Experiment in physics. Physics workshop

Oscillations and waves.
Optics.

Tasks for independent work.
Problem 1. Hydrostatic weighing.
Equipment: wooden ruler length 40 cm, plasticine, a piece of chalk, a measuring cup with water, thread, a razor blade, a tripod with a holder.
Exercise.
Measure

density of plasticine;
chalk density;
a mass of wooden ruler.

Notes:

It is advisable not to wet the piece of chalk - it may fall apart.
The density of water is considered equal to 1000 kg/m3

Problem 2. Specific heat of dissolution of hyposulfite.
When hyposulfite is dissolved in water, the temperature of the solution decreases greatly.
Measure the specific heat of solution of a given substance.
The specific heat of solution is the amount of heat required to dissolve a unit mass of a substance.
The specific heat capacity of water is 4200 J/(kg × K), the density of water is 1000 kg/m 3.
Equipment: calorimeter; beaker or measuring cup; scales with weights; thermometer; crystalline hyposulfite; warm water.

Problem 3. Mathematical pendulum and acceleration free fall .

Equipment: tripod with foot, stopwatch, piece of plasticine, ruler, thread.
Exercise: Measure the acceleration of gravity using a mathematical pendulum.

Problem 4. Refractive index of the lens material.
Exercise: Measure the refractive index of the glass the lens is made from.

Equipment: biconvex lens on a stand, light source (light bulb on a stand with a current source and connecting wires), screen on a stand, caliper, ruler.

Problem 5. “Rod vibrations”

Equipment: tripod with foot, stopwatch, knitting needle, eraser, needle, ruler, plastic stopper plastic bottle.

Investigate the dependence of the oscillation period of the resulting physical pendulum on the length of the upper part of the spoke. Plot a graph of the resulting relationship. Check the feasibility of formula (1) in your case.
Determine, as accurately as possible, the minimum period of oscillation of the resulting pendulum.
Determine the value of the acceleration due to gravity.

Task 6. Determine the resistance of the resistor as accurately as possible.
Equipment: current source, resistor with known resistance, resistor with unknown resistance, glass (glass, 100 ml), thermometer, watch (you can use your wristwatch), graph paper, piece of foam plastic.

Problem 7. Determine the coefficient of friction of the block on the table.
Equipment: block, ruler, tripod, thread, weight of known mass.

Problem 8. Determine the weight of a flat figure.
Equipment: flat figure, ruler, weight.

Task 9. Investigate the dependence of the speed of the stream flowing out of the vessel on the height of the water level in this vessel.
Equipment: tripod with coupling and foot, glass burette with scale and rubber tube; spring clip; screw clamp; stopwatch; funnel; cuvette; glass of water; sheet of graph paper.

Problem 10. Determine the temperature of water at which its density is maximum.
Equipment: glass of water, at temperature t = 0 °C; metal stand; thermometer; spoon; watch; small glass.

Problem 11. Determine the breaking force T threads, mg< T .
Equipment: a strip whose length 50 cm; thread or thin wire; ruler; load of known mass; tripod.

Problem 12. Determine the coefficient of friction of a metal cylinder, the mass of which is known, on the table surface.
Equipment: two metal cylinders of approximately the same mass (the mass of one of them is known ( m = 0.4 - 0.6 kg)); length ruler 40 - 50 cm; Bakushinsky dynamometer.

Task 13. Explore the contents of a mechanical “black box”. Determine the characteristics of a solid body enclosed in a “box”.
Equipment: dynamometer, ruler, graph paper, “black box” - a closed jar, partially filled with water, in which there is a solid body with a rigid wire attached to it. The wire comes out of the jar through a small hole in the lid.

Problem 14. Determine the density and specific heat capacity of an unknown metal.
Equipment: calorimeter, plastic beaker, bath for developing photographs, measuring cylinder (beaker), thermometer, threads, 2 cylinders of unknown metal, vessel with hot ( t g = 60° –70°) and cold ( t x = 10° – 15°) water. Specific heat capacity of water c in = 4200 J/(kg × K).

Problem 15. Determine the Young's modulus of steel wire.
Equipment: tripod with two legs for attaching equipment; two steel rods; steel wire (diameter 0.26 mm); ruler; dynamometer; plasticine; pin.
Note. The wire stiffness coefficient depends on the Young's modulus and the geometric dimensions of the wire as follows k = ES/l, Where l– wire length, a S– its cross-sectional area.

Task 16. Determine the concentration of table salt in the aqueous solution given to you.
Equipment: glass jar volume 0.5 l; a vessel with an aqueous solution of table salt of unknown concentration; source alternating current with adjustable voltage; ammeter; voltmeter; two electrodes; connecting wires; key; a set of 8 weighed amounts of table salt; graph paper; container with fresh water.

Problem 17. Determine the resistance of a millivoltmeter and milliammeter for two measurement ranges.
Equipment: millivoltmeter ( 50/250 mV), milliammeter ( 5/50 mA), two connecting wires, copper and zinc plates, pickled cucumber.

Problem 18. Determine the density of the body.
Equipment: body irregular shape, metal rod, ruler, tripod, vessel with water, thread.

Task 19. Determine the resistances of resistors R 1, ..., R 7, ammeter and voltmeter.
Equipment: battery, voltmeter, ammeter, connecting wires, switch, resistors: R 1 – R 7.

Problem 20. Determine the spring stiffness coefficient.
Equipment: spring, ruler, sheet of graph paper, block, mass 100 g.
Attention! Do not suspend a load from a spring, as this will exceed the elastic deformation limit of the spring.

Problem 21. Determine the coefficient of sliding friction of a match head on the rough surface of a matchbox.
Equipment: box of matches, dynamometer, weight, sheet of paper, ruler, thread.

Problem 22. The fiber optic connector part is a glass cylinder (refractive index n= 1.51), in which there are two round cylindrical channels. The ends of the part are sealed. Determine the distance between channels.
Equipment: connector part, graph paper, magnifying glass.

Problem 23. “Black Vessel”. A body is lowered into a “black vessel” of water on a string. Find the density of the body ρ m, its height l the water level in the vessel with the immersed body ( h) and when the body is outside the liquid ( h o).
Equipment. “Black vessel”, dynamometer, graph paper, ruler.
Density of water 1000 kg/m 3. Vessel depth H = 32 cm.

Problem 24. Friction. Determine the sliding friction coefficients of wooden and plastic rulers on the table surface.
Equipment. Tripod with foot, plumb line, wooden ruler, plastic ruler, table.

Problem 25. Wind-up toy. Determine the energy stored in the spring of a wind-up toy (car) at a fixed “winding” (number of turns of the key).
Equipment: a wind-up toy of known mass, a ruler, a tripod with a foot and a coupling, an inclined plane.
Note. Wind up the toy so that its mileage does not exceed the length of the table.

Problem 26. Determining the density of bodies. Determine the density of the weight (rubber plug) and the lever (wooden strip) using the proposed equipment.
Equipment: load of known mass (marked plug); lever (wooden slats); cylindrical glass ( 200 - 250 ml); a thread ( 1m); wooden ruler, vessel with water.

Problem 27. Studying the motion of the ball.
Raise the ball to a certain height above the table surface. Let's release him and watch his movement. If the collisions were absolutely elastic (sometimes they say elastic), then the ball would jump to the same height all the time. In reality, the height of the jumps is constantly decreasing. The time interval between successive jumps also decreases, which is clearly noticeable by ear. After some time, the bouncing stops and the ball remains on the table.
1 task – theoretical.
1.1. Determine the fraction of energy lost (energy loss coefficient) after the first, second, third rebound.
1.2. Obtain the dependence of time on the number of bounces.

Task 2 – experimental.
2.1. Using the direct method, using a ruler, determine the energy loss coefficient after the first, second, third impact.
It is possible to determine the energy loss coefficient using a method based on measuring the total time of motion of the ball from the moment it is thrown from a height H until the moment it stops bouncing. To do this, you have to establish the relationship between the total movement time and the energy loss coefficient.
2.2. Determine the energy loss coefficient using a method based on measuring the total time of motion of the ball.
3. Errors.
3.1. Compare the measurement errors of the energy loss coefficient in paragraphs 2.1 and 2.2.

Problem 28. Stable test tube.

Find the mass of the test tube given to you and its outer and inner diameters.
Calculate theoretically at what minimum height h min and maximum height h max of water poured into a test tube it will float stably in a vertical position, and find the numerical values using the results of the first point.
Determine h min and h max experimentally and compare with the results of step 2.

Equipment. A test tube of unknown mass with a scale pasted on, a vessel with water, a glass, a sheet of graph paper, a thread.
Note. It is prohibited to peel off the scale from the test tube!

Problem 29. Angle between mirrors. Determine the dihedral angle between mirrors with the greatest accuracy.
Equipment. A system of two mirrors, a measuring tape, 3 pins, a sheet of cardboard.

Problem 30. Ball segment.
A spherical segment is a body bounded by a spherical surface and a plane. Using this equipment, construct a graph of volume dependence V spherical segment of unit radius r = 1 from its height h.
Note. The formula for the volume of a spherical segment is not assumed to be known. Take the density of water equal to 1.0 g/cm3.
Equipment. A glass of water, a tennis ball of known mass m with a puncture, a syringe with a needle, a sheet of graph paper, tape, scissors.

Problem 31. Snow with water.
Determine the mass fraction of snow in the snow-water mixture at the time of delivery.
Equipment. A mixture of snow and ice, a thermometer, a watch.
Note. Specific heat water c = 4200 J/(kg × °C), specific heat of melting of ice λ = 335 kJ/kg.

Problem 32. Adjustable “black box”.
In a “black box” with 3 outputs, an electrical circuit is assembled, consisting of several resistors with a constant resistance and one variable resistor. The resistance of the variable resistor can be changed from zero to a certain maximum value R o using an adjustment knob brought out.
Using an ohmmeter, examine the black box circuit and, assuming that the number of resistors in it is minimal,

draw a diagram of an electrical circuit contained in a “black box”;
calculate the resistance of constant resistors and the value of R o;
evaluate the accuracy of your calculated resistance values.

Problem 33. Measuring electrical resistance.
Determine the resistance of the voltmeter, battery and resistor. It is known that a real battery can be represented as an ideal one, connected in series with a certain resistor, and a real voltmeter can be represented as an ideal one, with a resistor connected in parallel.
Equipment. Battery, voltmeter, resistor with unknown resistance, resistor with known resistance.

Problem 34. Weighing ultra-light loads.
Using the proposed equipment, determine the mass m of a piece of foil.
Equipment. A jar of water, a piece of foam plastic, a set of nails, wooden toothpicks, a ruler with millimeter divisions or graph paper, a sharpened pencil, foil, napkins.

