glossy cover along the surface of a polished table.

This means that if there were no friction, there would not be these tiny attempts of each particle of matter to keep its neighbors around. But then how would these particles stick together? That is, inside the various bodies the desire to “live in a company” would disappear, and the substance would fall apart to the smallest detail, like a LEGO house.

Here are some unexpected conclusions that can be reached if we assume the absence of friction. As with everything that hinders us, we must fight it, but it will not be possible to completely get rid of it, and it is not necessary!

In technology and in everyday life, friction forces play a huge role. In some cases, friction forces are beneficial, in others they are harmful. The force of friction holds driven nails, screws, nuts; holds threads in matter, tied knots, etc. In the absence of friction, it would be impossible to sew clothes, assemble a loom, put together a box.

Friction increases the strength of structures; without friction, neither the laying of the walls of a building, nor the fixing of telegraph poles, nor the fastening of parts of machines and structures with bolts, nails, screws can be carried out. Without friction, plants could not be held in the soil. The presence of static friction allows a person to move on the surface of the Earth. Walking, a person pushes the Earth back from himself, and the Earth pushes the person forward with the same force. The force that moves a person forward is equal to the static friction force between the sole of the foot and the Earth.

The more a person pushes the Earth back, the greater the friction force applied to the leg, and the faster the person moves.

It is very difficult to walk and drive in icy conditions because there is very little friction. In these cases, sand is sprinkled on the sidewalks and chains are put on the wheels of cars to increase the rest friction.

The force of friction is also used to keep bodies at rest or to stop them if they are moving. The rotation of the wheels is stopped by the brakes. The most common are air brakes that are powered by compressed air.

2. Design work and conclusions

Goals: create a demonstration experiment; explain the results of the observed phenomena.

After studying the literature, my dad and I made several experiments. We thought through the experiments, and tried to explain their results.

Experience #1

Let's go back to the story of my downhill ride.

Once, my dad and I were skating down an ice slide. At first I moved out without ice. And I managed to get only to the end of the ice slope. Then I decided to get out on a plastic ice rink, and my distance almost doubled!

Now, I understand that the force of friction the first time I rolled was greater, it made my body slow down faster. But even in this experiment, the hardness of the bodies matters. My winter suit is much softer than a plastic ice cap. This means that the suit interacts more with the slide and produces a greater friction force. Rigid ice is less "engaged" with the slide, and friction is less!

Experience #2

On a piece of cardboard one toothpick wide, and two toothpicks long, with plasticine, attach a toothpick across the cardboard in the middle. Then fold the edges of the cardboard. Draw a spider on colored paper. We draw a spider so that its body is larger than a rectangle. Glue a piece of cardboard to the back of the spider. Cut the thread to the length of your hand. We will thread the needle and stretch it through the cardboard. Pull the thread with the spider and hold it vertically. Then loosen the thread a little. How will the spider behave?

When the thread is pulled tight, it touches the toothpick and FRICTION occurs between them. Friction keeps the spider from sliding down.

Experience No. 3

This experiment shows what the friction force depends on.

Let's take a sheet of paper. Let's put it between the pages of a thick book lying on the table. Let's try to pull out the sheet. Let's do the experiment again. Now let's put the sheet almost at the very end of the book. Let's try to pull it out again. Experience shows that it is easier to pull a sheet from the top of a book than from the bottom. This means that the stronger the surfaces of bodies are pressed against each other, the greater their interaction, that is, the greater the friction force.

Experience No. 4

With repeated unbending and bending of the wire, the bending point heats up. This is due to friction between the individual layers of metal. Also, when rubbing a coin against a surface, the coin heats up.

Experience No. 5

This simple experiment shows the application of the force of friction.

Sharpening knives in workshops. When a knife becomes dull, it can be sharpened with a special device. The phenomenon is based on the smoothing of the notches between the contacting surfaces.

The results of these experiments can explain many phenomena in nature and human life. Now that the secret of the force of friction has become known to me, I understand that it is also described in many fairy tales! This was another discovery for me!

I really want to give examples of fairy tales. In the fairy tale "Gingerbread Man" - the force of friction helps the main character to get out of difficult situations(“Kolobok lay down, lay down, took it and rolled - from the window to the bench, from the bench to the floor, along the floor to the door, jumped over the threshold - and rolled into the canopy ...”). In the fairy tale "Ryaba the Hen" - the lack of friction force led to trouble ("The mouse ran, wagged its tail, the testicle rolled, fell and broke). In the fairy tale "Turnip" - the friction of turnips on the surface of the earth made the whole family rally. The Snow Queen with her magic, she easily overcame the force of friction (“The sleigh drove around the square twice. Kai quickly tied his sledge to it and rolled it”).

Interesting to look at famous works otherwise!

3. Public opinion survey

Goals: show what role the phenomenon of friction or its absence plays in our life; answer the question: “What do we know about this phenomenon?”

Proverbs and sayings were studied, in which the friction force of rest, rolling, sliding is manifested, human experience was studied in the application of friction, ways to combat friction.

Proverbs and sayings

There will be no snow, there will be no trace.

A quiet cart will be on the mountain.

Difficult to swim against the water.

You love to ride, love to carry sleds.

Patience and work will grind everything.

From that, the cart sang that it had not eaten tar for a long time.

And scribbles, and rolls, and strokes, and rolls. And all with language.

He lies that he sews with silk.

All these proverbs indicate that people have noticed the existence of friction forces for a long time. The people reflect in proverbs and sayings the efforts that must be made to overcome the forces of friction.

Take a coin and rub it on a rough surface. We will feel resistance - this is the force of friction. If you rub faster, the coin will begin to heat up, reminding us that heat is released during friction - a fact known to man of the Stone Age, because it was in this way that people first learned to make fire.

