Development of a physics lesson on the topic: “Friction force.” Open lesson on physics "friction force" Physics lesson friction friction force

Purpose of the lesson To become familiar with the force of friction; find out whether the force of friction is really stronger than storms, winds and bad weather; experimentally establish the causes of the friction force; find out what types of friction force exist, and also find out the positive and negative role of friction force in human life.

Experiment 1 Observation of the phenomenon of friction There is a wooden block on the table. Push it and watch its movement. Attach a dynamometer to it and pull evenly. Replace the block with a cylinder and do the same. What can you say about the speed of the body? How did it change during the experiments?

Experiments 2 and 3. Finding out the causes of friction. Let us establish 2 causes of friction and the presence or absence of similarities between the friction force and the elastic force. Experiment 2: Take 2 glass plates, press them together, and then move one plate relative to the other. What are you observing? Why are the plates difficult to move? Drop 2-3 drops of water onto one plate with a pipette and repeat the experiment. Why has it become even more difficult to move the plates? Experiment 3: Take 2 pieces of sandpaper and a magnifying glass. Consider the surface of these bodies. Fold them and try to move them relative to each other. Name 2 causes of friction.

Friction force causes what determines the mutual attraction of molecules of contacting surfaces quality of processing of contacting surfaces type of substance lubricant magnitude of the pressing force bearings types of friction force sliding friction force rolling friction force static friction force roughness of contacting surfaces

I offer questions in poetic form: “Well, friends, tell me, Why is it difficult to hold a live fish in your hand? Well, who, guys, knows: Why do they sprinkle sand on our roads in winter? Skating with sand, Egorka somehow climbed up the hill. Well, now figure it out: Will Egorka slide down?

Our attitude towards friction is very contradictory. On the one hand, a merciless battle is being waged against friction: the rubbing surfaces of machines are carefully ground, simple plain bearings are replaced with ball or roller bearings, abundant lubrication is used, and much work is being done to create new ideal lubricants. On the other hand, what would we do if friction suddenly disappeared? Even when walking, friction is of great service to us - it is so difficult to walk on slippery ice. Cars and trains would not be able to move without friction. And if some body moves, slides, in order to stop it, you need to make an effort.

Should we get rid of friction? In the absence of friction, nails and screws would slip out of the walls, not a single thing would be able to be held in the hands, no whirlwind would ever stop, no sound would cease, but would echo endlessly, incessantly reflecting, for example, from the walls of a room. An object lesson that convinces us of the enormous importance of friction is given to us every time by black ice. Caught by her on the street, we find ourselves helpless. Every nation encapsulates its wisdom and life experience in sayings. For example: if you don’t grease, you won’t go; things went like clockwork; You can’t hold an eel in your hands; what is round rolls easily; skis glide through the weather; You cannot weave a net from waxed thread; the well rope grinds the frame;

CONCLUSIONS: The friction force is the force that arises when one body moves along the surface of another. Types of friction forces: static friction force, sliding friction force, rolling friction force. The reasons for the appearance of friction force: - intermolecular interaction of the surfaces of contacting bodies; - roughness of contacting surfaces Friction force: - directed in the direction opposite to the movement; - has a point of application - a set of points of contact between the surfaces of interacting bodies; - weakly depends on the speed of relative motion of interacting bodies; -DEPENDS on the type of rubbing surfaces, i.e. on the material and on the quality of surface treatment of interacting bodies; - depends on the strength of normal pressure and increases with its increase; - DOES NOT DEPEND (to a significant extent) on the area of the rubbing surfaces.

Thank you for your good work. And perhaps in the distant future one of you will become a great scientist, and we will all be proud of it. For, as the great M.V. Lomonosov wrote, the Russian land can give birth to its own Platos And quick-witted Newtons! Thank you, children, for the lesson!

Educational:

deepen students’ understanding of the force of friction, reveal its nature, show what types of friction there are;
using an experiment, establish what the friction force depends on, establish a mathematical relationship between the friction force and the support reaction force;
instill a culture of physical speech, the ability to build a graph based on experimental data, the ability to work with a device (dynamometer), take readings from the device, analyze and compare.

Educational:

development of speech, logical thinking, ability to work, the ability to apply acquired knowledge in a non-standard situation, creative abilities, interest in the history of physics.

Educational:

ability to work in a group;
the ability to achieve a goal using the example of biographies of scientists.

Method: problematic, research, reproductive.