Problem 35. CVC CHA.
Determine the current-voltage characteristic (CVC) of the “black box” ( CHY). Describe the technique for measuring the current-voltage characteristic and plot its graph. Assess the errors.
Equipment. FC limiting the resistor with a known resistance R, multimeter in voltmeter mode, adjustable current source, connecting wires, graph paper.
Attention. Connect CHY to the current source bypassing the limiting resistor is strictly prohibited.

Problem 36. Soft spring.

Experimentally investigate the dependence of the elongation of a soft spring under the action of its own weight on the number of turns of the spring. Give theoretical explanation found dependency.
Determine the elasticity coefficient and mass of the spring.
Investigate the dependence of the period of oscillation of a spring on its number of turns.

Equipment: soft spring, tripod with foot, tape measure, clock with second hand, plasticine ball m = 10 g, graph paper.

Problem 37. Wire density.
Determine the density of the wire. Breaking the wire is not allowed.
Equipment: piece of wire, graph paper, thread, water, vessel.
Note. Density of water 1000 kg/m 3.

Problem 38. Friction coefficient.
Determine the coefficient of sliding friction of the bobbin material on wood. The bobbin axis must be horizontal.
Equipment: bobbin, thread length 0.5 m, wooden ruler fixed at an angle in a tripod, graph paper.
Note. During work, it is prohibited to change the position of the ruler.

Problem 39. The share of mechanical energy.
Determine the fraction of mechanical energy lost by a ball when falling without an initial speed from a height 1m.
Equipment: tennis ball, ruler length 1.5 m, sheet of white paper A4, sheet of copy paper, glass plate, ruler; brick.
Note: for small deformations of the ball, Hooke’s law can (but not necessarily) be considered valid.

Problem 40. Vessel with water “black box”.
The “black box” is a vessel with water into which a thread is lowered, on which two weights are attached at some distance from each other. Find the masses of the loads and their densities. Assess the size of the loads, the distance between them and the water level in the vessel.
Equipment: “black box”, dynamometer, graph paper.

Problem 41. Optical “black box”.
An optical “black box” consists of two lenses, one of which is converging and the other is diverging. Determine their focal lengths.
Equipment: tube with two lenses (optical “black” box), light bulb, current source, ruler, screen with a sheet of graph paper, sheet of graph paper.
Note. The use of light from a remote source is allowed. Bringing the light bulb close to the lenses (that is, closer than the stands allow) is not allowed.

The importance and types of independent experiment of students in physics. When teaching physics in high school, experimental skills are developed by performing independent laboratory work.

Teaching physics cannot be presented only in the form of theoretical classes, even if students are shown physical demonstration experiments in class. To all types of sensory perception, it is imperative to add “work with your hands” in classes. This is achieved when students perform a laboratory physical experiment, when they themselves assemble installations and carry out measurements physical quantities, perform experiments. Laboratory classes arouse very great interest among students, which is quite natural, since in this case the student learns about the world around him based on own experience and your own feelings.

The importance of laboratory classes in physics lies in the fact that students develop ideas about the role and place of experiment in knowledge. When performing experiments, students develop experimental skills, which include both intellectual and practical skills. The first group includes the skills to: determine the purpose of the experiment, put forward hypotheses, select instruments, plan an experiment, calculate errors, analyze the results, draw up a report on the work done. The second group includes the skills to assemble an experimental setup, observe, measure, and experiment.

In addition, the value laboratory experiment is that when performing it, students develop such important personal qualities as accuracy in working with instruments; maintaining cleanliness and order in the workplace, in the notes made during the experiment, organization, persistence in obtaining results. They develop a certain culture of mental and physical labor.

In the practice of teaching physics at school, three types of laboratory classes have developed:

Frontal laboratory work in physics;

Physical workshop;

Home experimental work in physics.

Front laboratory work- this is a type of practical work when all students in a class simultaneously perform the same type of experiment using the same equipment. Front-end laboratory work is most often performed by a group of students consisting of two people; sometimes it is possible to organize individual work. Accordingly, the office should have 15-20 sets of instruments for frontal laboratory work. Total There will be about a thousand such devices. The names of frontal laboratory work are given in the curriculum. There are quite a lot of them, they are provided for almost every topic of the physics course. Before carrying out the work, the teacher identifies the students’ readiness to consciously carry out the work, determines its purpose with them, discusses the progress of the work, the rules for working with instruments, and methods for calculating measurement errors. Front-end laboratory work is not very complex in content, is closely related chronologically to the material being studied and, as a rule, is designed for one lesson. Descriptions of laboratory work can be found in school physics textbooks.

Physics workshop carried out with the aim of repeating, deepening, expanding and generalizing the knowledge gained from different topics physics course; development and improvement of students' experimental skills through the use of more complex equipment, more complex experiments; formation of their independence in solving problems related to the experiment. Physics workshop is not related in time to the material being studied; it is usually held at the end school year, sometimes at the end of the first and second half of the year and includes a series of experiments on a particular topic. Students perform physical practical work in a group of 2-4 people at various equipment; During the next classes there is a change of work, which is done according to a specially designed schedule. When drawing up a schedule, take into account the number of students in the class, the number of workshops, and the availability of equipment. Two teaching hours are allocated for each physics workshop, which requires the introduction of double physics lessons into the schedule. This presents difficulties. For this reason and due to the lack of necessary equipment, one-hour physical workshops are practiced. It should be noted that two-hour work is preferable, since the work of the workshop is more complex than frontal laboratory work; complex equipment, and the share of independent participation of students is much greater than in the case of frontal laboratory work. Physical workshops are provided mainly by the programs of grades 9-11. In each class, approximately 10 hours of instructional time are allocated for the workshop. For each work, the teacher must draw up instructions, which should contain: title, purpose, list of instruments and equipment, brief theory, description of devices unknown to students, plan for completing the work. After completing the work, students must submit a report, which must contain: the title of the work, the purpose of the work, a list of instruments, a diagram or drawing of the installation, a plan for performing the work, a table of results, formulas by which the values of quantities were calculated, calculations of measurement errors, conclusions. When assessing students’ work in a workshop, one should take into account their preparation for work, work report, level of skills, understanding of theoretical material, methods used experimental research.

Home experimental work. Home laboratory work is the simplest independent experiment that is carried out by students at home, outside of school, without direct supervision by the teacher over the progress of the work.

The main objectives of experimental work of this type are:

Formation of the ability to observe physical phenomena in nature and in everyday life;

Formation of the ability to carry out measurements using measuring instruments used in everyday life;

Formation of interest in experiments and in the study of physics;

Formation of independence and activity.

Home laboratory work can be classified depending on the equipment used to perform it:

Works that use household items and available materials (measuring cup, tape measure, household scales, etc.);

Works in which homemade instruments are used (lever scales, electroscope, etc.);

Work performed on devices produced by industry.

Classification taken from.

In his book S.F. Pokrovsky showed that home experiments and observations in physics conducted by the students themselves: 1) enable our school to expand the area of connection between theory and practice; 2) develop students’ interest in physics and technology; 3) awaken creative thought and develop the ability to invent; 4) teach students to be independent research work; 5) develop valuable qualities in them: observation, attention, perseverance and accuracy; 6) supplement classroom laboratory work with material that cannot be completed in class (a series of long-term observations, observation natural phenomena etc.), and 7) accustom students to conscious, purposeful work.

Home experiments and observations in physics have their own characteristic features, being an extremely useful addition to classroom and school practical work in general.

It has long been recommended that students have a home laboratory. it included, first of all, rulers, a beaker, a funnel, scales, weights, a dynamometer, a tribometer, a magnet, a watch with a second hand, iron filings, tubes, wires, a battery, and a light bulb. However, despite the fact that the set includes very simple devices, this proposal has not gained popularity.

To organize home experimental work for students, you can use the so-called mini-laboratory proposed by teacher-methodologist E.S. Obedkov, which includes many household items (penicillin bottles, rubber bands, pipettes, rulers, etc.) that is available to almost every schoolchild. E.S. Obyedkov developed a very large number of interesting and useful experiments with this equipment.

It also became possible to use a computer to conduct a model experiment at home. It is clear that the corresponding tasks can only be offered to those students who have a computer and software and pedagogical tools at home.

In order for students to want to learn, the learning process must be interesting for them. What is interesting to students? To get an answer to this question, let us turn to excerpts from the article by I.V. Litovko, MOS(P)Sh No. 1, Svobodny “Home experimental tasks as an element of student creativity”, published on the Internet. This is what I.V. writes. Litovko:

“One of the most important tasks of the school is to teach students to learn, to strengthen their ability for self-development in the educational process, for which it is necessary to form in schoolchildren the corresponding stable desires, interests, and skills. An important role in this is played by experimental tasks in physics, which in their content represent short-term observations, measurements and experiments that are closely related to the topic of the lesson. The more observations of physical phenomena and experiments a student makes, the better he will understand the material being studied.

To study students’ motivation, they were asked the following questions and the results were obtained:

What do you like about studying physics? ?

a) problem solving -19%;

b) demonstration of experiments -21%;

In the first chapter of the thesis, we discussed theoretical aspects problems of using electronic textbooks in the process of teaching physics at senior level secondary school. In the course of a theoretical analysis of the problem, we identified the principles and types of electronic textbooks, identified and theoretically substantiated the pedagogical conditions for the use of information technologies in the process of teaching physics at the senior level of secondary schools.

In the second chapter of the thesis, we formulate the purpose, objectives and principles of organizing experimental work. This chapter discusses the methodology for implementing the pedagogical conditions we have identified for the use of electronic textbooks in the process of teaching physics at the senior level of a comprehensive school; the final paragraph provides an interpretation and evaluation of the results obtained during the experimental work.

Purpose, objectives, principles and methods of organizing experimental work

In the introductory part of the work, a hypothesis was put forward that contained the main conditions that require testing in practice. In order to test and prove the proposals put forward in the hypothesis, we carried out experimental work.

Experiment at the Philosophical encyclopedic dictionary» is defined as a systematically conducted observation; systematic isolation, combination and variation of conditions in order to study the phenomena that depend on them. Under these conditions, a person creates the possibility of observations, on the basis of which his knowledge of the patterns in the observed phenomenon is formed. Observations, conditions and knowledge about patterns are the most significant, in our opinion, features that characterize this definition.

In the Psychology dictionary, the concept of experiment is considered as one of the main (along with observation) methods scientific knowledge at all, psychological research in particular. It differs from observation by active intervention in the situation on the part of the researcher, carrying out systematic manipulation of one or more variables (factors) and recording accompanying changes in the behavior of the studied object. A correctly set up experiment allows you to test hypotheses about cause-and-effect relationships and is not limited to establishing a connection (correlation) between variables. The most significant features, as experience shows, here are: the activity of the researcher, characteristic of the exploratory and formative types of experiment, as well as testing the hypothesis.