Friction enables us to walk, sit, work without fear that books and notebooks will fall off the table, that the table will slide until it hits a corner, and the pen slips out of our fingers.

Friction is not only a brake on movement. This is also the main reason for the wear and tear of technical devices, a problem that man also faced at the very dawn of civilization. During excavations of one of the most ancient Sumerian cities - Uruk - the remains of massive wooden wheels, which are 4.5 thousand years old, were found. The wheels are studded with copper nails, with the obvious purpose of protecting the convoy from rapid wear.

And in our era, the fight against wear of technical devices is the most important engineering problem, successful solution which would save tens of millions of tons of steel, non-ferrous metals, sharply reduce the production of many machines and spare parts for them.

Already in antiquity, engineers had at their disposal such important means for reducing friction in the mechanisms themselves as a replaceable metal bearing lubricated with grease or olive oil.

Of course, friction plays a positive role in our life. No body, whether it be the size of a stone block or a grain of sand, will ever rest on one another, everything will slide and roll. If there were no friction, the Earth would be without irregularities, like liquids.

I learned so many interesting and new things about the secrets of the force of friction. You need to fight it wisely in order to develop unprecedented speed. I decided to tell my classmates about how to ride the slides correctly and safely.

Winter is a time of fun and fun games. Skiing is everyone's favorite winter fun. Speed, the whistle of a fresh wind, a storm of overflowing emotions - in order for your vacation to be not only pleasant, but also safe, you should think about choosing both slides and sleds.

1. With a baby under 3 years old, you should not go to a busy hill with which children 7-10 years old and older ride.

2. If the slide causes you concern, first let an adult ride it, without a child - experience the descent.

3. If a child is already riding a “busy” slide of different ages, an adult must be sure to follow him. It is best if one of the adults watches the descent from above, and someone from below helps the children quickly clear the way.

4. Under no circumstances should railway embankments and hills near the carriageway of motorways be used as slides.

Rules of conduct on a busy mountain:

Climbing a snow or ice slide should only be done at a climbing point equipped with steps; it is forbidden to climb a hill where others slide down towards you.

Do not move out until the previous descender has moved aside.

Do not linger below when you have moved out, but quickly crawl away or roll to the side.

Do not cross the icy path.

To avoid injury, you can not ride while standing on your feet and squatting.

Try not to slide backwards or head forward (on your stomach), but always look ahead, both when descending and when ascending.

If a passer-by walks past the hill, wait until he passes, and only then make the descent.

If it is impossible to get away from a collision (a tree, a person, etc.) on the way, then you should try to fall on your side on the snow or roll away from the ice surface.

Avoid skiing hills with uneven ice.

In case of injury, immediately provide first aid to the victim, report this to the emergency call service 01.

At the first sign of frostbite, or if you feel unwell, stop riding immediately.

There are a huge number of different slides now available, so you can find the right one to enjoy riding on any slide: from steep icy to gently sloping, covered with fresh snow.

Convenient means of transportation on the ice slide:

Ledyanka plastic. The simplest and cheapest device for skiing in winter. They are intended for single skiing on icy and rolled snow slopes. The ice rinks are designed for children from 3 years old, because. It's hard for kids to manage. The plate-shaped ice cube becomes uncontrollable if you sit in it with your feet.

ice trough it is very unstable, at the slightest unevenness it strives to fall on its side - thus, having flown up on a springboard, you can land upside down. Ledyanki are not designed for springboards or any other obstacles, because. any sharp jump on the hill is fraught with unpleasant consequences for the coccyx and spine of the rider!

Ordinary"Soviet" sled great for any snowy slopes. You can steer and brake with your feet. Falling sideways to avoid a dangerous collision is also quite easy and safe.

Snow scooter. For family skiing, you should not choose a snow scooter - it is designed for one or two kids aged 5 to 10 years. More than once, cases were noticed when snow scooters clung to an obstacle (tree root, snow mound) with the front skid and turned over. It is difficult to get off a snow scooter at high speed, and speed is vehicle develops considerable on any slope and accelerates quickly. The brakes are located at the front, which increases the risk of rolling over your head when trying to brake hard. If an adult rides from a high mountain with a child, putting the baby on a snow scooter in front, it will be very difficult for them to steer, brake and evacuate in case of danger.

Cheesecakes. AT recent times inflatable sleds are increasingly found on our slides. The most common inflatable circles are “sled-cheesecakes”. The cheesecake is light and rides well even in fresh snow on a completely unrolled hill. It is best to ride cheesecakes from gentle snowy slopes without obstacles in the form of trees or other people. As soon as the movement speed increases, the cheesecake becomes quite dangerous. Cheesecakes accelerate with lightning speed, and the speed is higher than a sled or a snow scooter on a similar slope, and it is impossible to jump off the cheesecake at speed. You can’t ride on cheesecakes from slides with springboards - when landing, the cheesecake is very springy. Even if you do not fly off, you can get severe back injuries and cervical spine. A good version of the “cheesecake” is a small inflatable ice rink (about 50 cm in diameter) - it’s easy to fall on your side (get off).

Carefully consider the choice of slides and means for skiing!

The hill is a place of increased danger, and not just another entertainment on winter walk along with building snowmen and feeding birds! When riding children with adults, it is important not to forget that speed depends on mass. That is, the steeper and "icier" the hill or the larger the mass ("dad is big and strong, it's not scary with him"), the more deadly the force of the collision. That is why even in cars children are required to be carried fastened in car seats, and not in the hands of adults and not fastened together with an adult with one belt. The force of friction is not Magic power She won't let you stop instantly!

Conclusion

We found out that a person has long been using knowledge about the phenomenon of friction, obtained empirically.

Now we know exactly when the friction force occurs.

We have created a series of experiments to help understand and explain some of the "difficult" phenomena of nature.

