Determination of the efficiency of an inclined plane. Laboratory work "Determination of the efficiency of an inclined plane."

1. Organizational moment. Slides 2-3

2. Actualization of knowledge. Warm up. Slides 4-7

1. What are simple mechanisms?

List what simple mechanisms you know.

Give examples of the application of simple mechanisms.

What are they needed for?

Explain in your own words the meaning of the phrase “gain a gain in strength.”

Formulate the "golden rule" of mechanics.

2. Consider the situation. Slides 8 - 9

A worker needs to load a barrel of gasoline into the back of a truck. To just lift it, you need to apply a very large force - a force equal to the gravity (weight) of the barrel. The worker cannot apply such a force.

. What should he do?

(students make their own suggestions)

... then he puts two boards on the edge of the body and rolls the barrel along the formed inclined plane, applying a force much less than the weight of the barrel!

Conclusion: Slide 10 - 11

· An inclined plane is used to move heavy objects to a higher level without directly lifting them.

· Such devices include ramps, escalators, conventional stairs and conveyors.

3. What parameters characterize the inclined plane?

3. Laboratory work No. 10. Slides 12 - 21

"Determination of the coefficient of efficiency when lifting a body along an inclined plane."

Learning new material.

Efficiency is a physical quantity equal to the ratio of useful work to spent work, expressed as a percentage.

Efficiency is indicated by the letter "this"

Efficiency is measured as a percentage.

What work is useful, what work is expended?

Work expended Aexpended=F*s

Useful work Auseful = P*h

for example , efficiency = 75%.

This number shows that out of 100% (work expended), useful work is 75%.

Job instruction.

Performing laboratory work.

Determine the price of division of instruments (dynamometer and ruler).

1. Install the board at height h, measure it.

2. Measure the weight of the bar P with a dynamometer.

Technological map of the lesson "Determining the efficiency of an inclined plane" lesson stage ( regulation, min .)

Teacher activity

Student activities

Cognitive

Communicative

Regulatory

Actions taken

Formed ways of activity

Actions taken

Formed ways of activity

Organizational (2 minutes.)

Greets students, notes those who are absent, checks the readiness of students for the lesson.

Knowledge update (8 min.)

Displays slide 2 of the presentation "Inclined Plane Efficiency". Reveals the question chosen by the student, comments on the answer given to him.

The students, one by one, choose the number of the question, answer it, the rest listen, analyze this answer.

The ability to consciously build a verbal statement in oral form, to structure knowledge.

If necessary, supplement or correct this answer to the question.

Ability to listen and engage in dialogue

express their thoughts, possession of monologue and dialogic forms of speech in accordance with the norms of their native language.

Control and evaluate their own knowledge, if necessary, correct them.

Development of the ability to mobilize forces and energy.

Creating a problem situation (4 min.)

Creates and invites students to find a way out of a problem situation:A worker needs to load a heavy barrel onto a ship. To do this, you need to apply a very large force - a force equal to the weight of the barrel. The worker cannot apply such a force.

Displays slide 3 (opens scene 5).

Asks a question:Is the energy expended by the worker only spent on lifting the load?

Displays slide 4 (opens scene 3).

The cognitive goal is singled out and formulated: to find a way to lift the body to a height using less force than the weight of the body.

Choose the most effective way to solve the problem: apply an inclined plane.

It is assumed that part of the energy is spent on overcoming the friction force.

They conclude that the less energy is spent on overcoming the friction force, the more effective a simple mechanism.

Statement and solution of the problem.

The choice of the most effective ways out of the problem situation, depending on the specific conditions

Putting forward an assumption about the existence of a physical quantity characterizing the efficiency of a simple mechanism.

Suggest a way out of the problem:

invite assistants, apply an inclined plane.

Ability to participate in a group discussion

Assess the ability to identify work to overcome gravity and friction, but do not know how to relate them to each other.

They set an educational task: to get acquainted with the physical quantity characterizing the efficiency of the inclined plane.

Setting a learning task based on the correlation of what is already known and what is still unknown to students.

Learning new material (8 min.)