Highlighting the essential features of the above definitions, as rightly written by A.Ya. Nain and Z.M. Umetbaev, one can construct and use the following concept: an experiment is research activities, designed to test a hypothesis, deployed in natural or artificially created controlled and controlled conditions. The result of this, as a rule, is new knowledge, including the identification of significant factors influencing efficiency pedagogical activity. Organization of an experiment is impossible without identifying criteria. And it is their presence that makes it possible to distinguish experimental activity from any other. These criteria, according to E.B. Kainova, there may be the presence of: the purpose of the experiment; hypotheses; scientific language descriptions; specially created experimental conditions; diagnostic methods; ways of influencing the subject of experimentation; new pedagogical knowledge.

Based on their goals, they distinguish between ascertaining, formative and evaluative experiments. The purpose of the ascertaining experiment is to measure the current level of development. In this case, we receive primary material for research and organization of a formative experiment. This is extremely important for the organization of any survey.

A formative (transforming, training) experiment aims not at a simple statement of the level of formation of this or that activity, the development of certain skills of the subjects, but their active formation. Here it is necessary to create a special experimental situation. The results of an experimental study often do not represent an identified pattern, a stable dependence, but a series of more or less fully recorded empirical facts. This data is often descriptive in nature, representing only more specific material that narrows the further scope of the search. The results of an experiment in pedagogy and psychology should often be considered as intermediate material and the initial basis for further research work.

Evaluation experiment (controlling) - with its help, after a certain period of time after the formative experiment, the level of knowledge and skills of the subjects is determined based on the materials of the formative experiment.

The purpose of the experimental work is to test the identified pedagogical conditions for the use of electronic textbooks in the process of teaching physics at the senior level of a secondary school and determine their effectiveness.

The main objectives of the experimental work were: selection of experimental sites for the pedagogical experiment; defining criteria for selecting experimental groups; development of tools and determination of methods for pedagogical diagnostics of selected groups; development of pedagogical criteria for identifying and correlating the levels of learning of students in control and experimental classes.

The experimental work was carried out in three stages, including: a diagnostic stage (carried out in the form of a confirmatory experiment); content stage (organized in the form of a formative experiment) and analytical (conducted in the form of a control experiment). Principles of carrying out experimental work.

The principle of comprehensiveness of scientific and methodological organization of experimental work. The principle requires ensuring a high level of professionalism of the experimental teacher himself. The effectiveness of the implementation of information technologies in teaching schoolchildren is influenced by many factors, and, undoubtedly, its basic condition is the correspondence of the content of training to the capabilities of schoolchildren. But even in this case, problems arise in overcoming intellectual and physical barriers, and therefore, when using methods of emotional and intellectual stimulation of students’ cognitive activity, we provided methodological counseling that meets the following requirements:

a) problem-search material was presented using personalized explanatory methods and instructions to facilitate students’ assimilation of educational material;

b) various techniques and ways of mastering the content of the material being studied were proposed;

c) individual teachers had the opportunity to freely choose techniques and schemes for solving computerized problems, and work according to their original pedagogical techniques.

The principle of humanizing the content of experimental work. This is the idea of priority human values over technocratic, production, economic, administrative, etc. The principle of humanization was implemented by observing following rules pedagogical activity: a) the pedagogical process and educational relations in it are built on full recognition of the rights and freedoms of the student and respect for him;

b) know and during the pedagogical process rely on the positive qualities of the student;

c) constantly carry out humanistic education of teachers in accordance with the Declaration of the Rights of the Child;

d) ensure the attractiveness and aesthetics of the pedagogical space and the comfort of the educational relations of all its participants.

Thus, the principle of humanization, as I.A. Kolesnikova and E.V. Titova believe, provides schoolchildren with a certain social protection in an educational institution.

The principle of democratization of experimental work is the idea of providing participants in the pedagogical process with certain freedoms for self-development, self-regulation, and self-determination. The principle of democratization in the process of using information technologies for teaching schoolchildren is implemented through compliance with the following rules:

a) create a pedagogical process open to public control and influence;

b) create legal support for students’ activities that will help protect them from adverse environmental influences;

c) ensure mutual respect, tact and patience in the interaction between teachers and students.

The implementation of this principle helps to expand the capabilities of students and teachers in determining the content of education, choosing the technology for using information technology in the learning process.

The principle of cultural conformity of experimental work is the idea of maximum use in upbringing, education and training of the environment in which and for the development of which the educational institution was created - the culture of the region, people, nation, society, country. The principle is implemented based on compliance with the following rules:

a) understanding of cultural and historical value by the teaching community at school;

b) maximum use of family and regional material and spiritual culture;

c) ensuring the unity of national, international, interethnic and intersocial principles in the upbringing, education, and training of schoolchildren;

d) the formation of creative abilities and attitudes of teachers and students to consume and create new ones cultural values.

The principle of a holistic study of pedagogical phenomena in experimental work, which involves: the use of systemic and integrative - developmental approaches; a clear definition of the place of the phenomenon being studied in the holistic pedagogical process; disclosure of the driving forces and phenomena of the objects being studied.

We were guided by this principle when modeling the process of using educational information technologies.

The principle of objectivity, which involves: checking each fact using several methods; recording all manifestations of changes in the object under study; comparison of the data from your study with data from other similar studies.

The principle was actively used in the process of conducting the ascertaining and formative stages of the experiment, when using an electronic process in educational process, as well as when analyzing the results obtained.

The principle of adaptation, which requires taking into account the personal characteristics and cognitive abilities of students in the process of using information technology, was used when conducting a formative experiment. The principle of activity, which assumes that correction of the personal semantic field and behavioral strategy can only be carried out during the active and intensive work of each participant.

The principle of experimentation, aimed at actively searching for new behavioral strategies by participants in classes. This principle is important as an impetus for the development of creativity and initiative of the individual, as well as as a model of behavior in real life student

It is possible to talk about learning technology using electronic textbooks only if: it satisfies the basic principles of pedagogical technology (preliminary design, reproducibility, goal setting, integrity); it solves problems that were not previously theoretically and/or practically solved in didactics; The computer is the means of preparing and transmitting information to the learner.

In this regard, we present the basic principles of the systemic implementation of computers in educational process, which were widely used in our experimental work.

The principle of new tasks. Its essence is not to transfer traditionally established methods and techniques to the computer, but to rebuild them in accordance with the new capabilities that computers provide. In practice, this means that when analyzing the learning process, losses are identified that occur from shortcomings in its organization (insufficient analysis of the content of education, poor knowledge of the real educational capabilities of schoolchildren, etc.). In accordance with the result of the analysis, a list of tasks is outlined that, due to various objective reasons (large volume, enormous time expenditure, etc.) are currently not being solved or are being solved incompletely, but which can be completely solved with the help of a computer. These tasks should be aimed at the completeness, timeliness and at least approximate optimality of the decisions made.

The principle of a systems approach. This means that the introduction of computers must be based on system analysis learning process. That is, the goals and criteria for the functioning of the learning process must be determined, structuring must be carried out, revealing the whole range of issues that need to be resolved in order for the designed system the best way met the established goals and criteria.

Principles of the most reasonable typification of design solutions. This means that when developing software, the contractor must strive to ensure that the solutions he offers are suitable for the widest possible range of customers, not only in terms of the types of computers used, but also various types of educational institutions.

In conclusion of this paragraph, we note that the use of the above methods with other methods and principles of organizing experimental work made it possible to determine the attitude towards the problem of using electronic textbooks in the learning process, and to outline specific ways to effectively solve the problem.

Following the logic of theoretical research, we formed two groups - control and experimental. In the experimental group, the effectiveness of the selected pedagogical conditions was tested; in the control group, the organization of the learning process was traditional.

Educational features of the implementation of pedagogical conditions for the use of electronic textbooks in the process of teaching physics at senior levels are presented in paragraph 2.2.

The results of the work done are reflected in paragraph 2.3.

1. Explanatory note.

Physics teaching in high school is based on the physics course in primary school, subject to differentiation. The content of education should facilitate the implementation of a multi-level approach. Lyceum No. 44 aims to optimally develop the creative abilities of students with a special interest in the field of physics; this level of teaching is carried out in classes with in-depth study of physics.

The objects of study in a physics course at a level accessible to students, along with fundamental physical concepts and laws, should be experiment as a method of cognition, a method for constructing models and a method for their theoretical analysis. Lyceum graduates must understand what the essence of models is natural objects(processes) and hypotheses, how theoretical conclusions are made, how to experimentally test models, hypotheses and theoretical conclusions.

At the lyceum, the number of hours in physics in advanced classes does not correspond to the new status of the physics and mathematics lyceum: in 9 classes - 2 hours. In this regard, it is proposed that technology lessons in grade 9 (1 hour per week, divided into two groups) be replaced with practical experimental physics in addition to the main lessons on the clock grid.

The purpose of the course is to provide students with the opportunity to satisfy their individual interest in studying practical applications of physics in the process of cognitive and creative activity while conducting independent experiments and research.

The main objective of the course is to help students make an informed choice of a profile for further education.

The program consists of the following parts: a) errors; b) laboratory work; c) experimental work; d) experimental tasks; d) testing.

In elective classes, schoolchildren will get to know in practice those types of activities that are leading in many engineering and technical professions related to the practical application of physics. The experience of independently performing first simple physical experiments, then tasks of research and design type will allow you to either verify the correctness of the preliminary choice, or change your choice and try yourself in some other direction.

At the same time, theoretical classes are advisable only at the first stage when forming a group and determining the interests and abilities of students.

The main forms of classes should be practical work by students in a physics laboratory and performing simple experimental tasks at home.

In practical classes when performing laboratory work, students will be able to acquire the skills of planning a physical experiment in accordance with the task, learn to choose a rational measurement method, perform an experiment and process its results. Completing practical and experimental tasks will allow you to apply the acquired skills in a non-standard environment and become competent in many practical issues.

All types of practical tasks are designed to use standard equipment in a physics classroom and can be performed in the form of laboratory work or as experimental tasks of your choice.

The elective course is aimed at instilling in schoolchildren self-confidence and the ability to use a variety of devices and household appliances in everyday life, as well as developing interest in carefully examining familiar phenomena and objects. The desire to understand, to understand the essence of phenomena, the structure of things that serve a person throughout his life, will inevitably require additional knowledge, push him to self-education, force him to observe, think, read, and invent.

Methods for measuring physical quantities (2 hours).

Basic and derived physical quantities and their measurements. Units and standards of quantities. Absolute and relative errors of direct measurements. Measuring instruments, tools, measures. Instrumental and reference errors. Instrument accuracy classes. Limits of systematic errors and methods for their assessment. Random measurement errors and estimation of their limits.

Stages of planning and performing an experiment. Precautions when conducting the experiment. Taking into account the influence of measuring instruments on the process under study. Selection of measurement method and measuring instruments.

Methods for monitoring measurement results. Recording measurement results. Tables and graphs. Processing of measurement results. Discussion and presentation of the results obtained.

Laboratory work (16 hours).

