I. A. Izyumov,
, Municipal Educational Institution Gymnasium No. 3, Aksai, Rostov region.
Efficiency measurement inclined plane
Impossible to have a direct hit from the experiment
into a narrowly defined theoretical target.
Imre Lakatos
When theory matches experiment,
This is no longer an opening, but a closing.
Pyotr Leonidovich Kapitsa
The purpose of the lesson: developing the ability to independently apply knowledge and transfer it to new conditions.
Didactic task: ensuring the assimilation of new knowledge and methods of action at the level of application in various situations.
Reflective activity of the student: self-affirmation, self-realization and self-regulation.
D Teacher’s activities to ensure reflection: presentation of educational material taking into account the zone of proximal and current development of the student.
Indicators of the actual result of solving the problem: independent completion of tasks using knowledge in various situations.
Logic of lesson construction: updating a body of knowledge → application of knowledge in various situations → control and self-control.
Equipment: wooden board, wooden block, dynamometer, measuring ruler.
During the classes
I. Updating the body of knowledge(15 minutes)
There is a reference drawing on the board. The teacher together with the students solves the problem:
How much work must be done to drag a load along a plane with an inclination angle of 30° to a height of 2 m, applying a force coinciding in direction with the displacement? Cargo mass 400 kg, friction coefficient 0.3. What is the efficiency of this?
Solution
II. Problem solving(30 min)
1 (10 min). The teacher and the class solve the problem:
Place a small object (rubber band, coin, etc.) on the ruler. Gradually lift the end of the ruler until the object begins to slide. Measure the height h and base b the resulting inclined plane and calculate the coefficient of friction.
Solution. F T x = F tr x ; mg sinα = μ F t cosα; μ = tanα = h/b.
Having received the calculation formula, students, using a wooden board, a wooden block and a ruler, experimentally determine the friction coefficient themselves and write down the result in their workbooks.
2 (10 min). The teacher and the class solve the problem:
Find the efficiency of an inclined plane 1 m long and 0.6 m high if the coefficient of friction when a body moves along it is 0.1.
Solution. Using the second result of solving the problem, we obtain:
The teacher suggests measuring the length of a wooden board and determining the efficiency of the inclined plane for the values of height and coefficient of friction obtained when solving the problem. The result is written down in a notebook.
3 (10 min). The teacher suggests determining the efficiency of an inclined plane for the height value obtained when solving the problem in one more way, and then comparing the results obtained and drawing conclusions.
Place the block on an inclined plane; Having attached a dynamometer to it, pull it evenly up along the inclined plane; measure the traction force F .
Measure gravity using a dynamometer F t acting on the block, and find the experimental value of the efficiency of the inclined plane:
Homework . Calculate the maximum possible gain in force obtained for a given plane inclination: k max = l/h.
Find experimentally the gain in force obtained using an inclined plane: k uh = F T /F.
Compare your results. Draw conclusions.
Literature
- Rymkevich A.P. Physics. Problem book-10–11: A manual for general education. institutions. – M.: Bustard, 2004.
- Dik Yu.I., Kabardin O.F., Orlov V.A., Kabardina S.I., Nikiforov G.G., Shefer N.I. Physics workshop for classes with angle. studying physics: Didact. material: grades 9–11: Ed. Yu.I. Dika, O.F. Kabardina. – M.: Education, 1993.
Technological lesson map in physics in 7th grade.
Laboratory work No. 11 “Determination of efficiency when lifting a body along an inclined plane.”
| Subject | Laboratory work No. 11 “Determination of efficiency when lifting a body along an inclined plane.” |
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| Lesson type: | Lesson in the formation of initial subject skills. |
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| Target | provide training in efficiency measurement skills when lifting a body on an inclined plane. |
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| Tasks | Educational: 1. working with the textbook material and performing laboratory work, find out ways to determine the efficiency when lifting a body along an inclined plane; 2. verify from experience that useful work is less than full work; 3. deepen the theoretical and practical knowledge gained from studying the topics “Work”, “Simple Mechanisms”, “Efficiency”. Educational: 1. awaken curiosity and initiative, develop students’ sustained interest in the subject; 2. by expressing their opinion and discussing this problem, develop students’ ability to speak, analyze, and draw conclusions. 3.promote the acquisition of necessary independent skills educational activities. Educational: 1. during the lesson, help develop students’ confidence in the knowability of the world around them; 2.working in pairs of permanent composition, when performing experimental tasks and discussing problems, to cultivate a communicative culture among schoolchildren. |
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| Planned result. Meta-subject results. 1.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 friendly attitude towards another person, his opinion; willingness and ability to conduct dialogue with other people and achieve mutual understanding in it. Cognitive. Identify and formulate a cognitive goal. Build logical chains of reasoning. Analyze and transform information. Regulatory. Ability to draw up a research plan; identify potential difficulties when solving educational problems; 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 coordinating positions and taking into account interests. |
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| Basic concepts of the topic | Complete work, useful work, efficiency, simple mechanisms, inclined plane. |
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| Organization of space |
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| Main types of educational activities of students. | Basic technologies. | Basic methods. | Forms of work. | Resources.Equipment. |
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| 1. Listening to the teacher’s explanations. 2.Independent work with the textbook. 3. Performing a frontal laboratory work. 4.Work with handouts. 5.Measurement of quantities. | Collaboration technology. | 1.verbal; 2.visual; 3.practical. | Individual, whole class, in pairs of constant composition. | Physical equipment: board, ruler, dynamometer, block, tripod with coupling and foot. Resources: tests, projector, presentation. |
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Structure and course of the lesson.