Interdisciplinary connections: mathematics, literature, physics 7th grade.

Equipment: wooden block, wooden ruler, dynamometer, set of weights, glass, rubber.

Office decoration.

Statements and brief biography of scientists at the stand. Annex 1.

“Knowledge not born from experience, the mother of all reliability, is fruitless and full of errors.”

Leonardo da Vinci

During the classes

1. Statement of the problem

“When I was a schoolboy, my friends and I stole three bars of soap from the house and rubbed them on the rails as they went up. That job took us three hours. But we hid in the bushes and watched as the loaded train tried to climb the hill for half an hour, but kept sliding down. I returned home a happy person, with a feeling of a job well done. But my father was already waiting for me at home with a belt, I didn’t have time to ask what I would get for it. My friends were luckier; their fathers did not work on the railroad, unlike my father. So I understood what it was coefficient of sliding friction".

(From Honored Teacher of Russia V.I. Tkachuk)

Question: “What did the student understand, and what exactly was discussed in the memory?”

There is a discussion and conclusion: about the action of the friction force.

Teacher: “The topic of our lesson is “Friction Force.”

2. Historical background.

Leonardo da Vinci (06/15/1452 – 05/02/1519) - Italian artist, scientist and inventor.

Amonton Guillaume (08/31/1663 – 10/11/1705) - French physicist, Member of the Paris Committee of People (1699).

Pendant Charles Augustin (06/14/1736 – 08/23/1896) - French physicist and military engineer, member of the Paris Academy of Sciences (1803).

3. Frontal conversation.

400 years ago, friction was discovered - the toughest nut to crack in natural science. Friction occurs literally at every step, without it you can’t even take a step; We hold a pen, in our hand - friction, we write this very phrase - friction; all sorts of objects stand on the table and do not slide off - friction; nails hold a shelf with books, do not come out of the wall - friction, etc. and so on.

When does friction occur? Where is the friction force directed? (When the surfaces of bodies come into contact. The friction force is always directed in the direction opposite to the speed).

There is some mechanism for the interaction of surfaces. Usually they talk about small notches on the surface of bodies that cling to each other. The following fact leads to this idea: when cleaning surfaces, friction decreases - this is what floats. In fact, the mechanism of interaction between contacting surfaces is much more complex and needs to be analyzed at the molecular level. Since the friction force is of an electromagnetic nature.

4. Friction. Brief summary.(Make an explanatory drawing. Write a definition. Cause of occurrence)

Static friction force.
Rolling friction force.
Sliding friction force.

Formula for calculating friction force: F = µN, where N = mg

About the force of friction

There is a force of friction in the world.
It makes a big difference!
There are three types of friction: sliding, resting, rolling.
All of them are very important
And in this world, of course, they are needed. (V. Sayapin)

5. Physical experiment.

Students complete assignments in groups and write a report. The strongest students do tasks 1 and 2, others - 3 and 4.

Experimental work. “Friction force measurement”

If you place a block on a horizontal surface and apply sufficient force to it in the horizontal direction, the block will begin to move. In order for the block to move uniformly and in a straight line, the modulus of the traction force must be equal to the modulus of the friction force.

The method for measuring friction force is based on this.

Instruments and materials: a tribometer consisting of a wooden block with three holes and a wooden ruler, a school dynamometer, a set of weights on mechanics.

Exercise 1. Determine the dependence of friction force on body weight.

Determine the mass of the block and the weight from the set.
Having hooked the hook of the dynamometer to the hook of the block, set them in uniform motion along a ruler (or table surface), measure the traction force.
Loading the block with one, two or three weights, measure the friction force in each case. Enter the data into the table.

Test body	Mass m, g	Gravity F, N	Friction force F, N	Friction coefficient
Bar with one weight
Bar with two weights
Block with three weights

Task 2. Determine the friction coefficient

Using the experimental points, construct a graph of the dependence of the friction force on the force __________________________. This dependence is _________________. Since the scatter of experimental points is inevitable, the graph of the dependence of force F on force _______________________ (a straight line passing through the origin of coordinates) must be constructed so that it passes as close as possible to all experimental points.

Graph F(N). µ = F/N

Task 3. Determine the dependence of friction force on surface area

1.Measure the length, width and height of the block and calculate the area of the base of the block and the side surface.

a = _______cm	b =________cm	c =_________cm
S =___________cm 2		S =______________cm 2

2. Place the block with its side edge on the ruler and measure the friction force F =____N

3. Place the block with its base on the ruler and measure the friction force F =____N

Conclusion:__________________________________________________________

Task 4. Determine the dependence of the friction force on the surface on which the body moves.