Calculation of measurement errors of physical quantities.
Study of uniformly accelerated motion.
Determination of the acceleration of a body during uniformly accelerated motion.
Measuring body weight.
Study of Newton's second law.
Determination of spring stiffness.
Determination of sliding friction coefficient.
Study of the motion of a body thrown horizontally.
Study of the motion of a body in a circle under the influence of several forces.
Clarification of the conditions of equilibrium of bodies under the influence of several forces.
Determination of the center of gravity of a flat plate.
Study of the law of conservation of momentum.
Measuring the efficiency of an inclined plane.
Comparison of the work done with the change in body energy.
Study of the law of conservation of energy.
Measuring the acceleration of gravity using a pendulum.

Experimental work (4 hours).

Calculation of average and instantaneous speed.
Measuring speed at the bottom of an inclined plane.
Calculation and measurement of the speed of a ball rolling down an inclined chute.
Study of oscillations of a spring pendulum.

Experimental tasks (10 hours).

Solving experimental problems for grade 7 (2 hours).
Solving experimental problems for grade 8 (2 hours).
Solving experimental problems of grade 9 (2 hours).
Solving experimental problems using a computer (4 hours).

Tested task (1 hour).

General lesson (1 hour).

3.Certification of students.

The credit form for assessing student achievements best corresponds to the characteristics of elective classes. It is advisable to give credit for laboratory work performed based on the submitted written report, which briefly describes the experimental conditions. The measurement results are presented in a systematic manner and conclusions are drawn.

Based on the results of completing creative experimental tasks, in addition to written reports, it is useful to practice reports in a general group lesson with a demonstration of completed experiments and manufactured devices. To conduct general results of the entire group’s classes, it is possible to hold a competition of creative works. At this competition, students will not only be able to demonstrate the experimental installation in action, but also talk about its originality and capabilities. Here it is especially important to format your report with graphs, tables, and briefly and emotionally talk about the most important things. In this case, it becomes possible to see and evaluate your work and yourself against the background of other interesting works and equally passionate people.

The student’s final grade for the entire elective course can be assessed, for example, according to the following criteria: completion of at least half of the laboratory work; performing at least one experimental task of a research or design type; Active participation in preparing and conducting seminars, discussions, competitions.

The proposed criteria for assessing student achievement can only serve as a guide, but are not mandatory. Based on his experience, the teacher can set other criteria.

4. Literature:

Demonstration experiment in physics in high school./Ed. A. A. Pokrov
sky. Part 1. - M.: Education, 1978.
Methods of teaching physics in grades 7-11 of secondary school./Edited by V.P.
Orekhova and A.V. Usova. - M.: Education, 1999.
Martynov I.M., Khozyainova E.N. Didactic material on physics. 9th grade. - M.:
Enlightenment, 1995.
V.A.Burov, A.I.Ivanov, V.I.Sviridov. Frontal experimental tasks on
Physics. 9th grade. – M: Prosveshchenie. 1988.
Rymkevich A.P., Rymkevich P.A. Collection of physics problems for grades 9 – 11. – M.: About
glow, 2000.
Stepanova G.N. Collection of problems in physics: For grades 9-11 of general education
decisions. - M.: Education, 1998.
Gorodetsky D.N., Penkov I.A. Test work in physics. – Minsk “Highest”
school”, 1987
V.A. Burov, S.F. Kabanov, V.I. Sviridov. “Front-line experimental tasks on
physics.” – M: Enlightenment.1988
Kikoin I.K., Kikoin A.K. Physics: Textbook for 10 grades - M.: Education, 2003

T THEMATIC PLANNING FOR PHYSICS IN 9TH CLASS

Elective course: “Practical and experimental physics”

(in-depth study - 34 hours)

Stage – third

Level – advanced

№	Lesson type	Watch	Lesson content	D/z
1	Lecture	1h	Safety precautions.	Abstract
2	Lecture	1h	Errors in measurements of physical quantities.	Abstract
3	Laboratory work No. 1	1h	Calculation of measurement errors of physical quantities	Finish calculations
4		1h		tasks
5	Experimental work	1h	Calculation of average and instantaneous speed	Finish calculations
6	Laboratory work No. 2	1h	Study of uniformly accelerated motion	Finish calculations
7	Laboratory work No. 3.	1 hour	Determination of the acceleration of a body during uniformly accelerated motion.	Finish calculations
8	Experimental work	1 hour	Measuring speed at the bottom of an inclined plane.	Finish calculations
9	Laboratory work No. 4	1h	Measuring body mass	Finish calculations
10	Laboratory work No. 5	1h	Studying Newton's Second Law	Finish calculations
11	Laboratory work No. 6	1 hour	Determination of spring stiffness.	Finish calculations
12	Laboratory work No. 7	1 hour	Determination of sliding friction coefficient.	Finish calculations
13	Laboratory work No. 8	1 hour	Study of the motion of a body thrown horizontally.	Finish calculations
14	Laboratory work No. 9	1 hour	Study of the motion of a body in a circle under the influence of several forces.”	Finish calculations
15	Solving experimental problems	1h	Solving experimental problems for 7th grade	tasks
16	Laboratory work No. 10	1 hour	Clarification of the conditions of equilibrium of bodies under the influence of several forces.	Finish calculations
17	Laboratory work No. 11	1 hour	Determination of the center of gravity of a flat plate.	Finish calculations
18	Solving experimental problems	1h		tasks
19	Solving experimental problems	1h	Solving experimental problems for 8th grade	tasks
20	Laboratory work No. 12	1h	Study of the law of conservation of momentum	Finish calculations
21	Laboratory work No. 13	1h	Inclined Plane Efficiency Measurement	Finish calculations
22	Laboratory work No. 14	1 hour	Comparison of the work done with the change in body energy”	Finish calculations
23	Laboratory work No. 15	1h	Studying the Law of Conservation of Energy	Finish calculations
24	Experimental work	1h	Calculation and measurement of the speed of a ball rolling down an inclined chute	Finish calculations
25	Solving experimental problems	1h		Tasks
26	Solving experimental problems	1h	Solving experimental problems for grade 9	tasks
27	Experimental work	1h	Study of oscillations of a spring pendulum	Finish calculations
28	Laboratory work No. 16	1h	Measuring the acceleration of free fall using a pendulum	Finish calculations
29		1h	Solving experimental problems for grade 9	Finish calculations
30	Solving experimental problems using a computer	1h	Solving experimental problems using a computer	Finish calculations
31	Solving experimental problems using a computer	1h	Solving experimental problems using a computer	Finish calculations
32	Solving experimental problems using a computer	1h	Solving experimental problems using a computer	Finish calculations
33	Tested task	1h	Test
34	General lesson	1h	Summing up and tasks for next year

LITERATURE:

Demonstration experiment in physics in high school./Ed. A. A. Pokrovsky. Part 1. - M.: Education, 1978.
Methods of teaching physics in grades 7-11 of secondary school./Edited by V.P. Orekhova and A.V. Usova. - M.: Education, 1999.
Enochovich A.S. Handbook of Physics. - M.: Education, 1978.
Martynov I.M., Khozyainova E.N. Didactic material on physics. 9th grade. - M.: Education, 1995.
Skrelin L.I. Didactic material on physics. 9th grade. – M.: Education, 1998.
Reader on Physics /Ed. B.I. Spassky. – M.: Education, 1982.
Rymkevich A.P., Rymkevich P.A. Collection of physics problems for grades 9 – 11. – M.: Education, 2000.
Stepanova G.N. Collection of problems in physics: For grades 9-11 in general education institutions. - M.: Education, 1998.
Gorodetsky D.N., Penkov I.A. Test work in physics. – Minsk “Higher School”, 1987.

Annex 1

Lesson No. 1: “Measurement of physical quantities and assessment of measurement errors.”

Lesson objectives: 1. To introduce students to the mathematical processing of measurement results and to teach how to present experimental data;

2. Development of computing abilities, memory and attention.

During the classes

The results of any physical experiment must be analyzed. This means that in the laboratory it is necessary to learn not only to measure various physical quantities, but also to check and find connections between them, to compare experimental results with the conclusions of theory.

But what does it mean to measure a physical quantity? What to do if the desired quantity cannot be measured directly and its value is found by the value of other quantities?

Measurement refers to the comparison of a measured quantity with another quantity taken as a unit of measurement.

The measurement is divided into direct and indirect.

In direct measurements, the value being determined is compared with a unit of measurement directly or using a measuring device calibrated in the appropriate units.

In indirect measurements, the required quantity is determined (calculated) from the results of direct measurements of other quantities that are related to the measured quantity by a certain functional relationship.

When measuring any physical quantity, you usually have to perform three sequential operations:

Selection, testing and installation of devices;
Observation of instrument readings and readings;
Calculation of the required value from measurement results, assessment of errors.

Errors in measurement results.

The true value of a physical quantity is usually impossible to determine absolutely accurately. Each measurement gives the value of the determined quantity x with some error?x. This means that the true value lies in the interval

x measurement - dx< х ист < х изм + dх, (1)

where xmeas is the value of x obtained during the measurement; ?х characterizes the accuracy of x measurement. The quantity x is called the absolute error with which x is determined.

All errors are divided into systematic, random and misses (errors). The causes of errors are very diverse. Understand possible reasons errors and reducing them to a minimum - this means conducting an experiment correctly. Clearly this is not an easy task.

Systematic is an error that remains constant or changes naturally with repeated measurements of the same quantity.

Such errors arise as a result of the design features of the measuring instruments, the inaccuracy of the research method, any omissions of the experimenter, as well as when inaccurate formulas and rounded constants are used for calculations.

A measuring instrument is a device that is used to compare the measured value with a unit of measurement.

Any device contains one or another systematic error, which cannot be eliminated, but the order of which can be taken into account.

Systematic errors either increase or decrease the measurement results, that is, these errors are characterized by a constant sign.

Random errors are errors whose occurrence cannot be prevented.

Therefore, they can have a certain influence on a single measurement, but with repeated measurements they obey statistical laws and their influence on the measurement results can be taken into account or significantly reduced.

Slips and gross errors are excessively large errors that clearly distort the measurement result.

This class of errors is most often caused by incorrect actions of the observer. Measurements containing misses and gross errors should be discarded.

Measurements can be taken in terms of their accuracy technical And laboratory methods.

In this case, they are satisfied with such accuracy that the error does not exceed a certain predetermined value, determined by the error of the measuring equipment used.

With laboratory measurement methods, it is necessary to more accurately indicate the value of the measured quantity than is allowed by its single measurement using a technical method.

Then several measurements are made and the arithmetic mean of the obtained values is calculated, which is taken as the most reliable value of the measured value. Then the accuracy of the measurement result is assessed (taking into account random errors).

From the possibility of carrying out measurements using two methods, it follows that there are two methods for assessing the accuracy of measurements: technical and laboratory.

Instrument accuracy classes.

To characterize most measuring instruments, the concept of reduced error E p (accuracy class) is often used.

The reduced error is the ratio of the absolute error?x to the limiting value xpr of the measured value (that is, its greatest value that can be measured on an instrument scale).