| Lesson stage | Stage tasks | Activity teachers | Activity student | Time |
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| Introductory and motivational stage. |
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| Organizational stage | Psychological preparation for communication. | Provides a favorable mood. | Getting ready for work. | Personal | ||
| Analysis of independent work on the topic “Levers”. | Work on mistakes. | Problem solving. | Solve problems. | |||
| Stage of motivation and updating of knowledge(determination of the topic of the lesson and the joint goal of the activity). | Provide activities to determine lesson goals. | Offers “Think and Guess” problems, suggests naming the topic of the lesson, and defining the goal. | They are trying to answer, solve problems. Determine the topic of the lesson and purpose. | Personal, cognitive, regulatory | ||
| Operational and content stage |
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| Learning new material. 1) Updating knowledge. 2) Primary assimilation of new knowledge. 3) Initial check of understanding 4) Control of assimilation, discussion of mistakes made and their correction. | Promote students’ activities in independent study of the material. | Offers to organize activities according to the proposed tasks. 1) Suggests recalling the concept of efficiency. 2) Instruction on how to perform the work. Explanation of theoretical material. 3) Offers to complete experimental tasks. 4) suggests drawing conclusions. | Studying new material based on independent laboratory work. 1) They answer. 2) Listen. 3) Perform the proposed experimental tasks. 4) Answer questions. 5) Draw conclusions. They are discussing. | Personal, cognitive, regulatory | ||
| Reflective - evaluative stage. |
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| Reflection. (Summarizing). | An adequate self-esteem of the individual, one’s capabilities and abilities, advantages and limitations is formed. | Prompts you to select an offer. | They answer. | Personal, cognitive, regulatory | ||
| Submitting homework. | Consolidation of the studied material. | Writing on the board. | Write it down in a diary. | Personal | ||
Application.
1. Analysis independent work on the topic "Levers".
Work on mistakes.
Slide number 2.
a) Figure (a) shows a disk mounted on axis O. Forces F and F1 are applied to the disk. Name the shoulders of forces.
b) In figure (b), a person uses a lever to lift a stone weighing 600 N. With what force does a person act on the lever if AB = 1.2 m, BC = 0.5 m.
c) In figure (c), a weight weighing 20 N is placed on a ruler, one end of which rests on the table and the other is held by a dynamometer. Determine the dynamometer readings if length AC = 1 m, BC = 25 cm.
Slide number 3.
a) The figure shows a triangular plate fixed on an axis passing through point O. Forces F and F1 are applied to the plate. Name the shoulders of forces.
b) A person uses a stick to hold 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.
"Think and guess" problems.
1. This is not only a simple mechanism, but also a military alliance.
2. This is the mechanism at the well, and a part of the shirt.
3. In this town 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 can't do without them.
3. Studying new material.
Slide No. 6-7.
An inclined plane is a simple mechanical device used to lift heavy objects to gain strength.
Inclined plane- a simple mechanism in the form of a flat surface installed at an angle other than a straight line to a horizontal surface.
Slide No. 8-10.
The characteristic of the mechanism, which determines what proportion of the useful work is from the total, is called the coefficient of performance - efficiency.
Slide number 11. Invite students to place the inclined plane at different heights. After the experiment and calculations, compare the data obtained.
Action plan for determining the efficiency of an inclined plane:
Measure the weight of the block (P).
Measure the height of the inclined plane (h).
Measure the friction force (Ftr).
Measure the length of the inclined plane (l).
8. Present the results of the work and draw conclusions.
Slide number 12.
Conclusions:
1. Useful work is less than full work.
2. The height of the inclined plane should be less than its length.
3. Efficiency is less than 100%. (At an angle of inclination of 20° to the horizon it is 45%).
4. The efficiency of an 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? Select an offer.
physics teacher, State Educational Institution Lyceum No. 384, Kirovsky District, St. Petersburg
Introduction
The concept of “efficiency” is first introduced in a physics course in the 7th grade. Use of modern educational technologies allows students to increase their learning motivation and efficiency in mastering the material.
