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Changes in the exam in physics. Changes in the exam in physics Fipi demo version of physics |
August 22, 2017 In 2018, in the KIMs of the Unified State Examination in Physics, students will again find 32 tasks. Recall that in 2017 the number of tasks was reduced to 31. An additional task will be a question on astronomy, which, by the way, is again being introduced as a compulsory subject. It is not entirely clear, however, due to what hours, but, most likely, physics will suffer. So, if in the 11th grade you do not count the lessons, then the ancient science of the stars is probably to blame. Accordingly, you will have to prepare more on your own, because the volume of school physics will be extremely small in order to somehow pass the exam. But let's not talk about sad things. The question on astronomy is number 24 and the first test part ends with it. The second part, respectively, has shifted and now begins with the 25th issue. Other than that, no major changes were found. The same short answer questions, matching and multiple choice tasks, and, of course, short and long answer tasks. Exam tasks cover the following sections of physics:
Molecular physics(molecular-kinetic theory, thermodynamics). Electrodynamics and fundamentals of SRT(electric field, direct current, magnetic field, electromagnetic induction, electromagnetic oscillations and waves, optics, fundamentals of SRT). The quantum physics(particle-wave dualism, physics of the atom and atomic nucleus). Below you can familiarize yourself with the approximate tasks of the USE in 2018 in a demo version from FIPI. As well as familiarize yourself with the codifier and specification.
In 2018, graduates of grade 11 and institutions of secondary vocational education will take the USE 2018 in physics. The latest news regarding the Unified State Examination in Physics in 2018 is based on the fact that some changes will be made to it, both major and minor. What is the meaning of changes and how many of themThe main change related to the Unified State Examination in Physics, compared to previous years, is the absence of a test part with a choice of answers. This means that preparation for the exam should be accompanied by the student's ability to give short or detailed answers. Therefore, it will no longer be possible to guess the option and score a certain number of points and you will have to work hard. A new task 24 has been added to the basic part of the exam in physics, which requires the ability to solve problems in astrophysics. By adding No. 24, the maximum primary score has increased to 52. The exam is divided into two parts according to difficulty levels: a basic one of 27 tasks, involving a short or full answer. In the second part there are 5 tasks of an advanced level, where you need to give a detailed answer and explain the course of your solution. One important nuance: many students skip this part, but even trying to complete these tasks can get from one to two points. All changes in the exam in physics are made in order to deepen the preparation and improve the assimilation of knowledge in the subject. In addition, the elimination of the test part motivates future applicants to accumulate knowledge more intensively and reason logically. Exam StructureCompared to the previous year, the structure of the USE has not changed significantly. 235 minutes are allotted for the entire work. Each task of the basic part should be solved from 1 to 5 minutes. Tasks of increased complexity are solved in about 5-10 minutes. All CIMs are stored at the exam venue and will be opened during the test. The structure is as follows: 27 basic tasks test the knowledge of the examinee in all areas of physics, from mechanics to quantum and nuclear physics. In 5 tasks of a high level of complexity, the student shows skills in the logical justification of his decision and the correctness of the train of thought. The number of primary points can reach a maximum of 52. Then they are recalculated within the framework of a 100-point scale. Due to the change in the primary score, the minimum passing score may also change. Demo versionThe demo version of the exam in physics is already on the official fipi portal, which is developing a unified state exam. The structure and complexity of the demo version is similar to the one that will appear on the exam. Each task is described in detail, at the end there is a list of answers to questions on which the student checks his decisions. Also at the end is a detailed layout for each of the five tasks, indicating the number of points for correctly or partially completed actions. For each task of high complexity, you can get from 2 to 4 points, depending on the requirements and the deployment of the solution. Tasks can contain a sequence of numbers that you need to write down correctly, establishing a correspondence between elements, as well as small tasks in one or two actions.
We wish you to successfully pass physics and enter the desired university, everything is in your hands! Secondary general education Getting ready for the Unified State Exam-2018: analysis of the demo version in physicsWe bring to your attention an analysis of the tasks of the exam in physics from the demo version of 2018. The article contains explanations and detailed algorithms for solving tasks, as well as recommendations and links to useful materials that are relevant in preparing for the exam.