The given error, being essentially a relative error, expressed as a percentage:

E p = /dx/ x pr /*100%

According to the given error, devices are divided into seven classes: 0.1; 0.2; 0.5; 1.0; 1.5; 2.5; 4.

Devices of accuracy class 0.1; 0.2; 0.5 is used for precise laboratory measurements and is called precision.

In technology, devices of classes 1, 0 are used; 1.5; 2.5 and 4 (technical). The accuracy class of the device is indicated on the device scale. If there is no such designation on the scale, but this device is extracurricular, then its reduced error is more than 4%. In cases where the accuracy class is not indicated on the device, the absolute error is taken equal to half the value of the smallest division.

So, when measuring with a ruler, the smallest division of which is 1 mm, an error of up to 0.5 mm is allowed. For instruments equipped with a vernier, the instrument error is taken to be the error determined by the vernier (for a caliper - 0.1 mm or 0.05 mm; for a micrometer - 0.01 mm).

Appendix 2

Laboratory work: “Measuring the efficiency of an inclined plane.”

Equipment: wooden board, wooden block, tripod, dynamometer, measuring ruler.

Task: Investigate the dependence of the efficiency of an inclined plane and the gain in force obtained with its help from the angle of inclination of the plane to the horizon.

The efficiency of any simple mechanism is equal to the ratio of useful work A floor to perfect work A owl and is expressed as a percentage:

n = A sex / A owl *100% (1).

In the absence of friction, the efficiency of a simple mechanism, including an inclined plane, is equal to unity. In this case, the perfect work A of the force F t applied to the body and directed upward along the inclined plane is equal to useful work And the floor.

A gender = A owl.

Having designated the path traversed by the body along the inclined plane with the letter S, the height of the rise? , we get F*S=hgm.

In this case, the gain in strength will be equal to: k = gm/F=l/h.

In real conditions, the effect of friction reduces the efficiency of the inclined plane and reduces the gain in force.

To determine the efficiency of an inclined plane for the gain in force obtained with its help, the following expression should be used:

n = hgm/ F t l*100% (2), k = gm/F t (3).

The purpose of the work is to measure the efficiency of an inclined plane and the gain in force at different angles? its inclination to the horizon and explain the result obtained.

The order of work.

1. Assemble the installation according to Fig.1. Measure the height? and length l of the inclined plane (Fig. 2).

2. Calculate the maximum possible gain in force obtained for a given plane inclination (a=30).

3. Place the block on an inclined plane. After attaching the dynamometer to it, pull it up evenly along the inclined plane. Measure the traction force Ft.

4. Measure the gravity force mg of the block using a dynamometer and find the experimental value of the gain in force obtained using an inclined plane: k = gm/F t.

5. Calculate the efficiency of an inclined plane at a given angle of inclination

n = hgm/ F t l*100%

6. Repeat the measurements at other angles of inclination of the plane: a 2 =45?, a 3 =60?.

7. Enter the results of measurements and calculations into the table:

№	a	m, kg	h, m	l, m	F, N	To	n,%
1	30
2	45
3	60

8. Additional task

Compare the resulting theoretical dependence of n(a) and k(a) with the experimental results.

Control questions.

What is the purpose of using an inclined plane?
How can you increase the efficiency of an inclined plane?
How can you increase the strength gain obtained using an inclined plane?
Does the efficiency of an inclined plane depend on the mass of the load?
Explain qualitatively the dependence of the efficiency of an inclined plane and the gain in force obtained with its help on the angle of inclination of the plane.

Appendix 3

List of experimental tasks for 7th grade

Measuring the dimensions of the bar.
Measuring the volume of liquid using a beaker.
Measuring liquid density.
Measuring the density of a solid.

All work is carried out with calculation of errors and verification

dimensions.

Measurement body weight using a lever.
Calculation of the gain in the strength of the tools used (scissors, wire cutters, pliers)
Observation of the dependence of the kinetic energy of a body on its speed and mass.
Find out what the friction force depends on experimentally.

List of experimental tasks for 8th grade

Observation of the effects of electric current (thermal, chemical, magnetic and, if possible, physiological).
Calculation of the characteristics of a mixed connection of conductors.
Determination of conductor resistivity with error estimation.
Observation of the phenomenon of electromagnetic induction.

Observation of energy absorption during ice melting.
Observation of energy release during crystallization of hyposulfite.
Observation of energy absorption during evaporation of liquids.
Observation of the dependence of the rate of evaporation of a liquid on the type of liquid, its free surface area, temperature and rate of vapor removal.
Determination of air humidity in the office.

List of experimental works for grade 9

1.Measurement of the modules of angular and linear velocities of a body during uniform motion in a circle.
2.Measurement of the modulus of centripetal acceleration of a body during uniform motion in a circle.
3. Observation of the dependence of the modules of the tension forces of the threads on the angle between them at a constant resultant force.
4. Study of Newton's third law.

Observation of changes in the modulus of weight of a body moving with acceleration.
Clarification of the equilibrium conditions for a body having an axis of rotation when forces act on it.
Study of the law of conservation of momentum during elastic collision of bodies.
Measuring the efficiency of the moving unit.

Appendix 4

Experimental tasks

Measuring the dimensions of the bar

Instruments and materials (Fig. 2): 1) measuring ruler, 2) wooden block.

Work order:

Calculate the scale division value of the ruler.
Specify the limit of this scale.
Measure the length, width, height of the block with a ruler.
Write down the results of all measurements in a notebook.

Measuring the volume of liquid using a beaker

Devices and materials (Fig. 3):

measuring cylinder (beaker),
glass of water.

Work order

Calculate the scale division value of the beaker.
Draw a part of the beaker scale in your notebook and make a note explaining the procedure for calculating the scale division price.
Specify the limit of this scale.
Measure the volume of water in the glass using a beaker. " "
Write down the measurement result in your notebook.
Pour the water back into the glass.

Pour, for example, 20 ml of water into a beaker. After checking by the teacher, add more water to it, bringing the level to the mark, for example, 50 ml. How much water was added to the beaker?

Liquid density measurement

Instruments and materials (Fig. 14): 1) training scales, 2) weights, 3) measuring cylinder (beaker), 4) glass of water.

Work order

Write down: the value of the scale division of the beaker; the upper limit of the beaker scale.
Measure the mass of the glass of water using a scale.
Pour water from the glass into a beaker and measure the mass of the empty glass.
Calculate the mass of water in the beaker.
Measure the volume of water in the beaker.
Calculate the density of water.

Calculation of body mass by its density and volume

Instruments and materials (Fig. 15): 1) training scales, 2) weights, 3) a measuring cylinder (beaker) with water, 4) an irregularly shaped body on a thread, 5) a table of densities.

Work order(Fig. 15)

Measure your body volume using a beaker.
Calculate body weight.
Check your body weight calculation using a scale.
Write down the results of measurements and calculations in your notebook.

Calculating the volume of a body based on its density and mass

Instruments and materials (Fig. 15): 1) training scales, 2) weights, 3) a measuring cylinder (beaker) with water, 4) an irregularly shaped body on a thread, b) a table of densities.

Work order

Write down the substance that makes up the irregularly shaped body.
Find the density of this substance in the table.
Measure your body weight using a scale.
Calculate the volume of the body.
Check the result of calculating the volume of a body using a beaker.
Write down the results of measurements and calculations in your notebook.

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

Instruments and materials (Fig. 23): 1) dynamometer, 2) tribometer 3) weights with two hooks - 2 pcs., 4) sheet of paper, 5) sheet of sandpaper.

Work order

1. Prepare a table in your notebook to record the measurement results:

2. Calculate the value of the dynamometer scale division.
3.Measure the sliding friction force of a block with two loads:

4. Write down the measurement results in the table.

5. Answer the questions:

Does sliding friction force depend on:
a) from the type of rubbing surfaces?
b) from the roughness of rubbing surfaces?
In what ways can you increase and decrease the force of sliding friction? (Fig. 24):
1) dynamometer, 2) tribometer.

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

Instruments and materials: 1) dynamometer, 2) tribometer; 3) weights with two hooks - 2 pcs.

Work order

Calculate the value of the dynamometer scale division.
Place a block with a large edge on the tribometer ruler, and a load on it and measure the sliding friction force of the block along the ruler (Fig. 24, a).
Place a second weight on the block and again measure the sliding friction force of the block along the ruler (Fig. 24, b).
Place the block with the smaller edge on the ruler, place two weights on it again and again measure the sliding friction force of the block along the ruler (Fig. 24, V)
5. Answer the question: does the force of sliding friction depend on:
a) on the force of pressure, and if it depends, how?
b) on the area of the rubbing surfaces at a constant pressure force?

Measuring body weight using a lever

Equipment and materials: 1) lever-ruler, 2) measuring ruler, 3) dynamometer, 4) weight with two hooks, 5) metal cylinder, 6) tripod.

Work order

Hang the arm on the axle attached to the tripod coupling. Rotate the nuts on the ends of the lever to set it to a horizontal position.
Hang a metal cylinder to the left side of the lever, and a load to the right, having previously measured its weight with a dynamometer. Experimentally achieve balance between the lever and the load.
Measure the arms of the forces acting on the lever.
Using the lever equilibrium rule, calculate the weight of the metal cylinder.
Measure the weight of the metal cylinder using a dynamometer and compare the result with the calculated one.
Write down the results of measurements and calculations in your notebook.
Answer the questions: will the result of the experiment change if:

balance the lever with a different arm length of the forces acting on it?
hang the cylinder on the right side of the lever, and the balancing weight on the left?

Calculation of the gain in the strength of instruments in which leverage is applied

"Device and materials (Fig. 45): 1) scissors, 2) wire cutters, 3) pliers, 4) measuring ruler.

Work order

Familiarize yourself with the design of the tool offered to you, which uses a lever: find the axis of rotation, the points of application of forces.
Measure the force arms.
Calculate approximately within what limits the value can vary
The toy is valid when using this tool.
Write down the results of measurements and calculations in your notebook.
Answer the questions:

How should the material being cut be positioned in the scissors to obtain the greatest gain in strength?
How should you hold the pliers in your hand to get the greatest gain in strength?

Observation of the dependence of the kinetic energy of a body on its speed and mass

Equipment and materials (Fig. 50): I) balls different weights- 2 pcs., 2) gutter, 3) block, 4) measuring tape, 5) tripod. Rice. 50.

Work order

Support the gutter in an inclined position using a tripod, as shown in Figure 50. Place a wooden block at the lower end of the gutter
Place a ball of smaller mass in the middle of the gutter and, releasing it, watch how the ball, rolling off the gutter and hitting a wooden block, moves the latter a certain distance, doing work to overcome the friction force.
Measure the distance the block has moved.
Repeat the experiment, launching the ball from the upper end of the chute, and again measure the distance over which the block has moved.
Launch a ball of larger mass from the middle of the chute and measure the movement of the block again.