Demonstrates the lifting of the body using an inclined plane, measures the weight of the body and the force of friction, the height and length of the inclined plane.

Displays on screen

slides 5-6.

Gives a characteristic of the efficiency of a simple mechanism.

Compare the weight of the body with the force of friction, the height of the inclined plane with its length.

They conclude that there is a gain in strength and a loss in distance when using an inclined plane.

Perform a drawing of an inclined plane with the designation of its length, height, write down the definition and calculation formula for the efficiency of a simple mechanism.

Formation of sign-symbolic UUD.

Ask a question about the units of measurement of the efficiency of an inclined plane

Development of the ability to accurately express one's thoughts in accordance with the norms of the native language.

They single out and realize what has already been learned (calculation of the work of force) and what is still to be learned (What work is considered useful, what is spent, how to calculate the efficiency of an inclined plane through work useful and spent)

Development of knowledge assessment.

Research practical work (17 min.)

Organizes discussion of the study plan.

Displays on screen

slides 7-11 of the presentation "Inclined Plane Efficiency".

Provides instructions on how to safely perform laboratory work.

Formulates a problematic question:on what parameters the efficiency of an inclined plane depends.

Distributes equipment kits, IOT, technological cards to groups of students

Provides assistance to groups of students in the performance of work.

Draw up a plan and sequence of actions to determine the efficiency of an inclined plane:

1. Measure the weight of the bar (P).

2. Measure the height of the inclined plane (h).

4. Measure the friction force (F tr ).

Measure the length of the inclined plane (l).

Independently formulate a cognitive task:

check how the efficiency of the inclined plane depends on the weight of the lifted body and the angle of the inclined plane?

They put forward a hypothesis: the efficiency of an inclined plane depends on the angle of inclination and does not depend on the weight of the body being lifted.

Independent creation of activity algorithms in solving search problems.

Independent formulation of a cognitive task.

Self-promotion of a hypothesis about the dependence of the efficiency of an inclined plane on the angle of inclination and the weight of the lifted body.

Control, if necessary, correct and evaluate the actions of a group partner.

Ability to integrate into a peer group and build productive collaborations with peers and adults

Carry out the drawn up action plan to determine the efficiency of the inclined plane:

1. Determine the division value of the dynamometer, protractor and measuring tape.

2. Assemble the installation.

2. Measure the weight of the bar (P).

3. Measure the height of the inclined plane (h).

4. Useful work is calculated using the formula.

5. Measure the friction force (F tr ).

6. Measure the length of the inclined plane (l).

7. Calculate the work expended using the formula

8. Calculate the efficiency of the inclined plane according to the formula

9. Change the weight of the bar, repeat 1-6.

10. Change the angle of the plane, repeat 1-6.

11. The results are entered in the table.

Ability to plan and sequence actions

predicting the result.

Reflection (4 min.)

Reminds that the conclusion of the work should be a response to the purpose of the study.

They draw up the results of the work, draw a conclusion, analyze the result.

Conscious construction of a speech statement in writing.

Reflection of methods and conditions of action, control and evaluation of the process and results of activities.

They conclude: in the course of laboratory work, the efficiency of an inclined plane at an angle of inclination of 20 to the horizon turned out to be 45%, it is always less than 100%, depends on the angle of inclination (the greater the angle of inclination of the plane, the greater its efficiency) and does not depend on the weight of the lifted body.

Ability to accurately express one's thoughts;

Evaluate the results of the work:

BUT P must be less than Az;

the height of the inclined plane must be less than its length, the resulting efficiency must be less than 100%.

If the result obtained is not correct, find an error in the measurement or calculation.

Ability to evaluate and control results

adjust the plan and method of action in case of discrepancy between the standard and the result obtained.

Homework (2 minutes.)

Displays slide 12.

physics teacher GOU lyceum No. 384 of the Kirovsky district of St. Petersburg

Introduction

The concept of "efficiency" is first introduced in the course of physics in the 7th grade. The use of modern educational technologies allows students to increase the motivation for learning and the efficiency of mastering the material.

When conducting the lesson "Determination of the efficiency when lifting the body on an inclined plane", the technology of research in training was used.