USE-2018. Physics. Thematic training tasks The edition contains: A point body at rest begins to move along the axis Ox. The figure shows a projection dependency graph ax acceleration of this body with time t. Determine the distance traveled by the body in the third second of motion. Answer: _________ m. SolutionBeing able to read graphs is very important for every student. The question in the problem is that it is required to determine from the graph the dependence of the projection of acceleration on time, the path that the body has traveled in the third second of motion. The graph shows that in the time interval from t 1 = 2 s to t 2 = 4 s, acceleration projection is zero. Consequently, the projection of the resultant force in this area, according to Newton's second law, is also equal to zero. We determine the nature of the movement in this area: the body moved uniformly. The path is easy to determine, knowing the speed and time of movement. However, in the interval from 0 to 2 s, the body moved uniformly accelerated. Using the definition of acceleration, we write the velocity projection equation Vx = V 0x + a x t; since the body was initially at rest, then the velocity projection by the end of the second second became Then the path traveled by the body in the third second Answer: 8 m Rice. 1 On a smooth horizontal surface lie two bars connected by a light spring. To a bar of mass m= 2 kg apply a constant force equal in modulus F= 10 N and directed horizontally along the axis of the spring (see figure). Determine the modulus of the elastic force of the spring at the moment when this bar moves with an acceleration of 1 m / s 2. Answer: _________ N. SolutionHorizontally on a body of mass m\u003d 2 kg, two forces act, this is the force F= 10 N and elastic force, from the side of the spring. The resultant of these forces imparts acceleration to the body. We choose a coordinate line and direct it along the action of the force F. Let's write down Newton's second law for this body. Projected onto axis 0 X: F – F extr = ma (2) We express from formula (2) the modulus of the elastic force F extr = F – ma (3) Substitute the numerical values into formula (3) and get, F control \u003d 10 N - 2 kg 1 m / s 2 \u003d 8 N. Answer: 8 N. Task 3A body with a mass of 4 kg, located on a rough horizontal plane, was reported along it with a speed of 10 m / s. Determine the modulus of work done by the friction force from the moment the body begins to move until the moment when the speed of the body decreases by 2 times. Answer: _________ J. SolutionThe force of gravity acts on the body, the reaction force of the support is the friction force that creates a braking acceleration. The body was initially reported with a speed equal to 10 m / s. Let's write down Newton's second law for our case. Equation (1) taking into account the projection on the selected axis Y will look like: N – mg = 0; N = mg (2) In the projection on the axis X: –F tr = - ma; F tr = ma; (3) We need to determine the modulus of work of the friction force by the time when the speed becomes half as much, i.e. 5 m/s. Let's write a formula for calculating work. A · ( F tr) = – F tr S (4) To determine the distance traveled, we take the timeless formula:
Substitute (3) and (5) into (4) Then the modulus of work of the friction force will be equal to: Let's substitute numerical values
Answer: 150 J USE-2018. Physics. 30 practice exam papers The edition contains: The stepped block has an outer pulley with a radius of 24 cm. Weights are suspended from the threads wound on the outer and inner pulleys as shown in the figure. There is no friction in the axis of the block. What is the radius of the inner pulley of the block if the system is in equilibrium? Rice. one Answer: _________ see SolutionAccording to the condition of the problem, the system is in equilibrium. On the image L 1 , shoulder strength L 2 shoulder of force Balance condition: the moments of forces rotating the bodies clockwise must be equal to the moments of forces rotating the body counterclockwise. Recall that the moment of force is the product of the modulus of force and the arm. The forces acting on the threads from the side of the loads differ by a factor of 3. This means that the radius of the inner pulley of the block differs from the outer one also by 3 times. Therefore, the shoulder L 2 will be equal to 8 cm. Answer: 8 cm Task 5Oh, at different times. Select from the list below two correct statements and indicate their numbers.
SolutionThe table shows data on the position of a ball attached to a spring and oscillating along a horizontal axis. Oh, at different times. We need to analyze this data and choose the right two statements. The system is a spring pendulum. At the point in time t\u003d 1 s, the displacement of the body from the equilibrium position is maximum, which means this is the amplitude value. by definition, the potential energy of an elastically deformed body can be calculated by the formula
where k- coefficient of spring stiffness, X- displacement of the body from the equilibrium position. If the displacement is maximum, then the speed at this point is zero, which means that the kinetic energy will be zero. According to the law of conservation and transformation of energy, potential energy should be maximum. From the table we see that the body passes half of the oscillation for t= 2 s, total oscillation in twice the time T= 4 s. Therefore statements 1 will be true; 2. Task 6A small piece of ice was lowered into a cylindrical glass of water to float. After some time, the ice completely melted. Determine how the pressure on the bottom of the glass and the water level in the glass have changed as a result of the melting of the ice.
Write to table Solution
Problems of this type are quite common in different versions of the exam. And as practice shows, students often make mistakes. Let's try to analyze this task in detail. Denote m is the mass of a piece of ice, ρ l is the density of ice, ρ w is the density of water, V pt is the volume of the immersed part of the ice, equal to the volume of the displaced liquid (volume of the hole). Mentally remove the ice from the water. Then a hole will remain in the water, the volume of which is equal to V pm, i.e. volume of water displaced by a piece of ice one( b). Let us write down the condition of ice floating Fig. one( a). Fa = mg (1) ρ in V pm g = mg (2) Comparing formulas (3) and (4) we see that the volume of the hole is exactly equal to the volume of water obtained from the melting of our piece of ice. Therefore, if we now (mentally) pour the water obtained from ice into the hole, then the hole will be completely filled with water, and the water level in the vessel will not change. If the water level does not change, then the hydrostatic pressure (5), which in this case depends only on the height of the liquid, will also not change. Therefore, the answer will be USE-2018. Physics. Training tasks The publication is addressed to high school students to prepare for the exam in physics. A weightless spring is located on a smooth horizontal surface and is attached to the wall at one end (see figure). At some point in time, the spring begins to deform, applying an external force to its free end A and uniformly moving point A. Establish a correspondence between the graphs of dependences of physical quantities on deformation x springs and these values. For each position in the first column, select the corresponding position from the second column and write in table SolutionIt can be seen from the figure for the problem that when the spring is not deformed, then its free end, and accordingly point A, are in a position with the coordinate X 0 . At some point in time, the spring begins to deform, applying an external force to its free end A. Point A moves uniformly. Depending on whether the spring is stretched or compressed, the direction and magnitude of the elastic force arising in the spring will change. Accordingly, under the letter A), the graph is the dependence of the elastic modulus on the deformation of the spring. The graph under the letter B) is the dependence of the projection of the external force on the magnitude of the deformation. Because with an increase in the external force, the magnitude of the deformation and the elastic force increase. Answer: 24. Task 8When constructing the Réaumur temperature scale, it