Measuring the modules of angular and linear velocities of a body during uniform motion in a circle

Equipment and materials* 1) a ball with a diameter of 25 mm on a thread 200 mm long, 2) a measuring ruler 30-35 cm with millimeter divisions, 3) a clock with a second hand or a mechanical metronome (one per class).

Work order

Lift the ball by the end of the thread above the ruler and set it in uniform motion around the circle so that when rotating, each time it passes through the zero and, for example, tenth division of the scale (Fig. 9). To obtain stable movement of the ball, place the elbow of the hand holding the thread on the table
Measure the time, for example, 30 full revolutions of the ball.
Knowing the time of movement, the number of revolutions and the radius of rotation, calculate the absolute values of the angular and linear velocities of the ball relative to the table.
Write down the results of measurements and calculations in your notebook.
Answer the questions:

Measuring the modulus of centripetal acceleration of a body during uniform circular motion

The equipment and materials are the same as in task 11.

Work order

Follow steps 1, 2 tasks 11.
Knowing the time of movement, the number of revolutions and the radius of rotation, calculate the module of the centripetal acceleration of the ball.
Write down the results of measurements and calculations in your notebook:
Answer the questions:

How will the module of the centripetal acceleration of the ball change if the number of its revolutions per unit time is doubled?
How will the module of the centripetal acceleration of the ball change if the radius of its rotation is doubled?

Observation of the dependence of the moduli of tension forces on the threads on the angle between them at a constant resultant force

Equipment and materials: 1) a weight weighing 100 g with two hooks, 2) training dynamometers - 2 pcs., 3) a thread 200 mm long with loops at the ends.

Work order

What are the moduli of tension forces of the threads? Did they change during the experience?
What is the modulus of the resultant of the two thread tension forces? Did it change during the experience?
What can be said about the dependence of the moduli of tension forces on the threads on the angle between them at a constant resultant force?

Studying Newton's Third Law

Equipment and materials: I) training dynamometers - 2 pcs., 2) thread 200 mm long with loops at the ends.

Work order

With what modulus force does the left dynamometer act on the right one? In which direction is this force directed? Which dynamometer is it attached to?
With what modulus force does the right dynamometer act on the left one? In which direction is this force directed? Which dynamometer is it attached to?

3. Increase dynamometer interaction. Notice their new readings.

4. Connect the dynamometers with a thread and tighten it.

5. Answer the questions:

With what modulus force does the left dynamometer act on the thread?
With what absolute force does the right dynamometer act on the thread?
With what modulus force does the thread stretch?

6. Draw a general conclusion from the experiments performed.

Observation of changes in the modulus of weight of a body moving with acceleration

Equipment and materials: 1) training dynamometer, 2) a weight weighing 100 g with two hooks, 3) a thread 200 mm long with loops at the ends.

Work order

Did the speed of the load change as it moved up and down?
How did the modulus of the weight of the load change as it moved rapidly up and down?

4. Place the dynamometer on the edge of the table. Tilt the load to the side at a certain angle and release (Fig. 18). Observe the dynamometer readings as the load oscillates.

5. Answer the questions:

Does the speed of the load change as it oscillates?
Do the acceleration and weight of the load change as it oscillates?
How do the centroidal acceleration and the weight of the load change as it oscillates?
At which points of the trajectory are the centripetal acceleration and the absolute weight of the load the greatest, and at which are the least? Figure 18.

Clarification of the equilibrium conditions of a body having an axis of rotation under the action of forces on it

Equipment and materials: 1) a sheet of cardboard measuring 150X150 mm with two thread loops, 2) training dynamometers - 2 pcs., 3) a sheet of cardboard measuring 240X340 mm with a nail driven in, 4) a student's square, 5) a measuring ruler 30-35 cm with millimeter divisions, 6) pencil.

Work order

1. Place a piece of cardboard over the nail. Hook the dynamometers onto the hinges, pull them with forces of approximately 2 and 3 N and position the hinges at an angle of 100-120° to each other, as shown in Figure 27. Make sure that the cardboard sheet returns to its state when tilted to the side

Rice. 27. Measure the modules of the applied forces (neglect the gravity of the cardboard).

2. Answer the questions:

How much force is acting on the cardboard?
What is the modulus of the resultant forces applied to the cardboard?

3. On a sheet of cardboard, draw straight line segments along which the forces act, and using a square, construct the shoulders of these forces, as shown in Figure 28.

4. Measure the force arms.

5. Calculate the moments of the acting forces and their algebraic sum. Under what condition is a body with a fixed axis of rotation in a state of equilibrium? Rice. 28. Write the answer in your notebook.

Study of the law of conservation of momentum during elastic collision of bodies

Equipment and materials: 1) balls with a diameter of 25 mm - 2 pcs., 2) thread 500 mm long, 3) a tripod for frontal work.

Work order

What is the total momentum of the balls before interaction?
Did the balls acquire the same impulses after interaction?
What is the total momentum of the balls after interaction?

4. Release the retracted ball and notice the deflection of the balls after impact. Repeat the experiment 2-3 times. Deflect one of the balls 4-5 cm from the equilibrium position, and leave the second one alone.

5. Answer the questions in step 3.

6. Draw a conclusion from the experiments done

Measuring the efficiency of the moving unit

Equipment and materials: 1) block, 2) training dynamometer, 3) measuring tape with centimeter divisions, 4) weights weighing 100 g with two hooks - 3 pcs., 5) tripod for frontal work, 6) thread 50 cm long with loops at the ends.

Work order

Assemble the installation with a movable block, as shown in Figure 42. Throw a thread through the block. Hook one end of the thread onto the tripod leg, the other onto the hook of the dynamometer. Hang three weights weighing 100 g each from the block holder.
Take the dynamometer in your hand, position it vertically so that the block with weights hangs on the threads, and measure the modulus of the tension force of the thread.
Raise the loads evenly to a certain height and measure the modules of movement of the loads and the dynamometer relative to the table.
Calculate the useful and perfect work relative to the table.
Calculate the efficiency of the moving unit.
Answer the questions:

What gain in strength does the movable block give?
Is it possible to get a gain in work using a moving block?
How to increase the efficiency of a moving unit?

Appendix5

Requirements for the level of training of secondary school graduates.

1. Master the methods of scientific knowledge.

1.1. Assemble experimental setups using a description, drawing or diagram and conduct observations of the phenomena being studied.

1.2. Measure: temperature, mass, volume, force (elasticity, gravity, sliding friction), distance, time interval, current strength, voltage, density, period of oscillation of the pendulum, focal length of the collecting lens.

1.3. Present measurement results in the form of tables, graphs and identify empirical patterns:

changes in body coordinates over time;
elastic forces from spring elongation;
current in the resistor versus voltage;
mass of a substance versus its volume;
body temperature versus time during heat exchange.

1.4. Explain the results of observations and experiments:

the change of day and night in the reference system associated with the Earth and in the reference system associated with the Sun;
greater compressibility of gases;
low compressibility of liquids and solids;
processes of evaporation and melting of matter;
evaporation of liquids at any temperature and its cooling during evaporation.

1.5. Apply experimental results to predict the values of quantities characterizing the course of physical phenomena:

the position of the body when it moves under the influence of force;
extension of the spring under the action of a suspended load;
current strength at a given voltage;
the temperature value of the cooling water at a given point in time.

2. Know the basic concepts and laws of physics.

2.1. Define physical quantities and formulate physical laws.

2.2. Describe:

physical phenomena and processes;
changes and transformations of energy in the analysis of: free fall of bodies, movement of bodies in the presence of friction, oscillations of thread and spring pendulums, heating of conductors by electric current, melting and evaporation of matter.

2.3. Calculate:

resultant force using Newton's second law;
momentum of a body, if the speed of the body and its mass are known;
the distance over which sound travels in a certain time at a given speed;
kinetic energy of a body at a given mass and speed;
potential energy of interaction of a body with the Earth and the force of gravity for a given body mass;
the energy released in a conductor during the passage of electric current (at a given current and voltage);
energy absorbed (released) when heating (cooling) bodies;

2.4. Construct an image of a point in a plane mirror and a converging lens.

3. Perceive, process and present educational information in various forms (verbal, figurative, symbolic).

3.1. Call:

sources of electrostatic and magnetic fields, methods of their detection;
energy conversion in engines internal combustion, electric generators, electric heating devices.

3.2. Give examples:

relativity of speed and trajectory of movement of the same body in different systems countdown;
change in the speed of bodies under the influence of force;
deformation of bodies during interaction;
manifestation of the law of conservation of momentum in nature and technology;
oscillatory and wave movements in nature and technology;
environmental consequences of the operation of internal combustion engines, thermal, nuclear and hydroelectric power plants;
experiments confirming the main provisions of the molecular kinetic theory.

3.4. Highlight the main idea in the text you read.

3.5. Find answers to the questions posed in the text you read.

3.6. Take notes on the text you read.

3.7. Define:

intermediate values of quantities according to tables of measurement results and constructed graphs;
the nature of thermal processes: heating, cooling, melting, boiling (according to graphs of changes in body temperature over time);
resistance metal conductor(according to the oscillation schedule);
according to the graph of coordinates versus time: to the coordinates of the body at a given point in time; periods of time during which the body moved at a constant, increasing, decreasing speed; time intervals of force action.

3.8. Compare the resistance of metal conductors (more - less) using graphs of current versus voltage.

The effectiveness of using experimental tasks in lessons is largely determined by their manufacturability, unpretentious equipment, and the breadth of the phenomena under consideration. Based on the simplest equipment and even everyday objects, the experimental task brings physics closer to us, transforming it in the students’ minds from an abstract system of knowledge in science that studies “the world around us.”

Mechanics

Task 1. Friction coefficient

Exercise. Measure the sliding friction coefficient of a wooden block on the surface of a board (ruler).

Equipment: block, board, tripod with foot, ruler 30(40) long cm.

Possible way solutions. We place the block on the board, in accordance with Figure 4. Gradually raising one end of the board, we obtain an inclined plane and achieve uniform sliding of the block. Since the static friction force is much greater than the sliding friction force, it is necessary to push the bead a little at the beginning of sliding. To fix the desired tilt, use a tripod. We measure the height A and the length of the base of the inclined plane b.

Measurements and error analysis:

We repeat the experiment several times. In this case, this must be done mainly because it is difficult to achieve uniform sliding of the block along the plane. The results are recorded in Table 2.

table 2

Measurement errors


a, cm	Yes, cm	(Yes) 2 ,cm 2	in, cm	Db, cm	(Db) 2 ,cm 2



<a>=12,2		U( a) 2 = 1,81			U( b) 2 = 0,32

In addition to random errors, the total error, of course, also includes the usual reference errors: Yes = Db = 0.5 cm.This amounts to:

Thus we get:

a = 12.2 ± 1.1 cm, d = 8.6%

b = 27.4 ± 0.7 cm, d = 2.6%

Based on the results of the first experiment:

The final result of the friction coefficient measurement is:

m = 0.46 ± 0.05 d = 10.9%

Task 2. Measuring the height of a house

Exercise. Imagine that you were asked to use an empty tin can and a stopwatch to measure the height of a house. Would you be able to cope with the task? Tell us how to act.