The dynamometer reading when the block moves on wood is __________N.

Indication of the dynamometer when the block moves on a rough surface___________N.

Indication of the dynamometer when the block moves on the glass _____________Н.

The dynamometer reading when the block moves on the rubber is _____________N.

Draw a conclusion _________________________________________________

________________________________________________________________
________________________________________________________________

CONCLUSION: (what did you learn about the force of friction):___________________________.

6. Discussion of the results of the assignments.

Conclusion: the friction force depends on the surface of movement, on the reaction force of the support and does not depend on the surface area.

7. Qualitative tasks.

What is easier: to move the body or continue to move it along a horizontal surface?
Why?
Why are the paths sprinkled with sand in winter?
Why do they put chains on the rear wheels of cars in winter?
Why do they put tread on shoes and car tires?
Why is oil poured into a car engine?
Why do ski athletes apply a special lubricant to their skis?
Why are the bearings of bicycle wheels and pedals lubricated with grease?
How does an all-terrain hovercraft work? What is its lubricant?
The sword is a bony extension of the fish's upper jaw. It easily cuts through the water and significantly improves the hydrodynamic characteristics of the fish.
Here is a swordfish that sets records for speed of movement under water - 130 km/h. But what would the sword be worth if it weren’t for the protein lubricant mucin, which negates the friction of the fish on the water.
How does friction with water occur? How do fish reduce resistance?
Give a physical basis for the proverb: “Mow while there is dew; the dew is gone and we’re home.” Why is it easier to mow when there is dew?
- Explain the sayings:
- If you don’t butter it up, you won’t go!
- Things went like clockwork.
- You can't hold an eel in your hands!
- Skis glide according to the weather.
- You can't make a net out of waxed thread.
A rusty plow is cleaned only after plowing.
Petya examined the nail. The cap had a notch in the form of a mesh, and under it, on the top of the shaft, there were several transverse scratches. “What is this for?” he asked his dad, who was building a barn.
It's starting to get dark. Robinson thought: “It would be nice to light a fire.” But then I remembered: “There are no matches.” What to do? How to light a fire without matches?
The area around the school was undergoing renovations. The worker put the ladder against the pole and tried to climb it, but the ladder was unsteady, since the top step, resting on the pole, was sliding off it. Vovochka, passing by, saw this scene and advised: To prevent the ladder from slipping, replace the top step with a strong rope or a piece of rope. I’ve already done this: everything is fine.”

Is there a scientific basis for this advice?

8. Summing up the lesson and homework.

Prepare reports on the topics “Friction in living nature”, “Friction in everyday life and technology”.

An essay on the topic “What would happen if there were no friction force.”

9. Presentations on the force of friction.

Literature.
Elkin V.I. “Unusual educational materials in physics.” “Physics at school” magazine library, No. 16, 2000.
Wisdom of millennia. Encyclopedia. Moscow, Olma - press, 2006.
Non-standard crocs. Physics grades 7-11.
Publishing house Uchitel”, Volgograd, 2004.
Semke A.I. Physics lessons in 9th grade. Yaroslavl, Academy of Development, Academy Holding, 2004.

Physics and Astronomy, textbook for grade 7, edited by A.A. Pinsky, V.G. Razumovsky, Moscow “Enlightenment” 2002.

Khramov Yu.A.. Physicists. Biographical reference book.

Moscow “Science”, 1983. consolidate acquired knowledge about forces in nature; introduce students to the force of friction; experimentally find out what the friction force depends on; consider the types of “dry” friction; compare rolling, sliding, and static friction; teach students to identify the type of friction; enter the calculation formula for finding the friction force (slide 2).

Necessary technical equipment: interactive whiteboard, computer, projector.

Software: PowerPoint, video player, presentation.

Design: The topic of the lesson and tasks for updating knowledge are presented on the board. Sayings about the force of friction are written (or printed) on the folding halves.

Equipment: a wooden block with edges of different areas, but the same surface roughness; set of weights of 100 g; wooden, poorly polished board; dynamometer, rollers (2 cylindrical objects, for example 2 pencils).

Explanatory note on the use of the presentation. (Annex 1)

During the classes

1. Organizational moment. Hello. Today in class we will try to find out the meaning of some Russian sayings from the point of view of physics. (Slide 3). To do this, we will use experiments to confirm or refute the possibility of the events described. But first, let's remember what we learned in previous lessons and what we will need today.