is assumed that at normal atmospheric pressure, ice melts at a temperature of 0 degrees Réaumur (°R), and water boils at a temperature of 80°R. Find the average kinetic energy of the translational thermal motion of an ideal gas particle at a temperature of 29°R. Express your answer in eV and round to the nearest hundredth. Answer: _______ eV. SolutionThe problem is interesting in that it is necessary to compare two temperature measurement scales. These are the Réaumur temperature scale and the Celsius temperature scale. The melting points of ice are the same on the scales, but the boiling points are different, we can get a formula for converting degrees Réaumur to degrees Celsius. it Let's convert the temperature of 29 (°R) to degrees Celsius We translate the result into Kelvin using the formula T = t°C + 273 (2); T= 36.25 + 273 = 309.25 (K) To calculate the average kinetic energy of the translational thermal motion of particles of an ideal gas, we use the formula where k– Boltzmann constant equal to 1.38 10 –23 J/K, T is the absolute temperature on the Kelvin scale. It can be seen from the formula that the dependence of the average kinetic energy on temperature is direct, that is, how many times the temperature changes, the average kinetic energy of the thermal motion of molecules changes so many times. Substitute the numerical values: The result is converted to electron volts and rounded to the nearest hundredth. Let's remember that 1 eV \u003d 1.6 10 -19 J. For this Answer: 0.04 eV. One mole of a monatomic ideal gas is involved in process 1–2, the graph of which is shown in VT-diagram. Determine for this process the ratio of the change in the internal energy of the gas to the amount of heat imparted to the gas. Answer: ___________ . SolutionAccording to the condition of the problem in process 1–2, the graph of which is shown in VT-diagram, one mole of a monatomic ideal gas is involved. To answer the question of the problem, it is necessary to obtain expressions for changing the internal energy and the amount of heat imparted to the gas. Isobaric process (Gay-Lussac law). The change in internal energy can be written in two forms: For the amount of heat imparted to the gas, we write the first law of thermodynamics: Q 12 = A 12+∆ U 12 (5), where A 12 - gas work during expansion. By definition, work is A 12 = P 0 2 V 0 (6). Then the amount of heat will be equal, taking into account (4) and (6). Q 12 = P 0 2 V 0 + 3P 0 · V 0 = 5P 0 · V 0 (7) Let's write the relation: Answer: 0,6.
The reference book contains in full the theoretical material on the course of physics, which is necessary for passing the exam. The structure of the book corresponds to the modern codifier of content elements in the subject, on the basis of which the examination tasks are compiled - control and measuring materials (CMM) of the Unified State Examination. The theoretical material is presented in a concise, accessible form. Each topic is accompanied by examples of exam tasks corresponding to the USE format. This will help the teacher to organize preparation for the unified state exam, and students to independently test their knowledge and readiness for the final exam. A blacksmith forges an iron horseshoe weighing 500 g at a temperature of 1000°C. Having finished forging, he throws the horseshoe into a vessel of water. There is a hiss, and steam rises from the vessel. Find the mass of water that evaporates when a hot horseshoe is immersed in it. Consider that the water is already heated to boiling point. Answer: _________ SolutionTo solve the problem, it is important to remember the heat balance equation. If there are no losses, then heat transfer of energy occurs in the system of bodies. As a result, the water evaporates. Initially, the water was at a temperature of 100 ° C, which means that after the hot horseshoe is immersed, the energy received by the water will go immediately to vaporization. We write the heat balance equation With and · m P · ( t n - 100) = lm in 1), where L is the specific heat of vaporization, m c is the mass of water that has turned into steam, m p is the mass of the iron horseshoe, With g is the specific heat capacity of iron. From formula (1) we express the mass of water When recording the answer, pay attention to what units you want to leave the mass of water. Answer: 90 One mole of a monatomic ideal gas is involved in a cyclic process, the graph of which is shown in TV- chart. Select two correct statements based on the analysis of the presented graph.
SolutionThis type of task tests the ability to read graphs and explain the presented dependence of physical quantities. It is important to remember how dependency graphs look for isoprocesses in different axes, in particular R= const. In our example on TV The diagram shows two isobars. Let's see how the pressure and volume will change at a fixed temperature. For example, for points 1 and 4 lying on two isobars. P 1 . V 1 = P 4 . V 4 , we see that V 4 > V 1 means P 1 > P four . State 2 corresponds to pressure P one . Consequently, the gas pressure in state 2 is greater than the gas pressure in state 4. In section 2–3, the process is isochoric, the gas does no work, it is equal to zero. The assertion is incorrect. In section 1-2, the pressure increases, also incorrect. Just above we showed that this is an isobaric transition. In section 4–1, a certain amount of heat is removed from the gas in order to maintain the temperature constant when the gas is compressed. Answer: 14. The heat engine works according to the Carnot cycle. The temperature of the refrigerator of the heat engine was increased, leaving the temperature of the heater the same. The amount of heat received by the gas from the heater per cycle has not changed. How did the efficiency of the heat engine and the work of the gas per cycle change? For each value, determine the appropriate nature of the change:
Write to table selected figures for each physical quantity. Numbers in the answer may be repeated. SolutionHeat engines operating on the Carnot cycle are often found in assignments on the exam. First of all, you need to remember the formula for calculating the efficiency factor. Be able to record it through the temperature of the heater and the temperature of the refrigerator in addition to be able to write the efficiency through the useful work of the gas A g and the amount of heat received from the heater Q n. We carefully read the condition and determined which parameters were changed: in our case, we increased the temperature of the refrigerator, leaving the temperature of the heater the same. Analyzing formula (1), we conclude that the numerator of the fraction decreases, the denominator does not change, therefore, the efficiency of the heat engine decreases. If we work with formula (2), we will immediately answer the second question of the problem. The work of the gas per cycle will also decrease, with all the current changes in the parameters of the heat engine. Answer: 22. negative charge - qQ and negative- Q(see picture). Where is it directed relative to the picture ( right, left, up, down, towards the observer, away from the observer) charge acceleration - q in this moment of time, if only charges act on it + Q and –Q? Write your answer in word(s) SolutionRice. one negative charge - q is in the field of two fixed charges: positive + Q and negative- Q, as shown in the figure. in order to answer the question of where the acceleration of the charge is directed - q, at the moment when only +Q and - charges act on it Q it is necessary to find the direction of the resulting force, as a geometric sum of forces According to Newton's second law, it is known that the direction of the acceleration vector coincides with the direction of the resulting force. The figure shows a geometric construction to determine the sum of two vectors. The question arises why the forces are directed in this way? Recall how similarly charged bodies interact, they repel each other, the Coulomb force of the interaction of charges is the central force. the force with which oppositely charged bodies attract. From the figure, we see that the charge is q equidistant from fixed charges whose moduli are equal. Therefore, modulo will also be equal. The resulting force will be directed relative to the figure way down. Charge acceleration will also be directed - q, i.e. way down. Answer: Way down.