We have defined literary works, which refers to the force of friction.

Most importantly, we realized how great it is to get knowledge ourselves, and then share it with others.

List of used literature

1. Elementary textbook of physics: Study guide. At 3 pm / Under the editorship of G.S. Landsberg. T.1 Mechanics. Molecular physics. M.: Nauka, 1985.

2. Ivanov A.S., Prokaza A.T. World of mechanics and technology: Book for students. - M.: Enlightenment, 1993.

3. Encyclopedia for children. Volume 16. Physics Part 1 Biography of physics. Journey into the depths of matter. Mechanical picture of the world / Chapter. Ed. V.A.Volodin. - M.: Avanta +, 2010

4. Children's encyclopedia. I know the world: Physics / comp. A.A. Leonovich, ed. O.G. Hinn. - M .: LLC "Firm" AST Publishing House ". 2010.-480s.

http://demo.home.nov.ru/favorite.htm

http://gannalv.narod.ru/tr/

http://ru.wikipedia.org/wiki/%D0%A2%D1%80%D0%B5%D0%BD%D0%B8%D0%B5

http://class-fizika.narod.ru/7_tren.htm

http://www.physel.ru/component/option,com_frontpage/Itemid,1/

http://62.mchs.gov.ru/document/1968180

Physics lesson "The force of friction"

Lesson topic: Friction force.

Lesson Objectives: to update and deepen students' knowledge of the force of friction, to identify the main features of the force of friction, accounting and application in technology.

Equipment: a wooden block, a dynamometer, a set of weights, sheets of sandpaper, felt, a wooden plate, tables, a disk drive, a projector, lesson presentations.

During the classes

I. Motivation.

We know that physics is the science of nature. Recall F.I. Tyutchev:

“Not what you think, nature:

Not a cast, not a faceless face, -

It has a soul, it has freedom.

It has love, it has language."

Yes, nature has its own language, and we must understand it.

The fall of an apple, the explosion of a supernova, the jump of a grasshopper, or the radioactive decay of substances occur as a result of interactions. There are four types of fundamental interactions.

Gravitational interaction

Electromagnetic interaction

Weak interaction

Strong interaction

The quantitative measure of interaction is force. Among the numerous forces of electromagnetic nature, we single out the force of friction. In terrestrial conditions, friction accompanies any movement and rest of bodies.

II. New material.

- Guys, the topic of our lesson is "The force of friction."

We have been familiar with the phenomenon of friction for a long time. On a hike you can hear: "Do not rub your feet", at school - "Erase the notes from the board." The first studies of friction were carried out by the great Italian scientist Leonardo da Vinci more than 400 years ago, but these works were not published. The laws of friction were described by the French scientist Guillaume Amonton in 1699 and Charles Coulomb in 1785.

- Guys, please give the definition of friction force.

- Friction force - a force that interacts when the surfaces of bodies come into contact, preventing their relative movement, directed along the contact surface.

Find out the causes of friction.

“Now, using the proposed equipment, we will determine the friction force. You have dynamometers on your tables. Let's take a bar, attach it to a dynamometer, and we will pull the bar along horizontal surface so that it moves evenly. This force is equal in modulus to the friction force acting on the bar.

I row tree - on a tree
II row tree - felt
III row wood - sandpaper

Why are there different values?

The cause of friction is the roughness of the contacting surfaces: from lubrication, body weight, the state of rubbing surfaces.

Another reason is the intermolecular attraction acting at the points of contact of rubbing bodies. (It appears in those cases when the surfaces of the contacting bodies are well polished).

When solids come into contact, three types of friction are possible.

Experience number 1. Bar, dynamometer (static friction)

We attach the dynamometer to the bar and pull. The acting force between the bar and the surface is the static friction force.

Experience number 2. Bar, dynamometer (sliding friction)

The bar slides over the surface - the resulting friction force is the sliding friction force.

Experience number 3. Trolley, dynamometer

The cart rolls on the surface. The dynamometer shows the force of rolling friction.

Rolling friction is less than sliding and rest friction. However, one of the most ingenious inventions of mankind is the wheel. It is well known that it is incomparably easier to carry a load on a cart than to drag it.

Now let's look at the presentation for this part of the lesson.

Obviously in real life important to consider friction. Let's see how this is done in the problem of the movement of vehicles on the road.

Guys, you see that it takes a certain amount of time for a car to stop completely. Therefore, follow the rules of pedestrians when crossing the road.

In nature and technology, friction has great importance. It can be helpful and harmful. When it is useful, they try to increase it. For example, car tire surfaces are made with ribbed protrusions in winter, when the road is slippery, it is sprinkled with sand.

Friction plays an important role in the life of plants and animals.

Student presentation.

On the role of friction in the life of plants and animals.

In the life of many plants, friction plays a positive role. Plants, due to friction, cling to nearby supports, hold on to them and reach for the light. Friction here is created due to the fact that the stems repeatedly wrap around the supports and therefore fit very tightly to them.

But plants that have root crops, such as carrots, beets, rutabaga. The force of friction on the ground helps to keep the root crop in the soil. With the growth of the root crop, the pressure surrounding land increases, which means that the friction force also increases. That is why it is so difficult to pull large beets, radishes, turnips out of the ground.

For plants such as burdock, friction helps to spread the seeds, which have spines with small hooks at the ends.

These spines are hooked on the fur of animals and move along with them. Seeds of peas, nuts, due to their spherical shape and low rolling friction, move easily on their own.

Through a long evolution, the organisms of many living beings have adapted to friction, have learned to reduce or increase it. So, the body of fish has a streamlined shape and is covered with mucus, which allows them to develop high speed when swimming. The bones of animals and humans in the places of their movable articulation have a very smooth surface, and inner shell The joint cavity secretes a special synovial fluid, which serves as a kind of articular "lubricant". When swallowing food and its movement through the esophagus, friction is reduced due to the preliminary crushing and chewing of food, as well as wetting it with saliva.