2. Updating knowledge.

A) One student works at the interactive whiteboard: Depict body weight, elastic force and gravity. (The teacher pays attention to the point of application and direction of the force).(Slides 4, 5)

B) The teacher prepares assignments at the blackboard in advance. While the student is working at the interactive whiteboard, the whole class is working independently in notebooks, the answers will be discussed when checking using a presentation.(Slide 6)

1. Where is the force of gravity greater? Where is the most weight?

2. Where is the elastic force greater (k 1 =k 2)? What can be said about the force of gravity if the bars are at rest? (Slide 7)

3. Where is the stiffness greater (m 1 =m 2)? What can be said about the force of gravity if the bars are at rest? (Slide 8)

4. Determine and designate the resultant of forces. Where will the body move in this case? And if you get rid of the force indicated in black, how will the body move? (Slide 9)

C) Two students (sitting at the same desk) are given a task and equipment: “Construct a graph of body weight versus mass. Equipment: dynamometer, set of weights” Students present the results of their work to the class and draw a conclusion after discussing all the issues.

The teacher observes how students do their work and provides the necessary assistance. After 5-7 minutes a check is organized. Emphasis is placed on the key points that students should have noted when completing assignments.

3. New material

In previous lessons, we have repeatedly touched upon the issue that if no other bodies act on the body or the action of these bodies is compensated, the body is either at rest or moving straight and uniformly (slide 10). A physical quantity that characterizes the action of bodies on each other is called force. Let's conduct an experiment: use a dynamometer to pull a block with weights so that the movement is uniform. Why is this possible? Correct, the traction force in this case is compensated by some other force that is not yet known to us? (Slide 11). Let's try to find out what kind of force this is, where it arises, where it is directed and what it depends on.

The teacher and assistants provide equipment (see above) to each desk.

Conduct the same experiment yourself and think: where is the force unknown to us directed?

This force is called friction force. It is designated Ftr, measured in N. Why does it arise? In connection with the contact of the block and the desk, it means that it arises at the point of contact of two bodies. There are two reasons for the occurrence of friction force (slide 12). When one body slides over the surface of another, the bumps cling to each other, which creates some force that retards the movement. But if you take 2 well-polished objects, for example two glasses, then the friction force also turns out to be great, since in this case mutual attractive forces arise between the molecules of the contacting bodies, which are the cause of friction.

What do you think this power may depend on? Check your guesses. Possible assumptions. (Slide 13, 14)

(It is better to organize work in groups - each group tests one hypothesis and voices and comments on the result)

1. On speed (does not depend).

2. From the transported mass.

The more P, the more Ftr.

4. From surface roughness, etc.

The teacher helps to simulate the students' experiment in such a way as to test all the assumptions made. After this, all findings are recorded.

In notebooks we write down Ftr. (Slide 15)

Directed in the direction opposite to movement.
Occurs at the point of contact of two bodies
Depends: on the weight (mass) of the body and surface roughness.

That. Ftr is calculated by the formula (slide 16): Ftr = µN, where µ is the friction coefficient, depending on the type of rubbing surfaces, N is the support reaction force, i.e. elastic force arising in the support under the influence of body weight.

We give a definition of Ftr - this is the force that arises when the surface of one body interacts with the surface of another, when the bodies are stationary or moving relative to each other.

Now place rollers under the block with weights and measure the friction force. Compare it with the readings you performed for the same weight in the previous experiment. What conclusion can be drawn? That's right, this frictional force is less. Now place the block with weights on a rough surface and try to move it. What is being observed? The force initially increases greatly, and when the block begins to move, it becomes equal to the frictional force obtained during sliding. Those. In nature, three types of “dry” friction are distinguished: sliding friction force, rolling friction force and static friction force.

Place signs between F.rolling tr._____F.sliding tr._____F.rest. (Slide 17)

4. Consolidation

(Slide 18) Arrange the type of friction force for each situation depicted. Give your own examples of each type of friction force.

How can you increase and decrease the friction force?

Explain the meaning of the sayings presented on the board. Do they have physical meaning? (Slide 19)

Additionally: Give examples of the manifestation of the friction force.

Is there any benefit to friction? What?

What harm does friction force cause? Is it possible to fight this? How?