When conducting the lesson “Determination of efficiency when lifting a body on an inclined plane,” research technology was used in teaching.
The lesson includes the following stages: updating knowledge, learning new material (doing 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
· Arouse interest in the material being studied
· Motivate students' activities
Goals:
Educational:
· Introduce students to a new physical quantity - the efficiency of a mechanism.
· Confirm through experiments that the useful work done using an inclined plane is less than the work expended.
· Determine the efficiency when lifting an inclined plane.
· Find out what the efficiency depends on when lifting an inclined plane.
· Test the ability to apply acquired knowledge to solve practical and research problems.
· Show the connection between the studied material and life.
Educational:
- Create conditions for the development of students’ personalities in the process of their activities.
- Contribute to the development of practical skills and abilities.
- Develop the ability to put forward a hypothesis and test it.
- To teach to highlight the main thing, to compare, to develop the ability to generalize and systematize the acquired knowledge. 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 health-saving lesson model.
Lesson form: Student research work.
During the classes
· Organizing time.
· Updating knowledge. Warm up.
· Performing laboratory work.
· Physical break.
· Research part of the work.
· Homework.
· Consolidation of the studied material.
1. Organizational moment. Slides 2-3
2. Updating knowledge. Warm up. Slides 4-7
1. What are simple mechanisms?
List what simple mechanisms you know.
Give examples of the use of simple mechanisms.
What are they needed for?
Explain in your own words the meaning of the expression “get 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 simply 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 force.
. What should he do?
(students offer their options)
...then he places two boards on the edge of the body and rolls the barrel along the resulting inclined plane, applying a force significantly 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 lifting them directly.
· Such devices include ramps, escalators, conventional stairs and conveyors.
3. What parameters characterize an inclined plane?
3. Laboratory work No. 10. Slides 12 - 21
“Determination of efficiency when lifting a body along an inclined plane.”
Subject of study: inclined plane.
Compare useful and expended work.
Equipment: Computer, multimedia projector (for teacher)
· Set of weights
· Dynamometer
· Measuring tape (ruler)
Learning new material.
1. Introduce students to a new physical quantity - the efficiency of the mechanism.
Efficiency is a physical quantity equal to the ratio of useful work to expended work, expressed as a percentage.
Efficiency is denoted by the letter "eta"
Efficiency is measured as a percentage.
What work is useful, what work is wasted?
Work spent Spent=F*s
Useful work Auseful = P*h
For example , efficiency = 75%.
This number shows that out of 100% (work expended), 75% of the useful work is done.
Instruction on how to do the job.
Performing laboratory work.
Determine the price of dividing instruments (dynamometer and ruler).
1. Place the board at height h, measure it.
2. Measure the weight of the block P with a dynamometer.
3. Place the block on the board and use a dynamometer to pull it evenly upward along the inclined plane. Measure the force F. Remember how to use a dynamometer correctly.
4. Measure the length of the inclined plane s.
5. Calculate useful and expended work.
6. Calculate the efficiency when lifting a body along an inclined plane.
7. Write down the data in table No. 1.
8. Draw a conclusion.
Registration of work results
Table 1.
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Conclusion: |
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Useful work _______________ than expended.
The efficiency coefficient when lifting a body along an inclined plane is _____%, i.e. this number shows that ___________________________________________________________________.
4. Physical break. Slides 22 - 25
Examples of an inclined plane. Students watch slides with examples of using an inclined plane.
5. Research work. Slides 26 - 30
Problem. What can determine 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 efficiency depend when lifting a body on an inclined plane? from body weight?
Registration of work results
Table 2.
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Conclusion: |
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The efficiency when lifting a body along an inclined plane depends (does not depend) on the height of the inclined plane. The greater (smaller) the height of the inclined plane, the efficiency __________.
The efficiency when lifting a body along an inclined plane depends (does not depend) on the weight of the body. The more (less) the body weight, the efficiency __________.
Discussion of research options.
6. Homework. Slides 31 - 32
Paragraph 60, 61, task 474.
For those who wish to prepare messages.
· Simple mechanisms at my home
· Meat grinder device
· Simple mechanisms in the country
· Simple mechanisms in construction
· Simple mechanisms and the human body
7. Reinforcing the material learned Slides 31 - 34
Work with text
When using _________________ mechanisms, a person commits _______________. Simple mechanisms allow you to win ______________. Moreover, no matter 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, there is ______________________________ friction. Therefore, the amount of _____________________ work is always greater than ____________________. The ratio of _____________________________________________ to ______________________, expressed as a percentage, is called _________________________________________________________________________________________: ______________.
Mini test.