The action of the grasping organs (they include the claws of cancer, the forelimbs and tail of some breeds of monkeys, etc.) is also closely related to friction. After all, an object or creature will be the stronger grasped, the greater the friction between it and the grasping organ. The magnitude of the friction force is directly dependent on the pressing force. Therefore, the grasping organs are designed in such a way that they can either cover the prey from two sides and pinch it, or wrap it around several times and, due to this, pull it together with great force.

In all of these examples, friction is beneficial. But it can be harmful, then it must be reduced. In this case, grease or bearings are used.

It would seem that there could be something in common between a bearing and a monument to Peter the Great in St. Petersburg. Let's listen to the historical background.

Student presentation.

Maybe not everyone knows some of the technical details of creating a monument to the great organizer of the Russian state.

For the pedestal of the monument, a monolithic granite block weighing 80 thousand pounds was prepared, i.e. over a thousand tons! And they brought her from the village of Lahti, on the shores of the Gulf of Finland, to St. Petersburg. How, in the 18th century, without powerful tractors or cranes, could people perform such a miracle?

This block was discovered by a local peasant Vishnyakov. The block was called the Thunder-stone, as lightning once struck it, repulsing a large fragment. About 9 km the Thunder-stone traveled by land, and then along the Neva on rafts it was delivered to St. Petersburg. The unprecedented success of Russian technology of that time was even marked by a special medal, on which the inscription was minted: "It is like daring, 1770." Indeed, it was an act of daring! All of Europe was only talking about this unprecedented operation, which had not been repeated since the time of transportation to Ancient Rome Egyptian monuments. How was it done? A bold, witty project for moving the Thunder-stone was given by a blacksmith from state-owned peasants, who, unfortunately, remained unknown. He proposed to roll the stone on specially cast bronze balls enclosed in a sledge. The sledges were large logs with grooves hollowed out along them, upholstered inside with copper. A granite block was placed on a platform of several rows of densely packed logs, under which there were troughs with balls. The peasants driven from the nearest villages with the help of ropes and gates moved the stone to the shore. Several peasants had to constantly grease the balls with beef lard and rearrange them forward after the block had passed through them; For 120 days the Thunder-stone traveled overland like this. Delivered to St. Petersburg and processed by stonemasons, it became an excellent pedestal for the monument to Peter.

Yes, the invention of the Russian peasants served as a prototype of the modern bearing. They are installed in cars, lathes, electric motors and bicycles.

So our lesson has come to an end. Today we talked in detail about one of the forces of the e / m of nature.

Chowdu Arzhaana Baylakovna

Objectives: to find out what role the friction force plays in our life, how a person received knowledge about this phenomenon, what is its nature.

Tasks: trace the historical experience of mankind in the use and application of this phenomenon; find out the nature of the phenomenon of friction, the laws of friction; conduct experiments confirming the regularities and dependences of the friction force; to think over and create demonstration experiments proving the dependence of the friction force on the force of normal pressure, on the properties of contacting surfaces, on the speed of the relative motion of bodies.

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Friction Force Project

Objectives: to find out what role the friction force plays in our life, how a person received knowledge about this phenomenon, what is its nature.

Report of a group of public opinion researchers.

Objectives: to show what role the phenomenon of friction or its absence plays in our life; answer the question: “What do we know about this phenomenon?”.

Proverbs and sayings:

There will be no snow, there will be no trace.

A quiet cart will be on the mountain.

Difficult to swim against the water.

You love to ride, love to carry sleds.

Patience and work will grind everything.

From that, the cart sang that it had not eaten tar for a long time.

And he scribbles, and rolls, and strokes, and rolls, and all with his tongue.

He lies that he sews with silk.

Fairy tales:

- "Kolobok" - rolling friction.

(“Kolobok lay down, took it and rolled - from the window to the bench, from the bench to the floor, along the floor to the door, jumped over the threshold, and into the canopy and rolled ... ..”)

- "Kurochka Ryaba" - rolling friction.

(“The mouse ran, wagged its tail, the testicle rolled, fell and broke.”)

- "turnip" - friction of rest.

- "Bear Hill" - sliding friction.

Friction is a phenomenon that has accompanied us since childhood, literally at every step, and therefore has become so familiar and invisible.

Take a coin and rub it on a rough surface. We will clearly feel the resistance - this is the force of friction. If you rub faster, the coin and notebooks will fall off the table, the table will slide until it hits a corner, and the pen slips out of your fingers.

Friction contributes to stability. The carpenters level the floor so that the tables and chairs stay where they are.

However, small friction on ice can be successfully used technically. Evidence of this is the so-called ice roads, which were arranged for the removal of timber from the felling site to the railway or to rafting points. On such a road, which has smooth ice rails, two horses pull a sleigh loaded with 70 tons of logs.

Friction is not only a brake on movement. This is also the main reason for the wear and tear of technical devices, a problem that man also faced at the very dawn of civilization. During excavations of one of the most ancient Sumerian cities - Uruk - the remains of massive wooden wheels, which are 4.5 thousand years old, were found. The wheels are studded with copper nails for the obvious purpose of protecting the wagon train from wear and tear.

And in our era, the fight against wear of technical devices is the most important engineering problem, the successful solution of which would save tens of millions of tons of steel, non-ferrous metals, and drastically reduce the production of many machines and spare parts for them.

Already in antiquity, engineers had at their disposal such important means for reducing friction in the mechanisms themselves as a replaceable metal plain bearing lubricated with grease or olive oil, and even a rolling bearing.