The book contains materials for the successful passing of the exam in physics: brief theoretical information on all topics, tasks of different types and levels of complexity, solving problems of an increased level of complexity, answers and evaluation criteria. Students do not have to search for additional information on the Internet and buy other manuals. In this book, they will find everything they need to independently and effectively prepare for the exam. The publication contains tasks of different types on all topics tested at the exam in physics, as well as solving problems of an increased level of complexity. The publication will provide invaluable assistance to students in preparing for the exam in physics, and can also be used by teachers in organizing the educational process. Two resistors connected in series with a resistance of 4 ohms and 8 ohms are connected to a battery, the voltage at the terminals of which is 24 V. What thermal power is released in a resistor of a smaller rating? Answer: _________ Tue. SolutionTo solve the problem, it is desirable to draw a series connection diagram of resistors. Then remember the laws of the series connection of conductors. The scheme will be as follows: Where R 1 = 4 ohm, R 2 = 8 ohms. The voltage at the battery terminals is 24 V. When the conductors are connected in series, the current strength will be the same in each section of the circuit. The total resistance is defined as the sum of the resistances of all resistors. According to Ohm's law for the circuit section we have: To determine the thermal power released on a resistor of a smaller rating, we write: P = I 2 R\u003d (2 A) 2 4 Ohm \u003d 16 W. Answer: P= 16 W. A wire frame with an area of 2 · 10–3 m 2 rotates in a uniform magnetic field around an axis perpendicular to the magnetic induction vector. The magnetic flux penetrating the frame area changes according to the law Ф = 4 10 –6 cos10π t, where all quantities are expressed in SI. What is the modulus of magnetic induction? Answer: ________________ mT. SolutionThe magnetic flux changes according to the law Ф = 4 10 –6 cos10π t, where all quantities are expressed in SI. You need to understand what magnetic flux is in general and how this value is related to the magnetic induction modulus B and frame area S. Let's write the equation in general form to understand what quantities are included in it. Φ = Φ m cosω t(1) Remember that before the cos or sin sign there is an amplitude value of a changing value, which means Φ max \u003d 4 10 -6 Wb, on the other hand, the magnetic flux is equal to the product of the magnetic induction modulus and the circuit area and the cosine of the angle between the normal to the circuit and the magnetic induction vector Φ m = AT · S cosα, the flux is maximum at cosα = 1; express the modulus of induction The answer must be written in mT. Our result is 2 mT. Answer: 2. The section of the electrical circuit is a series-connected silver and aluminum wires. A constant electric current of 2 A flows through them. The graph shows how the potential φ changes in this section of the circuit when it is displaced along the wires by a distance x Using the graph, select two correct statements and indicate their numbers in the answer.
SolutionThe answer to the question in the problem will be two correct statements. To do this, let's try to solve a few simple problems using a graph and some data. The section of the electrical circuit is a series-connected silver and aluminum wires. A constant electric current of 2 A flows through them. The graph shows how the potential φ changes in this section of the circuit when it is displaced along the wires by a distance x. The specific resistances of silver and aluminum are 0.016 μΩ m and 0.028 μΩ m, respectively. The wires are connected in series, therefore, the current strength in each section of the circuit will be the same. The electrical resistance of the conductor depends on the material from which the conductor is made, the length of the conductor, the cross-sectional area of \u200b\u200bthe wire
where ρ is the resistivity of the conductor; l- conductor length; S- cross-sectional area. It can be seen from the graph that the length of the silver wire L c = 8 m; aluminum wire length L a \u003d 14 m. Voltage on the section of silver wire U c \u003d Δφ \u003d 6 V - 2 V \u003d 4 V. Voltage in the section of aluminum wire U a \u003d Δφ \u003d 2 V - 1 V \u003d 1 V. According to the condition, it is known that a constant electric current of 2 A flows through the wires, knowing the voltage and current strength, we determine the electrical resistance according to Ohm's law for the circuit section. It is important to note that the numerical values must be in the SI system for calculations. Correct statement 2. Let's check the expressions for power. P a = I 2 · R a(4); P a \u003d (2 A) 2 0.5 Ohm \u003d 2 W.
