The lesson on the formation of experimental skills has the following goals:

• teaching - to form the concepts of the rule and the condition of equilibrium, the rule of moments, to show its significance in science; be able to explain the rules for applying leverage and apply them to explain results practical work;
• developing - show students the social and practical significance the material being studied, to form the ability to generalize experimental data, to compare and draw conclusions,
• educational - to cultivate a culture of mental work, to continue work on the formation of communication skills, positive motivation for learning, aesthetic perception of the world, to instill a love for science and knowledge.

Equipment for the lesson: a computer, a projector, a lever on a tripod, a set of weights, a ruler.

During the classes:

I. Motivation.

1. What rules did we meet in the last lesson?

(- the rule of the lever and the rule of moments).

2. What do you need to know to write down these rules?

(- shoulder and strength)

3.Write down these rules.

Moment rule: M 1 = M 2;

Lever rules: F 1 *L 1 = F 2 *L 2

4. In what very familiar and often used devices do we find levers?

(scissors, wire cutters, lever scales).

II. Actualization of basic knowledge.

1. Explain the purpose of these objects (projection of drawings on the board).

• Scissors for cutting paper sheets.
• Scissors for cutting metal sheets.
• Lever scales for determining body weight.

2. Why do some scissors cut a thick layer of paper, while others do not?

Scissors operate on the basis of the lever balance rule. By applying a small force on the long part of the scissors on one side, we get a large force on the short part of the scissors on the other side. In order for scissors to cut a thick layer of paper or cardboard, their blades are made short and the handles long.

3. Apply and explain the rules for each of these items:

a) the length of the handle and the length of the blade of scissors for cutting paper are almost the same because it does not require much effort;

b) long handles and short blades of scissors for cutting metal sheets create a large force at the point of contact between the blade of the scissors and the metal; how many times they are shorter, the same number of times greater the force arising from the application;

c) lever scales have the same shoulders, which means that the force acting on the left and right sides of the scales is the same. Knowing the mass of the weights, determine the mass of the load.

III. Laboratory work No. 5 "Clarification of the conditions for the equilibrium of the lever"

(for three options):

1 option: L 1 =18cm; F 1 =2 N; F 2 =3H; L2=?

Option 2:L 1 =12cm; F 1 =2H; F 2 =3H; L2=?

3 option: L 1 =18cm; F 1 =1H; F 2 =3H; L2=?

Instructions for work:

1.Fix the lever on the tripod.

2. Balance the lever without weights using special bolts.

3. Balance the lever using a set of weights and a ruler according to the task of your option.

4. Draw a balanced lever on the diagram.

5. Measure the length of the shoulder L 2.

6. Determine the moments of forces M1 and M2.

7. Compare the value of M1 and M2.

8. Make a conclusion.

IV. Summarizing.

1. Conclusion about the validity of the rule of moments.

(Report from each option).

Placing sets of weights at the specified distance, we got the following result:

the product of the force on the shoulder of this force on the left side of the lever and on the right side of the lever is the same.

This means that the equilibrium condition is satisfied, the moment of force is the same.

General conclusion from the experiment:

Using different sets of weights in all groups performing the variant practical task, the following result was obtained: the products of the force on the shoulder of this force on the left side of the lever and on the right side of the lever are the same.

Therefore, the equilibrium condition of the lever is satisfied, the rule of moments is valid. M1= M2.

2. Questionnaire for reflection.

Full text of the material Development of a physics lesson

Lesson development (lesson notes)

Line UMK A. V. Peryshkin. Physics (7-9)

Attention! The site administration site is not responsible for the content methodological developments, as well as for compliance with the development of the Federal State Educational Standard.

Lesson type: combined.

Conduct forms: collective work with the whole class, work in groups, individual work.

Methods: conversation, story, laboratory work to determine the equilibrium condition of the lever.

The purpose of the lesson: to study the simplest and most common simple mechanism - the lever.

Lesson objectives:

• Educational: to consolidate the concepts of simple mechanisms, leverage and their role in human life; find out the condition of balance of the lever, teach to apply the rule of balance of the lever.
• Educational: educate cognitive interest to new knowledge, to create conditions for the manifestation of the desire to independently search for new knowledge.
• Developing: continue the development of skills to analyze knowledge and draw conclusions, develop attention, observation through a change in learning activities.
• to form practical skills in the use of instruments;
• develop creative thinking students.

Equipment: computer, projector, ruler lever, set of weights, scissors, lever scales, block, human skeleton, inclined plane.

During the classes

1. Organizational moment (2min)

2. Repetition. Knowledge update. (20 minutes)

A) demonstration: scissors, lever scales, block, lever-ruler, human skeleton. (2 minutes)

Students are asked a problematic question: What unites these devices and devices? (Simple mechanisms - levers, inclined plane)

Name these simple mechanisms, what kind of levers do they belong to?

b) Answer the questions:(5 minutes)

• What are simple mechanisms and what are they for?
• What is a lever (1st kind, 2nd kind)?
• What is a shoulder?
• Lever balance rule?
• What is a moment of force?
• What is the rule of moments?

B) Making a presentation.(9 min)

• Make a block diagram of the varieties of simple mechanisms. (3 min)
• Divide simple mechanisms into two groups. (5 min)
• Examination. (criteria presented in the presentation) (1 min)

D) The use of simple mechanisms - levers.(4 min)

Work in mini-groups (2 people) with elements of a game-competition.

Each group is given a sheet with a picture of a human skeleton, and there is a demonstration model on the table.