The world's first bearings are belt loops that support the axles of antediluvian Sumerian carts.

Bearings with replaceable metal inserts were well known in Ancient Greece where they were used in well gates and mills.

Of course, friction plays a positive role in our life, but it is also dangerous for us, especially in winter, during the period of ice. Here are the data that we were told in a rural hospital: the number of people who applied for medical help in December-January, only schoolchildren, aged 12-17 years, was 3 people. Mostly diagnoses: fractures, bruises. There are elderly people among those who applied for help.

Here are the data from the traffic police on traffic accidents for the winter period: the number of accidents, including those due to slippery roads - 18.

The group also conducted a small sociological survey of a group of residents who were asked the following questions:

1. What do you know about the phenomenon of friction?

2. How do you feel about ice, slippery sidewalks and roads?

3. Your wishes to the administration of our city.

The majority of respondents could not give a definite answer to the first question, because did not see the connection between friction and everyday experience.

To the second question, children and schoolchildren of the middle classes said that they liked the ice, they could ride: and older people already understand what the danger of this phenomenon is. They made a number of proposals to the administration, for example: to sprinkle roads and sidewalks with sand, to make good lighting so that dangerous places are visible; limit the speed of transport during ice; hold talks in schools about first aid medical care in such cases; hold meetings with traffic police inspectors.

Report of a group of theorists.

Objectives: to study the nature of friction forces; to investigate the factors on which friction depends; consider the types of friction.

Friction force

If we try to move the closet, we will immediately see that it is not so easy to do it. His movement will be hindered by the interaction of the legs with the floor on which he stands. There are 3 types of friction: static friction, sliding friction, rolling friction. We want to find out how these species differ from each other and what do they have in common?

Friction of rest

In order to find out the essence of this phenomenon, you can conduct a simple experiment. Let's put the block on an inclined board. When not too high angle the tilt of the board, the bar can stay in place. What will keep it from sliding down? Friction of rest.

Let's press our hand to the notebook lying on the table and move it. The notebook will move relative to the table but rest in relation to our palm. How did we make this notebook move? With the help of rubbing the rest of the notebook against the hand. The static friction will mix the loads on the moving conveyor belt, prevent the laces from untying, keep the nails driven into the board, etc.

The static friction force can be different. It grows along with the force that strives to move the body from its place. But for any two bodies in contact, it has a certain maximum value, which cannot be greater than. For example, for a wooden block on a wooden board, the maximum static friction force is approximately 0.6 of its weight. By applying a force to the body that exceeds maximum strength rest friction, we will move the body from its place, and it will begin to move. The static friction will then be replaced by sliding friction.

History reference

The year was 1500. The great Italian artist, sculptor and scientist Leonardo da Vinci conducted strange experiments, which surprised his students.

He dragged along the floor either a tightly twisted rope, or the same rope in its entire length. He was interested in the answer to the question: does the force of sliding friction depend on the size of the area of bodies in contact in motion? The mechanics of that time were deeply convinced that the larger the contact area, the greater the friction force. They reasoned something like this: the more such points, the greater the force. It is quite obvious that on a larger surface there will be more such points of contact, so the friction force should depend on the area of the rubbing bodies.

Leonardo da Vinci doubted and began to conduct experiments. And I got a stunning conclusion: the force of sliding friction does not depend on the area of the bodies in contact. Along the way, Leonardo da Vinci studied the dependence of the friction force on the material from which the bodies are made, on the magnitude of the load on these bodies, on the sliding speed and the degree of smoothness or roughness of their surface. He got the following results:

It does not depend on the area.
It does not depend on the material.
It depends on the magnitude of the load (in proportion to it).
It does not depend on the sliding speed.
Depends on surface roughness.

1699 The French scientist Amonton, as a result of his experiments, answered the same five questions in this way. For the first three - the same, for the fourth - it depends. On the fifth, it does not matter. It turned out, and Amonton confirmed such an unexpected conclusion by Leonardo da Vinci about the independence of the friction force from the area of the bodies in contact. But at the same time, he did not agree with him that the force of friction does not depend on the speed of sliding; he believed that the sliding friction force depends on the speed, but he did not agree with the fact that the friction force depends on the surface roughness.

During the eighteenth and nineteenth centuries, there were up to thirty studies on the subject. Their authors agreed on only one thing - the friction force is proportional to the force of normal pressure acting on the bodies in contact. There was no agreement on other issues. The experimental fact continued to bewilder even the most prominent scientists: the friction force does not depend on the area of the rubbing bodies.

1748. Active Member Russian Academy Leonhard Euler published his answers to five questions about friction. The first three are the same as the previous ones, but in the fourth he agreed with Amonton, and in the fifth - with Leonardo da Vinci.

1779. In connection with the introduction of machines and mechanisms into production, there is an urgent need for a deeper study of the laws of friction. The outstanding French physicist Coulomb took up the solution of the problem of friction and devoted two years to this. He set up experiments at a shipyard, in one of the ports of France. There he found those practical production conditions in which the force of friction played an important role. Coulomb answered all questions - yes. The total friction force, to some small extent, still depends on the size of the surface of the rubbing bodies, is directly proportional to the normal pressure force, depends on the material of the contacting bodies, depends on the sliding speed and on the degree of smoothness of the rubbing surfaces. In the future, scientists became interested in the question of the effect of lubrication, and types of friction were identified: liquid, clean, dry and boundary.

Right answers.

The force of friction does not depend on the area of the bodies in contact, but depends on the material of the bodies: the greater the force of normal pressure, the greater the force of friction. Precise measurements and show that the modulus of the sliding friction force depends on the modulus of the relative velocity.

The friction force depends on the quality of the processing of rubbing surfaces and the increase in the friction force as a result. If the surfaces of the bodies in contact are carefully polished, then the number of points of contact with the same force of normal pressure increases, and, consequently, the friction force also increases. Friction is associated with overcoming molecular bonds between contacting bodies.