Homework: §30, 31, tasks 1 and 2, home experiment, get acquainted with additional material. (Appendix 2) . ( Issued either in printed or electronic form). (Slide 20).

Bibliography

1. Peryshkin A.V. Physics. 7th grade: textbook. For general education Institutions/A.V. Peryshkin. – 12th ed., - M.: Bustard, 2008.

2. Volkov V.A., Polyansky S.E. Lesson developments in physics: 7th grade. - 2nd edition. – M.: VAKO, 2009.

, experimental activities, friction, types of friction, reasons for friction

Presentation for the lesson

Physics and Astronomy, textbook for grade 7, edited by A.A. Pinsky, V.G. Razumovsky, Moscow “Enlightenment” 2002.

Khramov Yu.A.. Physicists. Biographical reference book.

Lesson Objectives:

Educational:

Students should know the concept of friction force
know types of friction
be able to experimentally establish what the friction force depends on
Students should be able to establish the causes of friction

Developmental:

development of logical thinking
development of experimentation skills
Formation of skills to use devices
Formation of skills to draw conclusions, analyze and compare experimental results

Educational:

involve students in active independent activities
fostering a culture of communication

Teacher Equipment: Computer, multimedia projector, presentation, wooden block, dynamometer, set of weights (3), 2 round pencils, 2 glass slides.

Equipment for students: Dynamometer, sheet of smooth paper, wooden block, set of weights (3), 2 round pencils, 2 glass slides.

Preparation for the lesson: Each table is provided with equipment, information sheets, and a self-assessment sheet.

Plan

Organizational moment (2 min.)
Updating knowledge (2 min.)
Motivational beginning of the lesson (1 min.)
Learning new material (20 min.)
Consolidation of what has been learned. Solving qualitative problems (5 min.)
Running the test (4 min.)
Summarizing. House. exercise. Reflection (5 min.)

During the classes

I. Organizational moment

Teacher: Hello guys! Sit down. (slide 1)

Today's lesson is a little unusual for 2 reasons. I will lead it. My name is Lyudmila Ivanovna, and the second reason is that there are guests at the lesson. But the rest of the lesson is as always - A lesson in gaining knowledge.

So let's start our lesson,
May it benefit you all.
We will listen, answer,
Problems need to be solved.
How, why and why,
And you evaluate it!

In the “Interaction of Bodies” section, you studied the various forces that help us in life. In this lesson we will study another force, no less important, but first, remember what you already know about forces.

II. Updating knowledge

Continue the sentence:

Strength is...
Types of forces:
Unit of force...
Force is measured by a device...
Force is a vector quantity. What does it mean?
The elastic force arises...

III. Motivational start of the lesson

Teacher: Guys, have you ever wondered, “Why does chalk leave a mark on the board?”, “What role does saliva play when swallowing food?”, “Why are needles carefully polished?”

We can answer these questions by studying the lesson material.

But you probably know the answer to the next question: “What physical phenomenon helps you use an eraser to remove an unwanted drawing made with a pencil in a notebook?” (Friction)

Teacher: Right. And to do this, you apply a force to the eraser - the force of friction.

So guys, the topic of the lesson FRICTION FORCE.

Today we will be working on the following lesson map. Opposite the word SUBJECT write down the topic of the lesson.

Based on the topic of the lesson, what questions would you like answered today:

Students:

What is friction force
Types of friction force
Where is it headed?
Where is it used?

Today I will help you find out what friction force is, introduce you to the types of friction force, we will establish the reasons for the occurrence of friction force and experimentally see what the friction force depends on. We will also develop logical thinking, learn to draw conclusions, analyze, compare the results of experience, and see for yourself in practice which type of force is greater.

IV. Learning new material

Teacher: You have been familiar with the phenomenon of friction since childhood. On a hike we say: “Not on rub legs". At school: “So rub from the writing board”, etc.

First experience:

Teacher: You have a wooden block on your table. Take it, place it in front of you and push. What happened to him?

Teacher: The body stopped .

Teacher: Why, what is slowing him down?

Student:- Friction. The surfaces rub against each other, and the body slows down.

Teacher: A frictional force acts on the body.

Teacher: And how is it directed?

Student: Against traffic.

So: The force that arises when one body moves along the surface of another, applied to the moving body and directed against the movement, is called the friction force.

Teacher: Let's go back to the card. Read the definition and try to remember it.

(Ask two or three people). Complete task 1.

Teacher: What did you learn?