The reference book contains in full the theoretical material on the course of physics, which is necessary for passing the exam. The structure of the book corresponds to the modern codifier of content elements in the subject, on the basis of which the examination tasks are compiled - control and measuring materials (CMM) of the Unified State Examination. The theoretical material is presented in a concise, accessible form. Each topic is accompanied by examples of exam tasks corresponding to the USE format. This will help the teacher to organize preparation for the unified state exam, and students to independently test their knowledge and readiness for the final exam. At the end of the manual, answers are given to tasks for self-examination, which will help schoolchildren and applicants to objectively assess the level of their knowledge and the degree of preparedness for the certification exam. The manual is addressed to senior students, applicants and teachers. A small object is located on the main optical axis of a thin converging lens between the focal length and twice the focal length from it. The object is brought closer to the focus of the lens. How does this change the image size and optical power of the lens? For each quantity, determine the appropriate nature of its change:
Write to table selected figures for each physical quantity. Numbers in the answer may be repeated. SolutionThe object is located on the main optical axis of a thin converging lens between the focal and double focal lengths from it. The object begins to be brought closer to the focus of the lens, while the optical power of the lens does not change, since we do not change the lens.
where F is the focal length of the lens; D is the optical power of the lens. To answer the question of how the image size will change, it is necessary to build an image for each position. Rice. 1 Rice. 2 We built two images for two positions of the subject. It is obvious that the size of the second image has increased. Answer: 13. The figure shows a DC circuit. The internal resistance of the current source can be neglected. Establish a correspondence between physical quantities and formulas by which they can be calculated ( - EMF of the current source; R is the resistance of the resistor). For each position of the first column, select the corresponding position of the second and write in table selected numbers under the corresponding letters. |
ν cr = | A exit | (7), |
h |
this is the minimum frequency at which the photoelectric effect is still possible. The dependence of the maximum kinetic energy of photoelectrons on the frequency of the incident light is reflected in the graph under the letter B).
Answer: |
||
Determine the ammeter readings (see figure) if the error in direct measurement of the current strength is equal to the division value of the ammeter.
Answer: (____________________±___________) A.
Solution
The task tests the ability to record the readings of the measuring device, taking into account the specified measurement error. Let's determine the scale division value With\u003d (0.4 A - 0.2 A) / 10 \u003d 0.02 A. The measurement error according to the condition is equal to the scale division, i.e. Δ I = c= 0.02 A. We write the final result as:
I= (0.20 ± 0.02) A
It is necessary to assemble an experimental setup with which you can determine the coefficient of sliding friction of steel on wood. To do this, the student took a steel bar with a hook. Which two items from the list of equipment below should be additionally used to conduct this experiment?
- wooden lath
- dynamometer
- beaker
- plastic rail
- stopwatch
In response, write down the numbers of the selected items.
Solution
In the task, it is required to determine the coefficient of sliding friction of steel on wood, therefore, to conduct an experiment, it is necessary to take a wooden ruler and a dynamometer from the proposed list of equipment to measure force. It is useful to recall the formula for calculating the modulus of sliding friction force
fck = μ · N (1),
where μ is the coefficient of sliding friction, N is the reaction force of the support, equal in modulus to the weight of the body.
Answer: |
The handbook contains detailed theoretical material on all topics tested by the USE in physics. After each section, multi-level tasks are given in the form of the exam. For the final control of knowledge at the end of the handbook, training options are given that correspond to the exam. Students do not have to search for additional information on the Internet and buy other manuals. In this guide, they will find everything they need to independently and effectively prepare for the exam. The reference book is addressed to high school students to prepare for the exam in physics. The manual contains detailed theoretical material on all topics tested by the exam. After each section, examples of USE tasks and a practice test are given. All questions are answered. The publication will be useful to teachers of physics, parents for the effective preparation of students for the exam.
Consider a table containing information about bright stars.
Star name |
Temperature, |
Weight |
Radius |
Distance to the star |
Aldebaran |
5 |
|||
Betelgeuse |
||||
Select two statements that match the characteristics of the stars.
- The surface temperature and radius of Betelgeuse indicate that this star belongs to the red supergiants.
- The temperature on the surface of Procyon is 2 times lower than on the surface of the Sun.
- The stars Castor and Capella are at the same distance from the Earth and, therefore, belong to the same constellation.
- The star Vega belongs to the white stars of spectral class A.
- Since the masses of the Vega and Capella stars are the same, they belong to the same spectral type.
Solution
Star name |
Temperature, |
Weight |
Radius |
Distance to the star |
Aldebaran |
||||
Betelgeuse |
||||
2,5 |
||||
In the task, you need to choose two true statements that correspond to the characteristics of the stars. The table shows that Betelgeuse has the lowest temperature and the largest radius, which means that this star belongs to red giants. Therefore, the correct answer is (1). To correctly choose the second statement, it is necessary to know the distribution of stars by spectral types. We need to know the temperature interval and the color of the star corresponding to this temperature. Analyzing the table data, we conclude that (4) will be the correct statement. The star Vega belongs to the white stars of spectral class A.
A 2 kg projectile flying at a speed of 200 m/s breaks into two fragments. The first fragment of mass 1 kg flies at an angle of 90° to the original direction with a speed of 300 m/s. Find the speed of the second fragment.
Answer: _______ m/s.
Solution
At the moment of projectile burst (Δ t→ 0), the effect of gravity can be neglected and the projectile can be considered as a closed system. According to the law of conservation of momentum: the vector sum of the momenta of the bodies included in a closed system remains constant for any interactions of the bodies of this system with each other. for our case we write:
- projectile speed; m- the mass of the projectile before rupture; is the speed of the first fragment; m 1 is the mass of the first fragment; m 2 – mass of the second fragment; is the speed of the second fragment.