Friction coefficient

The friction force depends on the force that presses the given body against the surface of another body, i.e. on the force of normal pressure Rd and on the quality of rubbing surfaces.

In an experiment with a tribometer, the force of normal pressure is the weight of the bar. Let us measure the force of normal pressure, equal to the weight of the cup with weights at the moment of uniform sliding of the bar. Let us now double the force of normal pressure by placing weights on the bar. Putting additional weights on the cup, we again make the bar move evenly.

The force of friction will then double. On the basis of such experiments, it was found that, with the material and condition of the rubbing surfaces unchanged, their friction force is directly proportional to the force of normal pressure, i.e.

Ftr=µ Ν

Since in the experiments described all the cups with weights are always less than the weight of the bar, it can be concluded that the friction force is always only a part of the normal pressure force N (or Pd). The coefficient of proportionality µ in the formula is less than one and must be an abstract number. It is constant for the same friction surfaces and changes when they are replaced.

The value characterizing the dependence of the friction force on the material and the quality of processing of rubbing surfaces is called the coefficient of friction. The coefficient of friction is measured by an abstract number showing what part of the force of normal pressure is the force of friction

µ=N/Ftr

µ depends on a number of reasons. Experience shows that the friction between bodies of the same substance, generally speaking, is greater than between bodies of different substances. Thus, the coefficient of friction of steel on steel is greater than the coefficient of steel on copper. This is explained by the presence of molecular interaction forces, which are much greater for homogeneous molecules than for heterogeneous ones.

It affects the friction and the quality of processing of these surfaces differently, then the sizes of the roughnesses on the rubbing surfaces are not the same, the stronger the adhesion of these roughnesses, i.e. more than µ friction. Consequently, the same material and quality of processing of both rubbing surfaces corresponds to the highest value of friction µ. It should be noted that interaction forces play an important role in friction between smoothly polished surfaces. If in the previous formula Ftr meant the force of sliding friction, if Ftr replace highest value static friction force Fmax., then µ will denote the coefficient of static friction

µ = Fmax/Rd

Now let's check whether the friction force depends on the area of contact of the rubbing surfaces. To do this, we put 2 identical bars on the skids of the tribometer and measure the friction force between the skids and the "double" bar. Then we put them on the runners separately, interlocking with each other, and again measure the friction force. It turns out that, despite the increase in the area of rubbing surfaces in the second case, the friction force remains the same. It follows that the friction force does not depend on the size of the rubbing surfaces. Such, at first glance, a strange result of the experiment is explained very simply. By increasing the area of rubbing surfaces, we thereby increased the number of irregularities engaging with each other on the surface of the bodies, but at the same time we reduced the force with which these irregularities are pressed against each other, since we distributed the weight of the bars over a large area.

Experience has shown that the friction force depends on the speed of movement. However, at low speeds, this dependence can be neglected. While the speed of movement is low, the friction force increases with increasing speed. For high speeds, an inverse relationship is observed: with increasing speed, the friction force decreases. It should be noted that all established relationships for the friction force are approximate.

The friction force varies significantly depending on the state of the rubbing surfaces. It decreases especially strongly in the presence of a liquid layer, such as oil, between the rubbing surfaces (lubrication). Lubrication is widely used in engineering to reduce the forces of harmful friction.

The role of the friction force

In technology and in everyday life, friction forces play a huge role. In some cases, friction forces are beneficial, in others they are harmful. Friction forces are held by driven nails, screws, nuts; holds threads in matter, tied knots, etc. In the absence of friction, it would be impossible to sew clothes, assemble a loom, put together a box.

The more a person pushes the Earth back, the greater the static friction force applied to the leg, and the faster the person moves.

When a person pushes the Earth away with a force greater than the ultimate static friction force, the foot slides backwards, making walking difficult. Remember how difficult it is to walk on slippery ice. To make it easier to walk, it is necessary to increase rest friction. For this purpose, the slippery surface is sprinkled with sand. This also applies to the movement of an electric locomotive, a car. The wheels connected to the engine are called driving.

When the driving wheel, with the force generated by the engine, pushes the rail back, then a force equal to the static friction and applied to the wheel axle moves the electric locomotive or car forward. So the friction between the driving wheel and the rail or the ground is useful. If it is small, then the wheel slips, and the electric locomotive and the car stand still. Friction, for example, between the moving parts of a running machine is harmful.

The force of friction is also used to keep bodies at rest or to stop them if they are moving. The rotation of the wheels is stopped with the help of brake pads, which are pressed against the wheel rim in one way or another. Air brakes are the most common, in which the brake pad is pressed against the wheel using compressed air.

EXPERIMENTAL GROUP REPORT

Target: find out the dependence of the sliding friction force on the following factors:

From the load;

From the area of contact of rubbing surfaces;

From rubbing materials (with dry surfaces).

Equipment: laboratory dynamometer with a spring stiffness of 40 N/m; dynamometer

round demonstration (limit - 12ң); wooden bars - 2 pieces; a set of cargoes;

wooden board; a piece of metal sheet; flat cast iron bar; ice; rubber.

Experimental results

Dependence of the sliding friction force on the load.

m (g)			1120
F tr (N)

The dependence of the friction force on the area of contact of the rubbing surfaces.

S (cm)
F tr (N)	0,35	0,35	0,37

The dependence of the friction force on the size of the irregularities of the rubbing surfaces: wood on wood (various methods of surface treatment).