The lesson includes the following stages: updating knowledge, studying new material (performing laboratory work), conducting research, reflection.

During the lesson, work in pairs was used. The use of this technology allowed students not only to acquire new knowledge, but also to develop the ability for active creativity.

Goals and objectives of the lesson

Lesson objectives:

Updating students' knowledge

Generate interest in the material being studied

・Motivate students

Goals:

Tutorials:

· Introduce students to a new physical quantity - the efficiency of the mechanism.

Verify by experiment that the useful work done with the help of an inclined plane is less than the work expended.

Determine the efficiency when lifting a body on an inclined plane.

Find out what determines the efficiency when lifting a body-inclined plane.

· Check the ability to apply the acquired knowledge to solve practical and research problems.

Show the connection of the studied material with life.

Developing:

To create conditions for the development of the personality of students in the course of their activities.
To promote the development of practical skills and abilities.
Form the ability to put forward a hypothesis, test it.
To teach to highlight the main thing, to compare, to develop the ability to generalize, systematize the knowledge gained. Develop the ability to work in pairs.

Educational:

Development of communication skills.
Development of teamwork skills (mutual respect, mutual assistance and support).

Health saving:

Building a model of a health-saving lesson.

Lesson Form: Research work of students.

During the classes

· Organizing time.

· Updating knowledge. Warm up.

· Perform laboratory work.

· Physical pause.

· Research part of the work.

· Homework.

Consolidation of the studied material.

Subject of study: inclined plane.

Compare useful and expended work.

Equipment:Computer, multimedia projector (for teachers)

· A set of cargoes

· Dynamometer

Measuring tape (ruler)

1. Introduce students to a new physical quantity - the efficiency of the mechanism.

Conclusion:

3. Place the block on the board and use a dynamometer to pull it evenly up along the inclined plane. Measure the force F. Remember how to use the dynamometer correctly.

4. Measure the length of the inclined plane s.

5. Calculate useful and expended work.

6. Calculate the efficiency when lifting the body on an inclined plane.

7. Write down the data in table No. 1.

8. Draw a conclusion.

Registration of work results

Table 1.



Conclusion:

Useful work _______________ than expended.

Efficiency when lifting a body along an inclined plane _____%, i.e. this number indicates that _______________________________________________________________.

4. Physical break. Slides 22 - 25

Inclined plane examples. Students watch slides with examples of the use of an inclined plane.

5. Research. Slides 26 - 30

Problem. What influences the efficiency of an inclined plane?

Hypothesis. If you increase (decrease) the height of the inclined plane, then the efficiency when lifting the body along the inclined plane will not change (increase, decrease).

If you increase (decrease) the weight of the body, then the efficiency when lifting the body along an inclined plane will not change (increase, decrease).

Students choose one of the proposed research options:

from the height of the inclined plane?

How does the efficiency of lifting a body down an inclined plane depend? from body weight?

Registration of work results

Table 2.

The efficiency when lifting a body along an inclined plane depends (does not depend) on the height of the inclined plane. The greater (less) the height of the inclined plane, the more efficient __________.

The efficiency when lifting a body along an inclined plane depends (does not depend) on the weight of the body. The more (less) body weight, the more efficient __________.

Discussion of research options.

6. Homework. Slides 31 - 32

Paragraph 60, 61, task 474.

For those who wish to prepare messages.

Simple mechanisms in my house

Meat grinder device

Simple mechanisms in the country

Simple mechanisms in construction

Simple mechanisms and the human body

7. Consolidation of the studied material Slides 31 - 34
Work with text

When using _________________ mechanisms, a person commits _______________. Simple mechanisms allow you to win ______________. At the same time, how many times ________________ is in force, the same number of times _________________________________. This is the ______________________ of mechanics. It is formulated as follows: ________________________________________________________________________________________________________________________________________________. Usually, when a body moves, ______________________________ friction. Therefore, the value of _____________________ of work is always greater than ____________________. The ratio of ________________________________________ to ______________________, expressed as a percentage, is called _________________________________________________________________________________________: ______________.

Mini test.