Let's choose the positive direction of the axis X, coinciding with the direction of the projectile velocity, then in the projection onto this axis we write equation (1):
mv x = m 1 v 1x + m 2 v 2x (2)
According to the condition, the first fragment flies at an angle of 90° to the original direction. The length of the desired momentum vector is determined by the Pythagorean theorem for a right triangle.
p 2 = √p 2 + p 1 2 (3)
p 2 = √400 2 + 300 2 = 500 (kg m/s)
Answer: 500 m/s.
When compressing an ideal monatomic gas at constant pressure, external forces did 2000 J of work. How much heat was transferred by the gas to the surrounding bodies?
Answer: _____ J.
Solution
A challenge to the first law of thermodynamics.
Δ U = Q + A sun, (1)
Where Δ U – change in the internal energy of the gas, Q- the amount of heat transferred by the gas to the surrounding bodies, A Sun is the work of external forces. According to the condition, the gas is monatomic and it is compressed at a constant pressure.
A sun = - A g(2),
Q = Δ U– A sun = Δ U+ A r = | 3 | pΔ V + pΔ V = | 5 | pΔ V, |
2 | 2 |
where pΔ V = A G
Answer: 5000 J
A plane monochromatic light wave with a frequency of 8.0 · 10 14 Hz is incident along the normal onto a diffraction grating. A converging lens with a focal length of 21 cm is placed parallel to the grating behind it. The diffraction pattern is observed on the screen in the rear focal plane of the lens. The distance between its main maxima of the 1st and 2nd orders is 18 mm. Find the lattice period. Express your answer in micrometers (µm) rounded to the nearest tenth. Calculate for small angles (φ ≈ 1 in radians) tgα ≈ sinφ ≈ φ.
Solution
The angular directions to the maxima of the diffraction pattern are determined by the equation
d sinφ = kλ (1),
where d is the period of the diffraction grating, φ is the angle between the normal to the grating and the direction to one of the maxima of the diffraction pattern, λ is the light wavelength, k is an integer called the order of the diffraction maximum. Let us express from equation (1) the period of the diffraction grating
Rice. one
According to the condition of the problem, we know the distance between its main maxima of the 1st and 2nd order, we denote it as Δ x\u003d 18 mm \u003d 1.8 10 -2 m, light wave frequency ν \u003d 8.0 10 14 Hz, focal length of the lens F\u003d 21 cm \u003d 2.1 10 -1 m. We need to determine the period of the diffraction grating. On fig. 1 shows a diagram of the path of rays through the grating and the lens behind it. On the screen, located in the focal plane of the converging lens, a diffraction pattern is observed as a result of the interference of waves coming from all the slits. We use formula one for two maxima of the 1st and 2nd order.
d sinφ 1 = kλ(2),
if k = 1, then d sinφ 1 = λ (3),
write similarly for k = 2,
Since the angle φ is small, tgφ ≈ sinφ. Then from Fig. 1 we see that
where x 1 is the distance from the zero maximum to the maximum of the first order. Similarly for the distance x 2 .
Then we have
grating period,
because by definition
where With\u003d 3 10 8 m / s - the speed of light, then substituting the numerical values we get
The answer was presented in micrometers, rounded to tenths, as required in the problem statement.
Answer: 4.4 µm.
Based on the laws of physics, find the reading of an ideal voltmeter in the circuit shown in the figure, before closing the key to and describe the changes in its readings after closing the key K. Initially, the capacitor is not charged.
Solution
Rice. one
The tasks in Part C require the student to provide a full and detailed answer. Based on the laws of physics, it is necessary to determine the readings of the voltmeter before closing the key K and after closing the key K. Let us take into account that initially the capacitor in the circuit is not charged. Let's consider two states. When the key is open, only the resistor is connected to the power supply. The voltmeter reading is zero, since it is connected in parallel with the capacitor, and the capacitor is not initially charged, then q 1 = 0. The second state is when the key is closed. Then the readings of the voltmeter will increase until they reach the maximum value, which will not change with time,
where r is the internal resistance of the source. Voltage across the capacitor and resistor, according to Ohm's law for the circuit section U = I · R will not change over time, and the voltmeter readings will stop changing.
A wooden ball is tied with a thread to the bottom of a cylindrical vessel with a bottom area S\u003d 100 cm 2. Water is poured into the vessel so that the ball is completely immersed in the liquid, while the thread is stretched and acts on the ball with a force T. If the thread is cut, the ball will float and the water level will change to h \u003d 5 cm. Find the tension in the thread T.
Solution
Rice. one |
Rice. 2 |
Initially, a wooden ball is tied with a thread to the bottom of a cylindrical vessel with a bottom area S\u003d 100 cm 2 \u003d 0.01 m 2 and completely immersed in water. Three forces act on the ball: the force of gravity from the side of the Earth, - the force of Archimedes from the side of the liquid, - the force of the tension of the thread, the result of the interaction of the ball and the thread. According to the balance condition of the ball in the first case, the geometric sum of all forces acting on the ball must be equal to zero:
Let's choose the coordinate axis OY and point it up. Then, taking into account the projection, equation (1) can be written:
Fa 1 = T + mg (2).