Uneven surface - the bar is unfinished.
Smooth surface - the bar is planed along the grain of the wood.
The polished smooth surface is treated with sandpaper.
In the study of the friction force from the materials of rubbing surfaces, we use one bar with a mass of 120 g and different contact surfaces. we use the formula:

Ftr=µ N

We calculated sliding friction coefficients for the following materials:

No. p / p	Rubbing materials (for dry surfaces)	Coefficient of friction (when moving)
	Wood by wood (average)
	Wood on wood (along the fibers)	0,075
	wood for metal
	wood for cast iron
	tree on ice	0,035

DESIGN GROUP REPORT

Goals: create demonstration experiments; explain the results of the observed phenomena.

Friction experiments

After studying the literature, we selected several experiments that we decided to carry out ourselves. We thought out the experiments, made the instruments, and tried to explain the results of our experiments. As devices and instruments we took: violin, rosin; wooden ruler; a wooden egg through which a thread is passed.

Experience #1

Carefully rub the bow with rosin, then run it along the string. Continuous singing sounds are obtained due to friction. When the violinist begins to lead the bow along the string, the string is also carried away by the bow under the action of the static friction force and bends. In this case, the tension tends to return it to its original position. When this force exceeds the rest force, the string breaks and vibrates, the violinist moves the bow in the opposite direction, and then towards. The violin sings. If you play the violin without a bow, pulling the strings with your fingers, you get a sound like a balalaika; if you pull the string with your finger and release it, you will hear a sharp sound that quickly fades.

Then rub the bow with rosin? Does rosin act as a friction lubricant? It turns out that the bow is rubbed with rosin not only so that this force would noticeably depend on the sliding speed, but would decrease faster with increasing speed. The string under the bow always moves slower than the bow. When the bow and string move in the same direction, the string lags behind the bow. The force of friction prevents settling and drags the string behind the bow. The force of friction does work, the bow drags the string along with it and, conversely, slows down the string, slowing down its movement. Work is done against the forces of friction. It turns out that on one half of the way the bow helps the string, and on the other it hinders it? This does not happen for two reasons. First, the speed with which the bow slides along the string is different relative to the string. When the string and the bow move in the same direction, the speed of the bow is slow. Remember how a passing car moving along the road slowly lags behind, if you look at it from the window of a fast moving train. When the string moves towards the bow, its speed is much greater - like the speed with which an oncoming car flickers through the window. The second circumstance is that the force of sliding friction depends on the relative speed of the rubbing surfaces. With slow sliding, when it moves in the same direction as the string, with fast sliding, the string and bow move in different directions. Thus, for each vibration of the string, the friction force pushes it forward, preventing these vibrations from dying out.

Experience #2

A wooden egg with a thread passed through the middle. They take the ends of this thread in their hands, and raise one hand high up. A wooden egg on a thread quickly slides down. Raise the other hand up. The egg rushes down again, but suddenly gets stuck in the middle of the thread, then slips again and stops. In this experiment, the sliding friction force is proportional to the normal pressure force. The egg consists of two connecting halves. A cork plug is fixed in the center perpendicular to the thread. When the thread is pulled, the friction force of the thread on the cork increases and the egg freezes in a certain position on the thread. If the thread is not tightened, then the friction force is less and the egg slides freely down.

Experience #3

Wooden ruler. Put the ruler horizontally on the index fingers begin to pull together. The ruler does not move evenly across two fingers at once. She slides in turn on one, then on the other finger. Why? Only the finger that is further from the center of mass of the ruler slides under the ruler, since it experiences less load and less friction. Its sliding stops as soon as it is closer to the center of mass of the ruler than the second finger, and then the second finger begins to slide. So the fingers move towards the center of gravity of the ruler alternately.

At the beginning of December, a week of mathematics and physics was held. The authors of the project made a competition of fairy tales among students “Imagine a world without friction.” The best fairy tales obtained from the following students.

Fairy tale 1.

"In the world of friction". (Lakpa Ch)

Sitting in a physics lesson, Ivanov did not listen to the teacher. "And why do you need to know about this friction, no one needs it, and you can do without it," he thought. And suddenly he felt that he had hit something hard, he tried to get up, but fell again. Ivanov nevertheless got up and, barely moving, went. Everything around was somehow strange, smooth, no matter what he touched, everything was smooth. "Strange, and there are no cars?" Ivanov was surprised. "But how will they ride?" came a voice from behind. Ivanov looked around and saw a boy with a crown on his head and some strange devices on his legs.
- How will they ride if there is no friction? said the boy with the crown.
- How is there no friction?
- So after all, you got into the country without friction, and I am the king of this country.
- What's on your feet?
- These are special devices for movement, you need to put them on, otherwise you will not go even three steps.

Ivanov put on these devices and it became easier for him to move around. Looking closely at the king, he saw that the crown was attached to the head with some unusual device.
- Why did you attach the crown?
- You forgot that in our country there is no friction, try to put on a headdress, it will immediately fall off.

And then, Ivanov realized that in vain he said that friction is not needed. He began to look around and a harmonious picture appeared to his eyes: all the people walked on some special devices, it was impossible to climb a tree, since it was very smooth. All objects, at the slightest touch, fell.
- How bad without friction!
- Yes, but even without him, something is going well with us. Planes fly very fast, engines do not wear out, ships swim fast. But it's still bad without friction. You see that in my country there is nothing beautiful and amazing, you can’t draw, run, climb trees, and you are to blame for this!
- I!?
- Yes, you, it was you who said that friction is not needed, so stay here as a king, and I'm leaving!
- But I didn't want to, I didn't want to, I didn't know!
"Ivanov, what is friction?" asked the teacher.

Ivanov woke up, he was sitting at his desk in the physics room: "Friction is a force without which one cannot live." - he answered and he was right!

Fairy tale 2.

"Adventures of Savushkin."(Doktugu A 8th grade)

Once Savushkin received a deuce in physics. They just passed the topic "The force of friction".