Your efficiency today in the lesson

2. more than 100%

3. less than 100%

Literature

1 A.V. Peryshkin Physics Grade 7. Moscow: Bustard, 2010

2 G.N. Stepanova Physics 7 workbook part 1. St. Petersburg STP-School, 2003

Technological map of the lesson physics in 7th grade.

Laboratory work No. 11 "Determining the efficiency when lifting a body along an inclined plane."

Subject		Laboratory work No. 11 "Determining the efficiency when lifting a body along an inclined plane."
Lesson type:		A lesson in the formation of initial subject skills.
Target		to ensure the development of skills for measuring efficiency when lifting a body along an inclined plane.
Tasks		Educational: 1. working with the textbook material and doing laboratory work, find out how to determine the efficiency when lifting a body along an inclined plane; 2. be convinced by experience that useful work is less than complete work; 3. to deepen the theoretical and practical knowledge gained in the study of the topics "Work", "Simple mechanisms", "Efficiency". Developing: 1. awaken curiosity and initiative, develop a steady interest of students in the subject; 2. expressing his opinion and discussing this problem to develop students' ability to speak, analyze, draw conclusions. 3. contribute to the acquisition of the necessary skills for independent learning activities. Educational: 1. during the lesson, to promote the education of students' confidence in the cognizability of the world around them; 2. working in pairs of permanent composition, when performing experimental tasks and discussing the problem, to educate the communicative culture of schoolchildren.
Planned result. metasubject results. 1. the formation of cognitive interests aimed at developing ideas about simple mechanisms; 2. ability to work with sources of information, including experiment; 3. the ability to convert information from one form to another. Subject results. 1. be able to use a ruler and a dynamometer to measure physical quantities. 2. be able to express measurement results in SI units.		Personal. Conscious, respectful and benevolent attitude towards another person, his opinion; willingness and ability to engage in dialogue with other people and achieve mutual understanding in it. Cognitive. Identify and formulate a cognitive goal. Build logical chains of reasoning. Produce analysis and transformation of information. Regulatory. Ability to plan research; identify potential difficulties in solving the educational problem; describe your experience, plan and adjust. Communicative. Ability to organize educational cooperation and joint activities with the teacher and peers; work individually and in a group: find a common solution and resolve conflicts based on the coordination of positions and consideration of interests.
Basic concepts of the topic		Total work, useful work, efficiency, simple mechanisms, inclined plane.
Space organization
The main types of educational activities of students.	Core technologies.		Basic methods.	Work forms.	Resources.Equipment.
1. Listening to the teacher's explanations. 2. Independent work with the textbook. 3. Performing frontal laboratory work. 4. Work with handouts. 5. Measurement of quantities.	collaboration technology.		1. verbal; 2. visual; 3.practical.	Individual, general class, in pairs of permanent composition.	Physical hardware: board, ruler, dynamometer, bar, tripod with clutch and foot. Resources: tests, projector, presentation.

Structure and course of the lesson.

	Lesson stage	Stage tasks	Activity teachers	Activity student		Time
Introductory-motivational stage.
	Organizational stage	Psychological preparation for communication.	Provides a favorable mood.	Getting ready for work.	Personal
	Analysis of independent works on the topic "Levers".	Work on bugs.	Problem solving.	They solve problems.
	Stage of motivation and updating of knowledge(determining the topic of the lesson and the joint goal of the activity).	Provide activities to define the objectives of the lesson.	Offers puzzles "Think and guess", offers to name the topic of the lesson, determine the goal.	They try to answer, solve problems. Determine the theme of the lesson and the purpose.	Personal, cognitive, regulatory

Operational and content stage
	Learning new material. 1) Updating knowledge. 2) Primary assimilation of new knowledge. 3) Initial check of understanding 4) Control of assimilation, discussion of the mistakes made and their correction.	To promote the activities of students in independent study of the material.	Offers to organize activities according to the proposed tasks. 1) Offers to recall the concept of efficiency. 2) Briefing on the performance of work. Explanation of theoretical material. 3) Offers to perform experimental tasks. 4) offers to draw conclusions.	The study of new material on the basis of independent laboratory work. 1) Answer. 2) Listen. 3) Perform the proposed experimental tasks. 4) Answer questions. 5) Draw conclusions. Discuss.	Personal, cognitive, regulatory
Reflective-evaluative stage.
	Reflection. (Summarizing).	An adequate self-assessment of the individual, his capabilities and abilities, advantages and limitations is formed.	Prompts you to select an offer.	Answer.	Personal, cognitive, regulatory
	Submission of homework.	Consolidation of the studied material.	Writing on the board.	Recorded in a diary.	Personal

Appendix.