After completing the following task, we will learn the causes of friction.

Experience two:

Take a piece of paper and a pencil. Draw any line on the piece of paper with a pencil. Now, try to do the same on glass. What are you observing?

CONCLUSION Student: There was a pencil mark on the paper, but not on the glass.

Teacher: What's the matter?

Consider the surfaces of stylus, paper and glass.

The surface of the paper is rough, just like the lead. And the glass is smooth. When the pencil moves over the paper, parts of the pencil break off on the paper's nervousness, and they remain on the paper. There are no such irregularities on glass.

Teacher: So, what is the cause of friction?

Student: In the roughness of the surfaces of contacting bodies.

Write in the second column next to the number 1

Teacher: Doing experiment 2

Experience three: Press the two pieces of glass harder against each other and try to move one relative to the other.

Student: It's not that easy to do.

Teacher: So what's the deal? After all, there are no rough edges, but still something gets in the way?

Student: Attraction of molecules of interacting bodies.

Write in the second column next to the number 2

Conclusion: causes of friction

Roughness of the surfaces of contacting bodies.
Attraction of molecules of interacting bodies.

Guys, there are three types of friction: sliding friction, rolling friction, static friction

Take your textbook, put a pencil on it, if it starts to slide, then a sliding friction force arises, if it rolls, then a rolling friction force arises.

What do you think, when can the static friction force arise?

Which of these forces do you think is greater?

Let's check this out.

Place the block, attach the dynamometer, and load it with weights. And now attention: Try to move the block by applying force to the dynamometer, and take the maximum value at which the block has not yet begun to move and at the moment when it is already sliding along the table surface. Compare the values on the card.

Place two round pencils under the block and take a reading from the dynamometer. Compare

Static friction.

As they say, every cloud has a silver lining. Friction not only harms movement, it also contributes to the stability of bodies. Without it, everything will roll and slide until it is on the same level. Nails and screws will slip out of the walls, fabrics will unravel, not a single button will be sewn on, the threads simply will not hold in either the needles or the fabrics. Little of. Without static friction we would not be able to walk or drive. Remember how difficult it is to move in icy conditions.

(Perelman Ya.I. Entertaining physics. If there were no friction. p. 263)

Teacher: One of the London newspapers at the beginning of the 20th century wrote: (December 1927)

“Due to severe ice conditions, street and tram traffic in London is noticeably difficult. About 1,400 people were admitted to hospitals with broken arms and legs...”

Teacher: What needs to be done to prevent this from happening again? How can you increase friction?

Student: Sprinkle with sand, therefore, increase surface roughness

Teacher: And they also say that The friction force also depends on the weight of the load.

Test this out.

1. Frontal experience

A) Place one weight on the block and pull it evenly across the table surface. Note and record the dynamometer readings in the table next to one load.
B) Add another weight to the block. Record the readings in the table.
C) Add a third weight to the block. Record the dynamometer readings.
D) Compare the measurement results obtained and draw a conclusion.

Conclusion: The greater the weight, the greater the friction force.

Compare your findings with the table entry.

Teacher: What are some ways to reduce friction?

Student:- Remove irregularities, i.e. sand surfaces

Teacher: Wear of machine parts and mechanisms occurs due to friction. To reduce friction of contacting surfaces, introduce between them lubricant

(slide 10) Ways to reduce friction

Grinding
Lubrication
Load reduction
Replace the sliding friction force with the rolling friction force

V. Consolidation of what has been learned. Solving qualitative problems

Teacher: You have questions on your card to consolidate. Read them, answer them, you can consult with your desk neighbor.

Let's go back, guys, to the questions we asked at the beginning of the lesson. We will answer them.

Why are the needles carefully polished?
Answer: They reduce the force of sliding friction and then it is easier to sew.
What role does saliva play when swallowing food?
Answer: The role of lubrication, reduces friction and is easier to swallow.
Why does chalk leave a mark on a chalkboard?
Answer: When the chalk is pressed against the board, a large frictional force is created, which tears off the chalk particles - a mark appears on the board.

In the winter twilight, nanny's tales
Sasha loved. In the morning in the sled
Sasha sat down, flew like an arrow,
Full of happiness, from the icy mountain. N. A. Nekrasov (sliding friction force)

Vova rides along the edge of the forest
On your bike
And he's lucky with jam
Everyone's welcome. (rolling friction force)

Though the burden is heavy at times,
The cart is light on the move;
The dashing coachman, gray time,
Lucky will not get off the irradiation machine. A. S. Pushkin (rolling friction force)

Cat for Bug
Bug for granddaughter
Granddaughter for grandmother
Grandma for grandfather
Grandpa for the turnip
They pull and pull, but they can’t pull it out . (static friction force)

Teacher: Now let’s check how you can apply theory in practice. The last page of the information card suggests working on options.