Clue. If a can is thrown from the roof of a house, the sound of the can hitting the ground will be clearly audible.

Solution. Standing on the roof of the house, you need to release the can from your hands while simultaneously pressing the stopwatch start button. When you hear the sound of the can hitting the ground, you should stop the stopwatch. Stopwatch readings t are made up of the time the jar falls t 1 and time t 2, during which the sound of its impact on the earth’s surface will reach the observer.

The first time is related to the height of the house h in the following way:

whereas the connection between h and t 2 has the form

Where With- speed of sound, which in calculations we will set equal to 340 m/sec.

Defining t 1 and t 2 of these expressions and substituting their values into the formula connecting t 1 , t 2 and t, we obtain the irrational equation

From which you can find the height of the house.

In an approximate calculation (especially if the house is low), the second term on the left can be considered small and discarded. Then

Molecular physics

Task 3. Pencil

Exercise. Estimate the mechanical work that must be done in order to evenly raise a pencil floating in a vessel to the level of its lower end touching the surface of the water. Consider the position of the pencil to be vertical. Density of water With 0 = 1000 kg/m 3 .

Equipment: round pencil, almost full water bottle, ruler.

Possible solution. We lower the pencil into the bottle - it will float like a float, in accordance with Figure 5. Let L- the length of the entire pencil, V- its volume, h- the length of the part of the pencil immersed in water, V 1 - its volume, S- cross-sectional area and d- pencil diameter. We'll find average density pencil With from the body floating condition:

With 0 gSh= сgSL, where With= With 0 hL.

Let's assume that we pull a pencil out of water at a constant speed using a dynamometer. When the pencil floats freely, the dynamometer shows zero. If the pencil is completely pulled out of the water, the dynamometer will show a force equal to the weight R pencil:

F = P = mg = сgV = с0hLgSL = с0hgрd24

It turns out that the readings of the dynamometer when pulling the pencil out of the water change from 0 to P according to the linear law, in accordance with Figure 6. In this case, the mechanical work A will be equal to the area of the selected triangle:

A= 12Ph= With 0 h 2gрd 2 8.

For example, when h= 13,4 cm And d = 7,5 mm work is about 0.004 J.

Task 4. Alloy

Exercise. Determine the percentage (by weight) of tin in tin-lead solder. Assume that the volumes of lead and tin in the alloy are conserved. Lead Density With c = 11350 kg/m 3 , tin With 0 = 7300 kg/m 3 .

Equipment: ruler, weight (nut), cylindrical piece of solder, caliper or micrometer. Possible solution. This task is similar to Archimedes' task of determining the proportion of gold in the royal crown. However, for experiments, tin-lead solder is easier to obtain than corona.

Measuring the diameter of a piece of solder D and its length L, find the volume of a cylindrical piece of solder:

V =рD 2 L 4

We will determine the mass of solder by making lever scales. To do this, balance the ruler on the edge of the table (on a pencil, on a ballpoint pen, etc.). Then, using a nut of known mass, we balance a piece of solder on a ruler and, using the equality of the moments of force, we find the mass of the solder m. Let us write down the obvious equalities for the masses, volumes and densities of lead and tin:

m = m c +m o = ccV c +s o V o , V = V c +V o .

Solving these equations together, we find the volume of tin, its mass and its share in the total mass:

V o = rh o cV?mrh o c?rh oo , mo = с o V o , m o m = rh oo V o m

Problem 5. Surface tension

Exercise. Determine the coefficient of surface tension of water.

Equipment: plate, water, spoon, ruler, piece of straight aluminum wire 15-20 long cm and density 2700 kg/m 3 , micrometer, alcohol, cotton wool.

Possible solution. Pour an almost full plate of water. Place a wire on the edge of the plate so that one end touches the water and the other is outside the plate. The wire serves two functions: it is a lever scale and an analogue of the wire frame that is usually pulled out of the water to measure surface tension. Depending on the water level, different positions of the wire may be observed. The most convenient for calculations and measurements is the horizontal arrangement of the wire at a water level of 1-1.5 mm below the edge of the plate, in accordance with Figure 7. Using a spoon, you can adjust the level by adding or draining water. The wire should be pulled out of the plate until the film of water under the wire begins to break. In this extreme position the film has a height of 1.5-2 mm, and we can say that the surface tension forces applied to the wire are directed almost vertically downward.

Let m- mass of wire, L = L 1 + L 2 - wire length, m/L- mass per unit length of wire. Let us write down the condition for the equilibrium of the wire relative to the edge of the plate, i.e. equality of moments of forces:

F p (L 1 ?x 2)+m 1 gL 12 = m 2 gL 22 .

Let's substitute the surface tension force here F p =2x at, masses

m 1 =L 1 mL, m 2 = L 2 mL, m= cV= srd 2 L 4

and express the surface tension coefficient at. Measurements and calculations will be simplified if water wets the entire length L 1 . Finally we get

at= srd 2 g 8((LL 1 ?1) 2 ?1).

Quantities L And L 1 are measured with a ruler, and the diameter of the wire d- micrometer.

For example, when L = 15 cm, L 1 = 5,4 cm, d = 1,77 mm we get O = 0,0703 N/m which is close to table value 0,0728 N/m.

Problem 6. Air humidity

Exercise. Determine the relative humidity in the room.

Equipment: glass room thermometer, household refrigerator, table of saturated water vapor pressures at different temperatures.

Possible solution. In the conventional method of measuring humidity, the object is cooled below its dew point and it "fogs up." Let's do the opposite. Refrigerator temperature (about +5 ° C) is much lower than the dew point for room air. Therefore, if you take a cooled glass thermometer out of the refrigerator, it will immediately “fog up” - the glass case will become opaque from moisture. Then the thermometer will begin to heat up, and at some point the condensed moisture on it will evaporate - the glass will become transparent. This is the dew point temperature, from which the relative humidity can be calculated using a table.

Problem 7. Evaporation

Exercise. Pour an almost full glass of water and place it in a warm place in the room so that the water evaporates faster. Measure with a ruler First level water and record the start time of the experiment. After a few days, the water level will drop due to evaporation. Measure new level water and record the end time of the experiment. Determine the mass of water evaporated. On average, how many molecules escape from the surface of the water in 1 second? Approximately how many molecules are there on the surface of the water in the glass? Compare these two numbers. Take the diameter of a water molecule to be equal to d 0 = 0,3 nm. Knowing the specific heat of vaporization, determine the rate of heat transfer ( J/s) water from environment.

Possible solution. Let d- inner diameter of the glass, With- density of water, M- molar mass of water, r- specific heat of vaporization, D h- decrease in water level over time t. Then the mass of evaporated water is

m= cv= With D hS= With D hрd 2 4.

This mass contains N = mN A /M molecules, where N A- Avogadro's constant. The number of molecules evaporated in 1 second is

N 1 = Nt= mN A Mt.

If S= pd 2/4 is the surface area of water in a glass, and S 0 = pd 2 0 /4 is the cross-sectional area of one molecule, then on the surface of water in a glass there is approximately

N 2 = SS 0 = (dd 0) 2 .

Water receives heat per unit time for evaporation

Qt= rmt.

If you make any calculations related to molecules, you always get interesting results. For example, let in time t= 5 days in a glass with diameter d = 65 mm the water level dropped by D h = 1 cm. Then we get that 33 turned into steam G water, for 1 With evaporated N 1 = 2.56?10 18 molecules, on the surface of the water in the glass there were N 2 = 4.69?1016 molecules, and 0.19 came from the environment W heat. The interesting thing is the attitude N 1 /N 2? 54, from which it is clear that for 1 With As many molecules evaporated as could fit in a glass in 54 layers of water.

Problem 8. Dissolution

Exercise. By pouring salt or sugar into boiling water, you will notice that the boiling stops for a short time due to the decrease in water temperature. Determine the amount of heat required to dissolve 1 kg baking soda in water at room temperature.

Equipment: homemade calorimeter, thermometer, water, soda, graduated cylinder (glass), load of known mass (nut weighing 10 G), plastic spoon.

Possible solution. The task includes an additional design task for the manufacture of a simple homemade calorimeter. For the internal vessel of the calorimeter, take a regular aluminum can with a volume of 0.33 liters. The top lid of the jar is removed so that an aluminum glass is obtained (weighing only 12 G) with a rigid upper rim. A slot is made inside the top rim so that the water can completely drain out of the jar. The outer plastic shell is made on the basis of a plastic bottle with a volume of 1.5 l. The bottle is cut into three parts, top part is removed, and the middle and lower parts are inserted into each other with some force and tightly fix the inner aluminum can in a vertical position. (If there is no calorimeter, then experiments can be carried out in a disposable plastic cup, the mass and heat transfer of which can be neglected).

First you need to make two measurements: 1) determine how much soda fits in a spoon (to do this, you need to look in a culinary reference book or “scoop out” a packet of soda of a known mass with this spoon); 2) decide on the amount of water - in a small amount of water the solution will immediately become saturated and part of the soda will not dissolve, in large quantities The water temperature will change by fractions of a degree, making measurements difficult.

Obviously, the amount of heat required to dissolve a substance is proportional to the mass of this substance: Q~m. To record equality, you should enter a proportionality coefficient, for example z, which can be called “specific heat of solution”. Then

Q= zm.

The dissolution of soda is carried out due to the energy released when the vessel with water cools. The value of z is found from the following heat balance equation:

mvcv(t 2 -t 1 )+ma cc (t 2 -t 1 ) = zm.

Where m v is the mass of water in the calorimeter, m a is the mass of the internal aluminum cup of the calorimeter, m- mass of dissolved soda, ( t 2 -t 1) - decrease in temperature in the calorimeter. The mass of the internal vessel of the calorimeter can be easily found using the rule of moments of forces, balancing the vessel and a load of known mass using a ruler and thread.

Measurements and calculations show that when m= 6 g and m v = 100 G the water cools down by 2-2.5 degrees C, and the value z turns out to be equal to 144-180 kJ/kg.

Task 9. Pot capacity

Exercise. How can you find the capacity of a pan using scales and a set of weights?

Clue. Weigh the empty pan, and then the pan with water.

Solution. Let the mass of the empty pan be m 1, and after filling with water it is m 2. Then the difference m 2 -m 1 gives the mass of water in the volume of the pan. Dividing this difference by the density of water With, find the volume of the pan:

Problem 10. How to separate the contents of a glass

Exercise. There is a cylindrical glass filled to the brim with liquid. How to divide the contents of a glass into two completely equal parts, having another vessel, but of a different shape and slightly smaller size?

Clue. Think about how you can draw a plane dividing the cylinder into two parts of equal volume.