1. Analysis of independent work on the topic "Levers".

Work on bugs.

Slide number 2.

a) Figure (a) shows a disk fixed on axis O. Forces F and F1 are applied to the disk. Name the shoulders of forces.

b) In figure (b), a person using a lever lifts a stone weighing 600 N. With what force does a person act on the lever if AB \u003d 1.2 m, BC \u003d 0.5 m.

c) In figure (c), a weight of 20N is placed on a ruler, one end of which rests on the table, and the other is held by a dynamometer. Determine the readings of the dynamometer if the length AC = 1m, BC = 25 cm.

Slide number 3.

a) The figure shows a triangular plate fixed on an axis passing through the point O. Forces F and F1 are applied to the plate. Name the shoulders of forces.

b) A person with a stick holds a bucket of water weighing 120 N. The end of the stick is on a support, while AC = 120 cm, BC = 30 cm. What force does the person apply to support the bucket?

2. Motivational stage.

Slide number 4.

Problems "Think and guess."
1. This is not only a simple mechanism, but also a military alliance.
2. This is a mechanism at the well, and a shirt detail.
3. In this city near Moscow, there is a house - a museum of P.I. Tchaikovsky.
Answers.

1. block
2. gate
3. wedge

Slide number 5.

What other simple mechanisms do you know? Why are they called that?

Inclined plane, block and lever-

We cannot do without them.

3. Learning new material.

Slide number 6-7.

An inclined plane is the simplest mechanical device used to lift heavy objects in order to gain strength.

Inclined plane- a simple mechanism in the form of a flat surface mounted at an angle other than a straight line to a horizontal surface.

Slide number 8-10.

The characteristic of the mechanism, which determines what proportion of useful work is from the total, is called the coefficient of performance - efficiency.

Slide number 11. Invite students to position the inclined plane at different heights. After carrying out the experiment and calculations, compare the obtained data.

Action plan for determining the efficiency of an inclined plane:

Measure the weight of the bar (P).

Measure the height of the inclined plane (h).

Measure the friction force (Ftr).

Measure the length of the inclined plane (l).

8. Draw up the results of the work and draw conclusions.

Slide number 12.

Findings:

1. Useful work is less than total work.

2. The height of the inclined plane must be less than its length.

3. Efficiency less than 100%. (At an angle of inclination of 20° to the horizon it is equal to 45%).

4. The efficiency of the inclined plane depends on the angle of inclination. The greater the angle of inclination of the plane, the greater its efficiency.

Slide number 13.

Reflection. How did I work in class? Choose an offer.

Back forward

Attention! The slide preview is for informational purposes only and may not represent the full extent of the presentation. If you are interested in this work, please download the full version.