Your efficiency in today's lesson
2. more than 100%
3. less than 100%
Literature
1 A.V. Peryshkin Physics 7th grade. M.: Bustard, 2010
2 G.N. Stepanova Physics 7 workbook part 1. St. Petersburg STP-School, 2003
Technological map of the lesson “Determination of the efficiency of an inclined plane” lesson stage ( regulations, min .)Teacher activities
Student activities
Cognitive
Communicative
Regulatory
Actions taken
Actions taken
Formed methods of activity
Actions taken
Formed methods of activity
Organizational (2 minutes.)
Greets students, notes those who are absent, checks students' readiness for the lesson.
Updating knowledge (8 min.)
Displays slide 2 of the presentation “Efficiency of an Inclined Plane”. Reveals the question chosen by the student and comments on the answer given to it.
Students, one after another, choose a question number, answer it, the rest listen and analyze the given answer.
The ability to consciously construct a speech utterance in oral form and structure knowledge.
If necessary, supplement or correct this answer to the question.
Ability to listen and engage in dialogue accurately
express your thoughts, mastery of monologue and dialogic forms of speech in accordance with the norms of your native language.
Monitor and evaluate their own knowledge and correct it if necessary.
Developing the ability to mobilize strength and energy.
Creating a problematic situation (4 min.)
Creates and invites students to find a way out of a problematic 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 force.
Displays slide 3 (expands scene 5).
Asks a question:Is it only the energy expended by the worker that is spent on lifting the load?
Displays slide 4 (reveals scene 3).
A cognitive goal is identified and formulated: to find a way to lift the body to a height using less force than the body weight.
Choose the most effective way to solve the problem: use 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 efficient the simple mechanism.
Statement and solution of the problem.
Choice of the most effective ways way out of a problem situation depending on specific conditions
Putting forward an assumption about the existence of a physical quantity that characterizes the efficiency of a simple mechanism.
They offer a way out of a problematic situation:
invite assistants, use an inclined plane.
Ability to participate in a collective discussion of a problem
They evaluate the ability to determine the work of overcoming 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 that characterizes the efficiency of an inclined plane.
Staging educational task based on the correlation of what is already known and what is still unknown to students.
Learning new material (8 min.)
Demonstrates lifting a body using an inclined plane, measures body weight and friction force, height and length of the inclined plane.
Displays
slides 5-6.
Gives a description of the efficiency of a simple mechanism.
Compare the weight of the body with the friction force, 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.
Draw a drawing of an inclined plane indicating its length and height, write down the definition and calculation formula for the efficiency of a simple mechanism.
Formation of sign-symbolic UUDs.
A question is asked about the units for measuring 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 identify and realize what has already been learned (calculation of the work of force) and what still needs to be learned (What work is considered useful, what work is expended, how to calculate the efficiency of an inclined plane through the work useful and expended)
Development of knowledge assessment.
Research practical work (17 min.)
Organizes a discussion of the research plan.
Displays
slides 7-11 of the presentation “Efficiency of an inclined plane.”
Provides instruction on safe laboratory work.
Formulates a problematic question:on what parameters does the efficiency of an inclined plane depend?
Distributes equipment sets, IOT, technological maps to groups of students
Assists groups of students in completing work.
Draw up a plan and sequence of actions to determine the efficiency of the inclined plane:
1. Measure the weight of the block (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 an inclined plane depends on the weight of the body being lifted 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 when solving search problems.
Independent formulation of a cognitive task.
Independently put forward a hypothesis about the dependence of the efficiency of an inclined plane on the angle of inclination and the weight of the body being lifted.
Monitor, adjust if necessary and evaluate the actions of the group partner.
Ability to integrate into a peer group and build productive cooperation with peers and adults
Carry out the drawn up action plan to determine the efficiency of the inclined plane:
1. Determine the price of dividing the dynamometer, protractor and measuring tape.
2. Assemble the installation.
2. Measure the weight of the block (P).
3. Measure the height of the inclined plane (h).
4. Calculate useful work 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 using the formula
9. Change the weight of the bar, repeat 1-6.
10. Change the angle of inclination of the plane, repeat 1-6.
11. The results are entered into the table.
Ability to draw up a plan and sequence of actions,
predicting the result.
Reflection (4 min.)
Reminds that the conclusion of the work must be a response to the purpose of the study.
They draw up the results of the work, draw conclusions, and analyze the results obtained.
Conscious construction of speech utterances in written form.
Reflection on methods and conditions of action, control and evaluation of the process and results of activity.
They conclude: during laboratory work, the efficiency of an inclined plane at an angle of inclination of 20 to the horizon turned out to be equal to 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 bodies.
The ability to accurately express your thoughts;
Evaluate the results obtained:
A 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, an error is found in the measurement or calculations.
Ability to evaluate and control the results obtained,
adjust the plan and method of action in case of discrepancy between the standard and the result obtained.
Homework (2 minutes.)
Displays slide 12.