Task: in 1 minute, circle all possible levers using the example of a human skeleton.

At the end of the time, the groups change sheets and the number of circled levers is counted (the criteria are presented in the presentation). Three winners are selected most). Works are being collected. (self-assessment + teacher assessment)

When discussing together, the layout shows all possible levers.

3. Performing laboratory work. (18 min)

(Children are given printouts that they fill out as they work)

Objective: to check by experience at what ratio of forces and their arms the lever is in equilibrium. Experiment with the rule of moments.

Working process:

1. Hang one load on the hook on the right side at a distance of 12 cm from the axis.
2. Balance the lever with one weight. Measure your left shoulder.
3. Balance the lever again, but with two weights. Measure your left shoulder.
4. Balance the lever again, but with three weights. Measure your left shoulder.
5. Assuming that each load weighs 1 N, I write down the data and measured values ​​​​in the table.

	Force F 1 on the left side of the lever, N	Shoulder l 1 cm	Force F 2 on the right side of the lever, N	Shoulder l 2 cm	The ratio of forces and shoulders

1. Calculate the ratio of forces and the ratio of the shoulders for each of the experiments and write the results in the last column of the table.
2. Check whether the results of the experiments confirm the equilibrium condition of the lever under the action of forces applied to it and the rule of moments of forces.

(F₁)/(F₂)=(l₂)/(l₁).

M 1 \u003d F 1 * l 1 \u003d \u003d H / m

M 2 \u003d F 2 * l 2 \u003d \u003d N / m

7. Make a conclusion.

Conclusion: … .

4. The result of the lesson. (1 min.)

Conclusion: How many times the strength increased, how many times the shoulder decreased. When the moments of forces are equal, rotating the lever clockwise and counterclockwise, it is in equilibrium.

5. Homework.

(given to each individually at the end of the lesson) (1 min)

1. § 60, exercise 30(1-3.5).
2. Task (p. 180) *,
3. * Measure the arms of the lever (scissors, wrench, nail puller, metal shears) with a ruler and determine the gain in strength of the selected simple mechanisms.

6. Reflection. (on received leaflets) (3 min)

Method of non-judgmental control "Mini-review".

Write in one sentence:

• on one side of the “Important” sheet (what was important at the lesson today),
• on the other - "Unclear" (what remained unclear).

Objective: to check by experience at what ratio of forces and their arms the lever is in equilibrium. Experiment with the rule of moments.

From the textbook (§§56, 57) you remember that if the forces acting on the lever are inversely proportional to the arms of these forces, the lever is in equilibrium.

The product of the force on its shoulder is called the moment of force.

M 1 - moment of force F 1; M 2 - moment of force F 2;

Work example:

Calculations:

If, in the course of work, the ratios of the shoulders of forces turn out to be not quite equal to the ratios of forces, do not be embarrassed. The lever you are using is not a very accurate instrument, and even when measuring the shoulders and forces, some error can be made. So if the equality you get is approximate, this is enough to draw the correct conclusion.

Additional task.

The dynamometer will show the value of the force F 2 ≅1 N.

The forces acting on the lever in this case will be directed as follows: Force F 1 (gravity acting on the weights) will be directed vertically downward, its arm l 1 \u003d 15 cm.

Force F 2 (the force of elasticity of the dynamometer spring) will be directed vertically upwards; her shoulder l 2 = 15 cm.

1. Triune Purpose:

1.1 tutorial: create conditions for students to find out the conditions for the balance of the lever.
1.2 developing: to expand the natural science system of views on the processes occurring in nature.
1.3 nurturing: form on this educational material mental, moral, aesthetic, universal worldview, the development of independence in putting forward a hypothesis and formulating conclusions, to cultivate a communicative culture, the ability to evaluate oneself and one's comrades.

2. Tasks:

2.1. Learning objectives aimed at achieving personal results learning.
2.1.1. To promote self-development and self-education of students on the basis of motivation for learning and cognition.
2.1.2. Continue the development of students' speech, visual memory, attention, semantic memory, observation, visual perception, the ability to analyze, compare, generalize, and form an idea of ​​a computer as a learning tool.
2.1.3. Form a complete picture of the world.
2.1.4. To form a conscious, respectful and benevolent attitude towards another person, his opinion.
2.1.5. To form the ability to control the process and the result of activity.
2.2. Educational tasks aimed at achieving mathematical-subject learning outcomes.
2.2.1. Cognitive: to develop cognitive activity, continue to work on the formation of the ability to collect, systematize and apply information on the topic, apply and transform sign-symbolic means to solve problems.
2.2.2. Communicative: to continue work on the formation of the ability to work in pairs, organize educational cooperation and joint activities with the teacher and peers.
2.2.3. Regulatory: to continue work on the formation of the ability to independently plan ways to achieve goals, to consciously choose effective ways problem solving.
2.3. Learning objectives aimed at achieving subject learning outcomes.
2.3.1. To continue the formation of general educational and general cultural skills of working with information, the skill of applying formulas in practice. Understand the meaning of the concepts of the shoulder of force, the moment of force, the physical magnitude of the force, their units of measurement.
2.3.2. To be able to describe and explain physical phenomena on the basis of the balance condition of the lever.
2.3.3. Submit results strength measurements, shoulder strength using tables.
2.3.4. Draw conclusions based on experimental data.
2.3.5. give examples practical application lever.
2.3.6. Solve problems on the application of the equilibrium condition of the lever, the moment of force.
2.3.7. To check by experience at what ratio of forces and their arms the lever is in balance.
2.3.8. Experiment with the rule of moments.