Arriving home, throwing his textbook on physics into a far corner, he thought with hatred: "Go to hell, friction force."

And suddenly he slipped and fell out of the blue. Savushkin tried to get up, grabbing the leg of a chair. The chair easily jumped out of his hands and flew off to the side, knocking over a bookcase with books. The room was in turmoil. Objects flew from their places and, circling around the room, collided and scattered in different directions. From the far corner, waving the pages, a physics textbook flew out. The room was like a spaceship in zero gravity. Savushkin, gathering his strength, tried to catch the textbook. Suddenly it dawned on him: at his request, the force of friction disappeared. Savushkin flew around the room and caught up with the textbook. Finally, he grabbed it, opened the given page on the fly and read the paragraph and realized how important the force of friction is in life. Thanks to the force of friction, buses drive through the streets, people and animals walk, skiers glide on the snow, skaters ride on ice, objects stay in place.

Suddenly everything in the room fell into place. The force of friction resumed its action. Savushkin breathed a sigh of relief. From that day on, he began to seriously study physics.

Fairy tale 3.

"In a world without friction."(Choodu A-11 class)

One day my friend went to another city. Here is what he told me: “I arrived in the city and went to look for a hotel. Having found it, I paid for a week in advance and went to my room. As soon as I decided to rest, a nasty buzzing sound was heard. Suddenly the bed moved away from the wall to the middle of the room "The floor left under my feet and I fell. The sound stopped. I got up, straightened my suit and sat on the bed. It would seem that nothing had happened, but the bed was in the middle of the room, and there was an abrasion on my knee. But, what was it "I didn't torture myself with this question and still decided to rest. Suddenly, this sound was heard again. This time I decided not to stay in the room. Barely holding on to the walls, I went out into the corridor. What was there! The paths went from under my feet "The cabinet was moving away from the wall, losing its doors along the way, and falling apart. I barely got out into the street. On my way, everything fell apart and fell. On the street, passers-by made some kind of erratic movements, fell. The bus drove at a frantic speed, the driver's face, distorted with fear, poked out of the cab and closed it. chanted: “I can’t stop the car, the brakes don’t work!” Finally, the sound stopped. My neighbor ran out of the hotel with a box in his hands. "Finally! Finally! The force of friction. I invented it" - so he shouted. He ran up to me and shouted "Look!" He turned on some button and ... But there was no sound. The machine fell apart. Instead, on the pavement lay a pile of cogs, screws and all sorts of details. This is all that's left of her. The machine was no exception and the friction force did not act in it either.

Summarizing:

And now let's sum up and evaluate the friction on merit. Of course, only due to the presence of the force of friction in nature is life possible in the form in which it exists on Earth. But at the same time, friction wears out cars and the soles of our shoes, the engines of cars, airplanes, steam locomotives. They all work against friction (dry and liquid), a huge amount is spent on this various kinds fuel. Friction is beneficial in some conditions and harmful in others. Therefore, it is necessary to skillfully use the forces of friction. When we need friction in everyday life, in production, in technology, in transport, we need to increase it.

When friction interferes, causes the consumption of energy and materials, it is necessary to reduce it. This is how people have been doing since time immemorial. But in order to subjugate friction, you need to know what laws govern it.

a) The greater the pressure between the contacting surfaces, the greater the static friction force.

b) How many times the pressure increases, so many times the static friction increases.

c) The magnitude of the friction force depends on the type of rubbing surfaces.

d) The rolling friction force is less than the sliding friction force.

e) Lubrication reduces friction.

Findings

Based on the results of the project.

We found out that a person has long been using knowledge about the phenomenon of friction, obtained empirically. Starting from the 15th-16th centuries, knowledge about this phenomenon becomes scientific: experiments are carried out to determine the dependence of the friction force on many factors, regularities are found out.

Now we know exactly what the friction force depends on, and what does not affect it. More specifically, the friction force depends on: the load or body mass; from the kind of contacting surfaces; on the speed of the relative motion of bodies; on the size of uneven or rough surfaces. But it does not depend on the area of \u200b\u200bcontact.

Now we can explain all the regularities observed in practice by the structure of matter, by the force of interaction between molecules.

We conducted a series of experiments, did about the same experiments as the scientists, and got about the same results. It turned out that experimentally we confirmed all the statements made by us.

We have created a series of experiments to help understand and explain some of the "difficult" observations.

But, probably, the most important thing is that we realized how great it is to acquire knowledge ourselves, and then share it with others.

Literature

1. Bludov M.I. "Conversations in Physics" -M: Enlightenment 1980

2. Gorelov L.A. "Entertaining experiments in physics" -M: Enlightenment 1985

3. Deryagin B.V. "What is friction" -M: Enlightenment 1986

4. Kabardin O.F. "Optional course in physics" -M: Enlightenment 1977

5. Moshchansky V.N., Savelov E.V. "History of Physics in high school". Enlightenment 1981

6. Tarasov L.V. "Physics in nature" -M: Enlightenment 1988

7. Russians folk tales, proverbs, sayings.

Goals and objectives………………………………………………………………………………1

Report of a group of public opinion researchers…………………………….2

Theoretical group report in…… ……………….………………………………………3

Historical background …….…………………………………………………………….4 The role of the friction force………………….………………………… ……………………….5

Report of a group of experimenters……………..……………………………………..6

Designer group report ………………………………………………………..7

Competition of fairy tales ………………………………………………………………………….8

Conclusion…………………………………………………………………………………9

District competition research work and projects of schoolchildren

"Smart Generation"

Project theme: "The force of friction"

Chowdu Arzhaana, Lakpa Choduraa

MOU OSSH village Ilyinka

10.11 class

Head: Doktugu O.B.

Physics teacher

MOU OSSH s. Ilyinka.

February 2010