VI. Running the test

Test work

Teacher: Take a pen and circle the correct answer.

Option 1

Option 2

1. In what units is friction force measured?
A. m
B. N
V. m/s

2. Which force is greater: the static friction force or the sliding friction force?
A. Fp.< Fск.
B. Fp. = Fsk.
IN. Fsk.< Fp.

3. Why do they put rollers under it when moving a heavy load?
A. to increase friction force
B. to reduce friction
B. the friction force does not change

4. During icy conditions, the sidewalks are sprinkled with sand, and the friction force of the shoe soles on the ice...
A. decreases
B. increases
V. does not change

1. What device can measure friction force?
A. ruler
B. beaker
B. dynamometer

2. Which force is smaller: the static friction force or the rolling friction force?
A. Fp.< Fк.
B. Fp. = Fк.
IN. Fk.< Fp.

3. Why does any body set in motion eventually stop?
A. the sliding friction force acts on the body
B. the rolling friction force acts on the body
B. the force of static friction acts on the body

4. When the car is slipping, gravel or slag is poured under the wheels. At the same time, the friction force...
A. decreases
B. increases
V. does not change

Teacher: Guys, take a pencil and exchange cards. We carry out mutual verification. The correct answer options are presented on the slide. Rate it taking into account the criterion, it is also indicated on the slide.

Right answers:

Question number	1	2	3	4
Option 1	B	IN	B	B
Option 2	IN	IN	A	B

Evaluation criteria:

score "5" for 5 correct answers
score “4” for 4 correct answers
score "3" for 3 correct answers

Have you checked? Raise your hand for a "5"? Lower it. And who needs “4”?

Well done! Well, the rest have something to work on.

The information card remains with you. You will paste it into your notebook.

VII. Summarizing.

Let's summarize: What new did you learn in the lesson?

Did you achieve your goals in the lesson?

House. exercise

§§ 30-32 (for everyone)
Come up with an essay on the topic “If the force of friction disappeared...” (for those interested)

Reflection

Self-esteem: Take the self-assessment sheet and answer the questions.

Self-assessment sheet

№	Question	Yes	No	I find it difficult to answer
1	I know the types of friction force
2	I know the unit of friction force
3	I know where the friction force is directed
4	I can determine the type of friction force
5	I can measure the force of friction
6	I consider my work in class to be effective

And just a second of attention, guys, in memory of this lesson, I want to give you a bookmark about the force of friction. I give them to you, and you answer the questions on the card.

Thank you for your cooperation!

The lesson is over.

Literature:

Grinchenko N. A. Problems with career guidance content for rural schools // Physics at school, 2001, No. 2.
Maron A. E., Maron E. A. Didactic materials. Physics 7th grade - M.: Bustard, 2002.
Peryshkin A.V. Physics. 7th grade – 3rd ed., rev. – M.: Bustard, 2000.
Perelman Ya. N. Entertaining physics. Book 1, 2 – M.: Nauka, 1991.

Open lesson on physics in 7th grade

Prepared by:

Teacher of the highest category

Tokarev A.A.

Subject: Friction force

Lesson Objectives :

Educational:

give the concept of friction force

know types of friction

be able to experimentally establish what the friction force depends on

Educational:

development of logical thinking, development of skills to experiment, formation of teachings to use instruments, formation of skills to draw conclusions, analyze and compare the results of experiments.

Educational:

to attract students to active independent activity, to form interaction in group work, to cultivate diligence, accuracy and clarity when answering, and the ability to see physics around them.

Equipment:

1. Computer, multimedia projector

2. Dynamometers, sheets of smooth paper, a set of weights, a wooden block, a roller, rubber on one side is smooth, on the other with a tread.

During the classes:

I. Organizational moment.

Hello guys! Glad to see you again! Let's continue to study physical phenomena! Sit down.

II . Updating knowledge and fixing difficulties in activities.

Nowadays the problem of slippery shoes is especially relevant, it also affected me (video is shown)

How to tighten a self-tapping screw or a screw that just won’t screw in? (experience demonstrated)

Door hinges squeak annoyingly...how to get rid of the squeak?