Let's write the force of Archimedes:
Fa 1 = ρ V 1 g (3),
where V 1 - the volume of the part of the ball immersed in water, in the first it is the volume of the entire ball, m is the mass of the ball, ρ is the density of water. The equilibrium condition in the second case
Fa 2 = mg(4)
Let's write out the force of Archimedes in this case:
Fa 2 = ρ V 2 g (5),
where V 2 is the volume of the part of the sphere immersed in the liquid in the second case.
Let's work with equations (2) and (4) . You can use the substitution method or subtract from (2) - (4), then Fa 1 – Fa 2 = T, using formulas (3) and (5) we obtain ρ · V 1 g– ρ · V 2 g= T;
ρg ( V 1 – V 2) = T (6)
Given that
V 1 – V 2 = S · h (7),
where h= H 1 - H 2; we get
T= ρ g S · h (8)
Let's substitute numerical values
Answer: 5 N.
All the information necessary for passing the exam in physics is presented in visual and accessible tables, after each topic there are training tasks for knowledge control. With the help of this book, students will be able to improve their knowledge in the shortest possible time, remember all the most important topics in a matter of days before the exam, practice completing assignments in the USE format and become more confident in their abilities. After repeating all the topics presented in the manual, the long-awaited 100 points will be much closer! The manual contains theoretical information on all topics tested at the exam in physics. After each section, training tasks of different types with answers are given. A visual and accessible presentation of the material will allow you to quickly find the information you need, eliminate gaps in knowledge and repeat a large amount of information in the shortest possible time. The publication will assist high school students in preparing for lessons, various forms of current and intermediate control, as well as preparing for exams.
Task 30
In a room with dimensions of 4 × 5 × 3 m, in which the air has a temperature of 10 ° C and a relative humidity of 30%, a humidifier with a capacity of 0.2 l / h was turned on. What will be the relative humidity of the air in the room after 1.5 hours? Saturated water vapor pressure at 10 °C is 1.23 kPa. Consider the room as a hermetic vessel.
Solution
When starting to solve problems for vapors and humidity, it is always useful to keep in mind the following: if the temperature and pressure (density) of the saturating vapor are given, then its density (pressure) is determined from the Mendeleev-Clapeyron equation. Write down the Mendeleev-Clapeyron equation and the relative humidity formula for each state.
For the first case at φ 1 = 30%. The partial pressure of water vapor is expressed from the formula:
where T = t+ 273 (K), R is the universal gas constant. We express the initial mass of the vapor contained in the room using equations (2) and (3):
During the time τ of the humidifier operation, the mass of water will increase by
Δ m = τ · ρ · I, (6)
where I– performance of the humidifier according to the condition, it is equal to 0.2 l / h = 0.2 10 -3 m 3 / h, ρ = 1000 kg / m 3 - the density of water. Substitute formulas (4) and (5) in (6)
We transform the expression and express
This is the desired formula for the relative humidity that will be in the room after the operation of the humidifier.
Substitute the numerical values and get the following result
Answer: 83 %.
On horizontally arranged rough rails with negligible resistance, two identical rods of mass m= 100 g and resistance R= 0.1 ohm each. The distance between the rails is l = 10 cm, and the coefficient of friction between the rods and the rails is μ = 0.1. Rails with rods are in a uniform vertical magnetic field with induction B = 1 T (see figure). Under the action of a horizontal force acting on the first rod along the rail, both rods move translationally uniformly at different speeds. What is the speed of the first rod relative to the second? Ignore the self-inductance of the circuit.
Solution
Rice. one
The task is complicated by the fact that two rods are moving and it is necessary to determine the speed of the first relative to the second. Otherwise, the approach to solving problems of this type remains the same. A change in the magnetic flux penetrating the circuit leads to the emergence of an EMF of induction. In our case, when the rods move at different speeds, the change in the flux of the magnetic induction vector penetrating the circuit over the time interval Δ t is determined by the formula
ΔΦ = B · l · ( v 1 – v 2) Δ t (1)
This leads to the appearance of an EMF of induction. According to Faraday's law
By the condition of the problem, we neglect the self-induction of the circuit. According to Ohm's law for a closed circuit for the current that occurs in the circuit, we write the expression:
Current-carrying conductors in a magnetic field are affected by the Ampere force and the modules of which are equal to each other, and are equal to the product of the current strength, the module of the magnetic induction vector and the length of the conductor. Since the force vector is perpendicular to the direction of the current, then sinα = 1, then
F 1 = F 2 = I · B · l (4)
The braking force of friction still acts on the rods,
F tr = μ m · g (5)
by condition it is said that the rods move uniformly, which means that the geometric sum of the forces applied to each rod is equal to zero. Only the Ampere force and the friction force act on the second rod. Therefore, F tr = F 2 , taking into account (3), (4), (5)
Let us express from here the relative speed
Substitute the numerical values:
Answer: 2 m/s.
In an experiment to study the photoelectric effect, light with a frequency of ν = 6.1 · 10 14 Hz falls on the cathode surface, as a result of which a current appears in the circuit. Current dependency graph I from voltage U between the anode and cathode is shown in the figure. What is the power of the incident light R, if on average one out of 20 photons incident on the cathode knocks out an electron?