Thing:	Physics.
Class:	7th grade.
Textbook:	Peryshkin, A. V. Physics. 7 cells [Text]: textbook. for general education educational institutions / A. V. Peryshkin, - M .: Bustard, 2010. - 192 p.
Lesson topic:	Determination of the efficiency of an inclined plane.
The purpose of the lesson:	Acquaintance of students with a new physical quantity - the efficiency of the mechanism.
Lesson objectives:	Educational: Define the efficiency of a mechanism. Verify by experiment that the useful work done with the help of an inclined plane is less than the work expended. Determine the efficiency when lifting the body on an inclined plane. Find out what determines the efficiency when lifting a body along an inclined plane. Show the connection of the studied material with life. Educational: To create conditions for the development of the personality of students in the course of their activities. To promote the development of practical skills for measuring force using a dynamometer, performing an experiment scheme. Continue the formation of the ability to highlight the main thing, put forward a hypothesis and test it experimentally. Educational: Continue developing communication skills of working in a team (mutual respect, mutual assistance and support).
Planned results:	subject: students will learn how to measure the characteristics of an inclined plane, calculate the useful and expended work, the efficiency of a simple mechanism; find out that the useful work is always less than the expended and, therefore, the efficiency is less than 100% and does not depend on the weight of the body being lifted, but it can be increased by increasing the angle of inclination of the plane to the horizon. Formed UUD: Personal: the establishment by students of a connection between the purpose of educational activity and its motive (meaning formation). Regulatory: Development of the ability to mobilize forces and energy. The ability to set a learning problem based on the correlation of known and unknown material, predicting the result, Drawing up a plan and sequence of actions, evaluating and monitoring the result obtained, adjusting the plan and methods of action in case of a discrepancy between the standard and the result obtained. Communicative: the ability to listen, participate in a collective discussion of a problem, enter into a dialogue, accurately express one's thoughts, mastery of monologue and dialogic forms of speech in accordance with the norms of the native language, integrate into a peer group and build productive cooperation with peers and adults. cognitive: The ability to consciously build a speech statement in oral and written form, to structure knowledge. Statement and solution of the problem, the choice of the most effective ways out of the problem situation, depending on the specific conditions, the creation of activity algorithms for solving search problems. Formation of sign-symbolic UUD. Independent formulation of a cognitive goal, hypotheses. Reflection of methods and conditions of action, control and evaluation of the process and results of activities. Extraction of necessary information.
Lesson type:	A lesson in developing special skills and abilities.
Lesson form:	Research work of students.
Equipment:	Computer, projector, screen. A set of instruments for performing laboratory work: a guide rail, a dynamometer, a measuring tape, a bar, a weight of 100 g, a tripod with a clutch and a foot (14 pcs.).
Materials for the lesson	Instructions on labor protection when performing laboratory work "Measuring the efficiency when lifting the body on an inclined plane" (14 pcs.) ( *Appendix 1* ). Technological map of the laboratory work "Measuring the efficiency when lifting the body on an inclined plane" (14 pcs.) ( *Annex 2* ). Technological map of the lesson ( *Annex 3* ).
Author's media product:	The presentation "Determining the efficiency of an inclined plane", made in Microsoft PowerPoint 2010, consists of 28 slides, including the title one.
Software:	MS Office 2010, KMPlayer or other program that supports swf files.

The scenario of the lesson consists of seven stages.

1. Organizational(2 min.): The teacher marks the students who are absent from the lesson, reminds those present at the lesson that they continue to study simple mechanisms and already know their definition, types, the “Golden Rule” of mechanics, the lever balance rule, and today the children can get acquainted with one more characteristic of a simple mechanism, but after they open the message closed by puzzles.

2. Updating knowledge(8 min.): The teacher displays slide 2 of the presentation for the lesson "Determining the efficiency of an inclined plane." The program is designed as follows: by clicking the mouse exactly on the number of the question, a slide with the question itself is opened, the text of the question is placed on it. You can check the correctness of the answer by clicking the mouse. Using the control button, you can return to slide No. 2. By clicking on the field of a correctly answered question, the puzzle is removed and part of the message is opened. The next question is selected and everything repeats. It is more interesting to choose questions in an arbitrary order. After answering the last question, a message to the guys opens on the screen: “Tell me and I will forget. Show me and I will remember. Let me do it myself and I will learn!”

3. Creating a problem situation(4 min.): The teacher creates and invites students to find a way out of the problem situation: the worker needs to load a heavy barrel onto the ship, but to do this, a very large force must be applied - a force equal to the weight of the barrel. The worker cannot apply such a force. The guys suggest using an inclined plane. The teacher displays slide 3 of the presentation for the lesson “Determining the efficiency of an inclined plane” (a flash model of the Unified Collection of the DER “Simple mechanisms. Inclined plane” is inserted on it), reveals scene 5. asks a question: Is it only the energy expended by the worker that is spent on lifting the load? Students assume that part of the energy is spent on overcoming the force of friction. The teacher displays slide 4 of the presentation for the lesson “Determining the efficiency of an inclined plane”, (a flash model of the Unified collection of the DER “Efficiency of a mechanism” is inserted on it), reveals scene 3. The question of the possibility of a different ratio of work done by the mechanism is discussed , and the energy that is spent to overcome the friction force. Students make assumptions about the existence of a physical quantity that characterizes the effectiveness of a simple mechanism.