Solution. If through points M And N mentally draw the plane as shown in Figure 1 A, then it will cut the cylinder into two symmetrical and therefore equal in volume figures, in accordance with Figure 8. From here follows the solution to the problem.

Gradually tilting the glass, you need to pour out the liquid it contains until the bottom just appears (Figure 1 b). At this moment, exactly half of the liquid will remain in the glass.

Electricity

Problem 11. Electric black box

A black box is an opaque, closed box that cannot be opened to be examined. internal organization. Inside the box there are several electrical elements connected to each other in a simple electrical circuit. Typically, such elements are: current sources, fixed and variable resistors, capacitors, inductors, semiconductor diodes. There are several terminals on the outside of the box.

The main goal of the “black box” task: having made a minimum number of electrical measurements using external leads, “decipher” the “black box”, i.e.:

- establish which electrical devices are inside the “black box”.
- establish a diagram of their connection.
- determine the values (values of resistors, capacitances, etc.)

Exercise. Three resistors are connected to each other and placed in a “black box” with three terminals, in accordance with Figure 9. Exactly the same resistors are connected to each other in a different way and placed in a second “black box” with three terminals. Determine the resistance of each resistor. Jumpers are prohibited.

Equipment: multimeter.

Measuring the resistance between the terminals gave the following results:

Box No. 1: R 1-2 = 12Ohm, R 2-3 = 25Ohm, R 1-3 = 37Ohm

Box No. 2: R 1-2 = 5,45Ohm, R 2-3 = 15Ohm, R 1-3 = 20,45Ohm

Possible solution. There are four possible ways of connecting three resistors to three outer terminals so that the three measurements give different meaning resistances:

1) sequential, 2) mixed, 3) star, 4) triangle, in accordance with Figure 10.

We will show the sequence of searching for answers.

A characteristic feature of the first two schemes is that one of the measurements is equal to the sum of the other two, which corresponds to the conditions of the problem:

Consequently, in one box there is a serial connection, but then in the other there is a mixed connection, since the measurement results do not match, although the resistor values are the same.

It is known that the relation is always satisfied

And since R 1-3 on the left more than R 1-3 on the right, then in the left box (No. 1) there is a serial connection, and in the right (No. 2) there is a mixed connection.

The series connection in the left box contains resistors with values of 12 or 25 Ohm. Since neither one nor the other value is observed as part of a mixed connection, therefore, the value of one of the resistors R 1 = 15Ohm.

Other denominations: R 2 = 12Ohm And R 3 = 10Ohm.

Obviously, the same results can be reached using a different chain of reasoning.

Note also that 5 more combinations of schemes with two “black boxes” from the above four are possible. The most cumbersome mathematical part of the problem is to “decipher” the black box, which is known to contain a triangle.

In conclusion, we note that not everything can go as smoothly as in this example. Values of resistance or other electrical quantities naturally contain errors. And, for example, the ratio can only be satisfied approximately.

Problem 12. Room temperature

Exercise. There is snow outside the window, but the room is warm. Unfortunately, there is nothing to measure the temperature with - there is no thermometer. But there is a battery, a very accurate voltmeter and the same ammeter, as much copper wire as you like and a detailed physical reference book. Is it possible to use them to find the air temperature in the room?

Clue. When a metal is heated, its resistance increases linearly.

Solution. Let's connect a battery in series, a coil of wire and turn on the ammeter so that it shows the voltage on the coil, in accordance with Figure 11. We record the instrument readings and calculate the resistance of the coil at room temperature:

After this, we will bring snow from the street, immerse a coil of it in it and, after waiting a little so that the snow begins to melt and the wire begins to warm up, we will determine the resistance of the wire in the same way R 0 at the temperature of melting snow, i.e. at 0 є WITH. Using then the relationship between the resistance of the conductor and its temperature

find the air temperature in the room:

When calculating, the value of the temperature coefficient of resistance is used b, taken from the reference book. In the room temperature range for pure copper b= 0,0043 hail - 1 . If the content of impurities in the copper from which the wire is made is not particularly high, and electrical measuring instruments have an accuracy class of 0.1, then the air temperature can be determined with an error of significantly less than one degree.

Optics

Problem 13.

Exercise. You need to find the radius of a spherical mirror (or radius of curvature concave lenses) using a stopwatch and a steel ball of known radius. How to do it?

Clue. The center of a ball rolling on the surface of a mirror makes the same motion as a pendulum.

Solution. Place the mirror horizontally and lower the ball onto it. If the ball is not lowered to the lowest point, it will begin to move along the surface of the mirror. It is not difficult to guess that if the ball moves without rotation (i.e. slides along the surface of the mirror), then its movement is completely similar to the movement of a pendulum with a suspension length R-r. Then from the pendulum formula

we can find the quantity we are interested in:

Period T determined using a stopwatch, and r known by condition.

Since the friction is usually high enough to cause the ball to move along the surface of the mirror with rotation, this solution does not agree well with experiment. In fact

Here is an example of a research task for the entire lesson.

Problem 14. Features of oscillation of a torsion pendulum.

Exercise. Explore the features of oscillation of a torsional pendulum and describe the main laws of its movement.

Equipment: tripod with coupling and foot, pieces of copper, steel and nichrome wire length about 1m and various diameters, for example 0.3, 0.50, 0.65, 1.0 mm, thin light wooden stick length 15-20 cm, plasticine, paperclip, ruler, protractor, stopwatch.

The general appearance of the torsion pendulum should be in accordance with Figure 12. A paper clip, bent in a certain way, serves to balance the rod with weights. The pendulum, removed from the state of equilibrium, begins to perform a rotational-oscillatory motion.

In advance, you need to make pairs of balls of different weights from plasticine. The masses of the balls are proportional to the cube of their diameters, so it is possible to build a series, for example: m 1 = 1, m 2 = 2,5, m 3 = 5,2, m 3 = 6,8, m 4 = 8,3 rel. units

The diameter of the wires can be given to students in advance or they can be given the opportunity to make these measurements themselves using a caliper or micrometer.

Note. The success of the study largely depends on correct selection equipment, especially the diameters of the issued wires. In addition, it is desirable that the suspension of the torsion pendulum be in a tense state during the experiments, for which the masses of the loads must be large enough.

The subject of the study of a torsional pendulum follows from the assumption of the harmonic nature of its oscillations. The general list of experimental observations that can be carried out on this problem and on the proposed equipment is quite large. We present the simplest and most accessible ones.

- Does the period of oscillation depend on the amplitude (angle of rotation)?
- Does the period of oscillation depend on the length of the pendulum's suspension?
- Does the period of oscillation of a pendulum depend on the mass of the loads?
- Does the period of oscillation of a pendulum depend on the position of the weights on the rod?
- Does the period of oscillation depend on the diameter of the wire?

Naturally, it is required not only to answer the questions posed in monosyllables, but also to examine the nature of the expected dependencies.

Using the technique of analogies, we put forward hypotheses about the oscillations of a torsion pendulum, comparing it with a mathematical pendulum studied in the school curriculum. We take as a basis the period of oscillation and its dependence on various parameters of the pendulum. We outline the following hypotheses. Period of oscillation of a torsion pendulum:

At small angles of rotation it does not depend on the amplitude;

- proportional to the square root of the length of the suspension - T;
- proportional to the square root of the mass of the load - T;
- proportional to distance from the suspension center to the load centers - Tr;
- inversely proportional to the square of the wire diameter - T1/d 2 .

In addition, the oscillation period depends on the suspension material: copper, steel, nichrome. There are also a number of hypotheses here, we suggest testing them yourself.

1. We study the dependence of the period of oscillation of the pendulum on the amplitude (angle of rotation). The measurement results are presented in Table 3:

Table 3

Dependence of the period of oscillation of a pendulum on amplitude

L= 60cm, m = 8,3g, r = 12cm, d = 0,5mm

Conclusion. Within limits of up to 180, the dependence of the period of oscillation of the torsion pendulum on the amplitude is not detected. The scatter of measurement results can be explained by errors in measuring the oscillation period and random reasons.

To “open” other dependencies, you need to change only one parameter, leaving all others unchanged. Mathematical processing of results is best done graphically.

2. We study the dependence of the period of oscillation of the pendulum on its length: T = f(l). At the same time, we do not change m, r, d. The measurement results are presented in Table 4:

Table 4

Dependence of the period of oscillation of a pendulum on length

m = 8,3rel. units, r = 12cm, d = 0,5mm

Dependency graph T from l represents a curve of an increasing line, similar to a dependence, in accordance with Figure 13 A T 2 = l, in accordance with Figure 13, b.

Conclusion. The period of oscillation of a torsion pendulum is directly proportional to the square root of the length of the suspension. Some scatter of points can be explained by measurement errors in the period of oscillation and the length of the pendulum

3. We study the dependence of the period of oscillation of the pendulum on the mass of the loads: T=f(m). At the same time, we do not change l, r, d. The measurement results are presented in Table 5:

Table 5

Dependence of the period of oscillation of a pendulum on the mass of loads

l = 0,6m, r = 12cm, d = 0,5mm

Dependency graph T from m represents a curve of an increasing line, similar to a dependence, in accordance with Figure 14 A. To make sure of this, we build a dependency T 2 =f(m), according to Figure 14 b.

Conclusion. The period of oscillation of a torsion pendulum is directly proportional to the square root of the mass of the loads. Some scatter of points can be explained by measurement errors of the oscillation period and masses of the loads, as well as random reasons.

4. We study the dependence of the period of oscillation of the pendulum on the position of the weights: T = f(r). At the same time, we do not change l, m, d. The measurement results are presented in Table 6:

Table 6

Dependence of the period of oscillation of the pendulum on the position of the weights

m = 8,3rel. units, l = 0,6m, d = 0,5mm

Conclusion. The period of oscillation of a torsion pendulum is directly proportional to the distance r. Some scatter of points can be explained by measurement errors of the oscillation period and distance r, as well as random reasons.

We study the dependence of the period of oscillation of the pendulum on the diameter of the wire: T = f(d), in accordance with Figure 15 . At the same time we do not change m, r, l.

The measurement results are presented in Table 7.

Table 7

Dependence of the period of oscillation of a pendulum on the diameter of the wire

m = 8.3 relative units, r = 12 cm, l = 0.6 m

Dependency graph T from d represents a descending curve, in accordance with Figure 16 A. It can be assumed that this is a dependency where n= 1, 2, 3, etc. To check these assumptions, it is necessary to build graphs, etc. Of all such graphs, the most linear is the graph, in accordance with Figure 16 b.

Conclusion. The period of oscillation of a torsion pendulum is inversely proportional to the square of the diameter of the suspension wire. Some scatter of points can be explained by measurement errors of the oscillation period and wire diameter d, as well as random reasons.

The studies carried out allow us to conclude that the period of oscillation of a torsion pendulum should be calculated according to the formula, where k- proportionality coefficient, which also depends on the elastic properties of the suspension material - torsion modulus, shear modulus.

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