Solution
By definition, the current strength is a physical quantity numerically equal to the charge q passing through the cross section of the conductor per unit time t:
I = | q | (1). |
t |
If all the photoelectrons knocked out of the cathode reach the anode, then the current in the circuit reaches saturation. The total charge passing through the cross section of the conductor can be calculated
q = N e · e · t (2),
where e is the electron charge modulus, N e– the number of photoelectrons knocked out of the cathode in 1 s. According to the condition, one out of 20 photons incident on the cathode knocks out an electron. Then
where N f is the number of photons incident on the cathode in 1 s. The maximum current in this case will be
Our task is to find the number of photons incident on the cathode. It is known that the energy of one photon is equal to E f = h · v, then the power of the incident light
After substituting the corresponding quantities, we obtain the final formula
P = N f · h · v = | twenty · I max h USE-2018. Physics (60x84/8) 10 practice exam papers to prepare for the unified state exam The attention of schoolchildren and applicants is offered a new manual in physics for the preparation of the Unified State Examination, which contains 10 options for training examination papers. Each option is compiled in full accordance with the requirements of the unified state exam in physics, includes tasks of different types and levels of complexity. At the end of the book, answers are given for self-examination of all tasks. The proposed training options will help the teacher to organize preparation for the unified state exam, and students to independently test their knowledge and readiness for the final exam. The manual is addressed to schoolchildren, applicants and teachers. |
Secondary general education
Line UMK G. Ya. Myakishev, M.A. Petrova. Physics (10-11) (B)
USE-2020 codifier in physics FIPI
The codifier of content elements and requirements for the level of training of graduates of educational organizations for the USE in physics is one of the documents that determine the structure and content of the KIM of the unified state exam, the list objects of which have a specific code. A codifier was compiled on the basis of the Federal component of state standards for basic general and secondary (complete) general education in physics (basic and profile levels).Key changes in the new demo
For the most part, the changes were minor. So, in tasks in physics there will be not five, but six questions, implying a detailed answer. Task No. 24 on knowledge of the elements of astrophysics has become more complicated - now, instead of two mandatory correct answers, there can be either two or three correct options.
Soon we will talk about the upcoming exam on and on the air our YouTube channel.
USE schedule in physics in 2020
At the moment, it is known that the Ministry of Education and Rosobrnadzor have published draft USE schedules for public discussion. Physics exams are scheduled to be held on June 4th.
The codifier is information divided into two parts:
part 1: "List of content elements checked at the unified state exam in physics";
part 2: "List of requirements for the level of graduates' preparation, checked at the unified state exam in physics."
List of content elements tested at the unified state exam in physics
We present the original table with a list of content elements provided by FIPI. You can download the USE codifier in physics in the full version at official website.
Section code | Controlled element code | Content elements verified by CMM tasks |
1 | Mechanics |
|
1.1 | Kinematics |
|
1.2 | Dynamics |
|
1.3 | Statics |
|
1.4 | Conservation laws in mechanics |
|
1.5 | Mechanical vibrations and waves |
|
2 | Molecular physics. Thermodynamics |
|
2.1 | Molecular physics |
|
2.2 | Thermodynamics |
|
3 | Electrodynamics |
|
3.1 | Electric field |
|
3.2 | DC Laws |
|
3.3 | A magnetic field |
|
3.4 | Electromagnetic induction |
|
3.5 | Electromagnetic oscillations and waves |
|
3.6 | Optics |
|
4 | Fundamentals of special relativity |
|
5 | Quantum physics and elements of astrophysics |
|
5.1 | Wave-particle duality |
|
5.2 | Physics of the atom |
|
5.3 | Physics of the atomic nucleus |
|
5.4 | Elements of astrophysics |
|
The book contains materials for the successful passing of the exam: brief theoretical information on all topics, tasks of different types and levels of complexity, solving problems of an increased level of complexity, answers and evaluation criteria. Students do not have to search for additional information on the Internet and buy other manuals. In this book, they will find everything they need to independently and effectively prepare for the exam.
Requirements for the level of training of graduates
KIM FIPI are developed based on specific requirements for the level of preparation of examinees. Thus, in order to successfully cope with the physics exam, the graduate must:
1. Know/understand:
1.1. the meaning of physical concepts;
1.2. the meaning of physical quantities;
1.3. the meaning of physical laws, principles, postulates.
2. Be able to:
2.1. describe and explain:
2.1.1. physical phenomena, physical phenomena and properties of bodies;
2.1.2. experimental results;
2.2. describe fundamental experiments that have had a significant impact on the development of physics;
2.3. give examples of the practical application of physical knowledge, the laws of physics;
2.4. determine the nature of the physical process according to the schedule, table, formula; products of nuclear reactions based on the laws of conservation of electric charge and mass number;
2.5.1. distinguish hypotheses from scientific theories; draw conclusions based on experimental data; give examples showing that: observations and experiments are the basis for putting forward hypotheses and theories and allow you to verify the truth of theoretical conclusions, physical theory makes it possible to explain known natural phenomena and scientific facts, predict still unknown phenomena;
2.5.2. give examples of experiments illustrating that: observations and experiment serve as the basis for hypotheses and the construction of scientific theories; experiment allows you to check the truth of theoretical conclusions; physical theory makes it possible to explain natural phenomena and scientific facts; physical theory makes it possible to predict still unknown phenomena and their features; when explaining natural phenomena, physical models are used; the same natural object or phenomenon can be investigated using different models; the laws of physics and physical theories have their own definite limits of applicability;
2.5.3. measure physical quantities, present the results of measurements, taking into account their errors;
2.6. apply the acquired knowledge to solve physical problems.
3. Use the acquired knowledge and skills in practical activities and everyday life:
3.1. to ensure life safety in the process of using vehicles, household electrical appliances, radio and telecommunications communications; assessment of the impact on the human body and other organisms of environmental pollution; rational nature management and environmental protection;
3.2. determining one's own position in relation to environmental problems and behavior in the natural environment.
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