4. Learning new material(8 min.): The teacher demonstrates lifting the body using an inclined plane, measures the weight of the body and the force of friction, the height and length of the inclined plane. Students compare the weight of the body with the force of friction, the height of the inclined plane with its length, draw a conclusion about the gain in strength and loss in distance when using the inclined plane. The teacher displays slides 5-6 of the presentation for the lesson “Determination of the efficiency of an inclined plane”, characterizes the efficiency of a simple mechanism. Students make a drawing of an inclined plane with the designation of its length, height, write down the definition and calculation formula for the efficiency of a simple mechanism.

5. Research practical work a (17 min.): The teacher facilitates a discussion of the research plan. Students draw up a plan and sequence of actions to determine the efficiency of an inclined plane:

The teacher displays slides 7-11 of the presentation for the lesson "Determination of the efficiency of an inclined plane", instructs on the safe performance of laboratory work, formulates a problematic question: on what parameters the efficiency of an inclined plane depends. Students independently formulate a cognitive task: to check how the efficiency of the inclined plane depends on the weight of the lifted body and the angle of the inclined plane? They put forward a hypothesis: the efficiency of an inclined plane depends on the angle of inclination and does not depend on the weight of the body being lifted.

The teacher distributes to the students sets of instruments for performing laboratory work, instructions for labor protection ( Appendix 1 ), technological map for the implementation of laboratory work No. 14 "Measurement of efficiency when lifting a body along an inclined plane" ( Annex 2 ), assists groups of students in the performance of work. Students perform laboratory work at different angles of inclination of the plane to the horizon and different weights of the lifted load.

6. Reflection(4 min.): Students evaluate and analyze the results of their work: Ap should be less than Az; the height of the inclined plane must be less than its length, the resulting efficiency must be less than 100%. If the result obtained is not correct, find an error in the measurement or calculation. They draw up the results of the work, conclude: in the course of laboratory work, the efficiency of an inclined plane at an angle of inclination of 20 ° to the horizon turned out to be 45%, it is always less than 100%, depends on the angle of inclination (the greater the angle of inclination of the plane, the greater its efficiency) and not depends on the weight of the lifted body.

7. Homework(2 min.): The teacher displays slide 12 of the presentation for the lesson “Determining the efficiency of an inclined plane”, voices, comments, and makes recommendations for effective homework:

§ 61;
Prepare messages (optional):
Simple mechanisms at home, in the country.
Simple mechanisms in construction.
Simple mechanisms and the human body.

Addresses of used Internet resources

Laboratory work number 6.

Determining the efficiency of an inclined plane

Objective:

1. calculate the efficiency of the proposed inclined plane and draw a conclusion about its value;

2. verify by experience that Ap< Аз.

Equipment: dynamometer, board, tripod, wooden block, measuring tape (or ruler), set of weights (fig.).

Working process:

1. Determine the division value of measuring instruments. Cd \u003d .... N. (dynamometer)

Cl = .... N. (rulers).

2. Using a dynamometer, determine the weight of the bar (R), lifting it up h(write in the table).

3. Moving the bar at a constant speed up the inclined plane, measure the traction force required for this (F). (write in table)

4. Use the ruler to define the path s passed by the lower edge of the load, and the height h on which it was raised. (write in table)

5. Determine the total weight of the bar with two weights (R), (write in the table).

6. Loading the bar with two weights and attaching a dynamometer to it, move the bar at a constant speed up the inclined plane. Measure the traction force required for this ( F). s and h the same. (to table)

7. Lower the plank below and repeat experiment 2. S the same , h measure (record in a table)

general task for 3 experiments:

8. Calculate useful and expended work: ,

9. Find the efficiency of the inclined plane.

10. Enter the results of the calculations in the table.

Conclusion: as a result of the work, we