Can you help me solve these problems in class today?

Let's review the material we covered.

Questions:

What quantity is called force? (Physical quantity showing the measure of interaction between bodies )

What is the interaction of bodies? (Mutual action of two bodies on each other )

How is strength defined? (F )

Unit of force? (1 Newton )

How to calculate the force of gravity acting on a body of any mass? (You need 9.8 N/kg multiplied by the mass of this body )

What is body weight called? (Body weight is the force with which the body, due to attraction to the Earth, acts on a support or suspension )

How to calculate body weight? (Just like gravity )

What device is designed to measure force? (Dynamometer )

What needs to be done to determine the value of the instrument scale division? (You need to find the two nearest scale bars next to which the values of the quantity are written, subtract the smaller value from the larger value and divide the resulting number by the number of divisions between them)

Determine the price of the dynamometer division.

III. Setting a learning task

All of you guys had to sled and ski in winter. Why, when going down a hill, do we not go endlessly, but stop? What's stopping you from rolling further and further? Let's do an experiment. Let's put the typewriter on the table. What will we observe? How will the speed of the machine change? Why will she change? How is it directed? What prevents the movement of the car? (Friction force.) Let's write down the topic of today's lesson in our notebooks

Lesson topic: Friction force

Goal: To understand the concept of friction force

Learn to measure

Find out what it depends on

Be able to…………………formulate yourself

IY. Discovery of new knowledge

We will work according to plan.

Examples, facts

Definition

Causes of occurrence

Designation, image

…………. Formulate it yourself

Types of friction

What does it depend on

Application in life

We have a block on our table. Let's push him. The body stopped. Why, what is slowing him down?

(Friction, surfaces rub against each other and the body slows down)

A frictional force acts on a body, how is it directed?(Against traffic.)

The force that arises when one body moves on the surface of another, applied to the moving body and directed against the movement is called the friction force.

Reasons for the occurrence of friction force:

Roughness of the surfaces of contacting bodies.

Attraction of molecules of interacting bodies.

Guys, there are three types of friction:

P o r t a n t i o n S l i d i n g R a l i n g

What does friction force depend on:

Now we will carry out research work, the groups will receive tasks:

Comparison of friction and sliding forces

Study of the dependence of sliding friction force on the type of rubbing surfaces.

Study of the dependence of sliding friction force on pressure and on the area of rubbing surfaces.

Teacher: We have been familiar with the phenomenon of friction and friction force since childhood. The first studies of friction force were carried out by the great Italian scientist Leonardo da Vinci 400 years ago, but these works were not published.

Let's try to make up for them.

1.You have a block and a roller on your desk. Watch the video on how friction force is measured, measure the sliding and rolling friction force, compare them

Conclusion: The sliding friction force is greater than the rolling friction force.

The maximum static friction force is greater than the friction force

slip.

2.Compare the friction force of a wooden block on wood, on smooth rubber and on corrugated rubber.

Conclusion : Frictional force depends on the surface material

The rougher the surface, the greater the sliding friction force.

3.Explore the dependence of the friction force on the pressure force using the available sets of weights and on the surface area

Conclusion : The sliding friction force depends on the pressure force. How

The more loads, the greater the sliding friction force.

The friction force almost does not depend on the surface area; the dependence is not clearly visible.

Conclusion on the work:

The friction force depends:

From the force of gravity acting on the body;

From the material from which the bodies are made, and from the quality of their processing;

From the area of rubbing surfaces.

Thanks to the presence of friction in nature, life is possible in the form in which it exists on Earth. In some cases it is useful, in others it is harmful. But in order to subjugate friction you need to know how to increase and decrease the friction force

Did you go boating?

And on asphalt?!

Conclusion: Liquid friction is many times less than dry friction; lubrication reduces friction.

There is also dry graphite lubricant in your pencil, making it easy to draw with.

Y. Application of new knowledge. Problem solving.

Now let’s remember the problems at the beginning of the lesson and try to solve them.

We work in groups. Each group receives waybills. Groups take turns voicing their solutions to problems and turning in written answer sheets.

The teacher demonstrates his solutions to problems.

YI. Primary consolidation and control.

Executing test tasks: on a computer, the program gives a rating. (Virtual school of Cyril and Methodius. lessons 7th grade. Lesson 8)

Reflection on activity (lesson summary)

Raise your hands if you are satisfied with your work in class