With a constant ideal gas concentration. Venda private school - virtual school

Ideal gas MKT type A p. 9 from 9

ICT IDEAL GAS

BASIC EQUATION MKT , ABSOLUTE TEMPERATURE

With a constant concentration of particles, the absolute temperature of the ideal gas was increased by a factor of 4. At the same time, the gas pressure

increased by 4 times

increased by 2 times

decreased by 4 times

hasn't changed

At a constant absolute temperature, the concentration of ideal gas molecules was increased by a factor of 4. In this case, the gas pressure

increased by 4 times

increased by 2 times

decreased by 4 times

hasn't changed

The vessel contains a mixture of gases - oxygen and nitrogen - with an equal concentration of molecules. Compare the pressure produced by oxygen ( R To) and nitrogen ( R but) onto the walls of the vessel.

1) the ratio R To and R but will be different at different temperatures of the gas mixture

2) R To = R but

3) R To > R but

4) R To R but

With a constant concentration of particles of an ideal gas, the average kinetic energy of the thermal motion of its molecules decreased by 4 times. In this case, the gas pressure

decreased 16 times

decreased by 2 times

decreased by 4 times

hasn't changed

As a result of cooling a monatomic ideal gas, its pressure decreased by 4 times, and the concentration of gas molecules did not change. In this case, the average kinetic energy of the thermal motion of gas molecules is

decreased 16 times

decreased by 2 times

decreased by 4 times

hasn't changed

At constant pressure, the concentration of gas molecules increased 5 times, and its mass did not change. Average kinetic energy of translational motion of gas molecules

The absolute body temperature is 300 K. On the Celsius scale, it is equal to

1) - 27 ° С 2) 27 ° C 3) 300 ° C 4) 573 ° C

The temperature of the solid dropped by 17 ° C. On the absolute scale of temperatures, this change was

1) 290 K 2) 256 K 3) 17 C 4) 0 K

Measuring pressure p, temperature T and the concentration of molecules n gas for which the conditions of ideality are satisfied, it is possible to determine

gravitational constant G

Boltzmann constantk

Planck's constant h

Rydberg constant R

According to calculations, the temperature of the liquid should be equal to 143 K. Meanwhile, the thermometer in the vessel shows a temperature of –130 ° C. It means that

the thermometer is not designed for low temperatures and requires replacement

the thermometer shows a higher temperature

the thermometer shows a lower temperature

the thermometer shows the calculated temperature

At a temperature of 0 ° C, the ice of the ice rink melts. Puddles form on the ice, and the air above it is saturated with water vapor. In which of the media (ice, puddles or water vapor) is the average energy of movement of water molecules the greatest?

1) in ice 2) in puddles 3) in water vapor 4) the same everywhere

When an ideal gas was heated, its absolute temperature doubled. How has the average kinetic energy of the thermal motion of gas molecules changed?

increased 16 times

increased by 4 times

increased by 2 times

hasn't changed

Metal cylinders with gas cannot be stored at temperatures above a certain temperature, because otherwise, they may explode. This is due to the fact that

internal gas energy depends on temperature

gas pressure depends on temperature

gas volume depends on temperature

molecules break up into atoms and energy is released

As the gas temperature in the sealed vessel decreases, the gas pressure decreases. This decrease in pressure is explained by the fact that

the energy of thermal motion of gas molecules decreases

the energy of interaction of gas molecules with each other decreases

the randomness of the movement of gas molecules decreases

the size of gas molecules decreases when it cools

In a closed vessel, the absolute temperature of the ideal gas decreased by 3 times. In this case, the gas pressure on the walls of the vessel

The concentration of molecules of a monatomic ideal gas was reduced by 5 times. At the same time, the average energy of the chaotic motion of gas molecules was doubled. As a result, the gas pressure in the vessel

decreased by 5 times

doubled

decreased by 5/2 times

decreased by 5/4 times

As a result of gas heating, the average kinetic energy of the thermal motion of its molecules increased by 4 times. How did the absolute gas temperature change?

increased by 4 times

increased by 2 times

decreased by 4 times

hasn't changed

KLIPERON-MENDELEEV EQUATION, GAS LAWS

The tank contains 20 kg of nitrogen at a temperature of 300 K and a pressure of 10 5 Pa. What is the volume of the tank?

1) 17.8 m 3 2) 1.8 · 10 -2 m 3 3) 35.6 m 3 4) 3.6 · 10 -2 m 3

A cylinder with a volume of 1.66 m 3 contains 2 kg of nitrogen at a pressure of 10 5 Pa. What is the temperature of this gas?

1) 280 ° C 2) 140 ° C 3) 7 ° C 4) - 3 ° С

At a temperature of 10 0 C and a pressure of 10 5 Pa, the density of the gas is 2.5 kg / m 3. What is the molar mass of the gas?

59 g / mol 2) 69 g / mol 3) 598 kg / mol 4) 5.8 · 10 -3 kg / mol

In a vessel of constant volume, there is an ideal gas in the amount of 2 mol. How should the absolute temperature of the vessel with gas be changed when one more mole of gas is added to the vessel so that the gas pressure on the vessel walls increases 3 times?

reduce by 3 times

reduce by 2 times

increase 2 times

increase by 3 times

In a vessel of constant volume, there is an ideal gas in the amount of 2 mol. How should the absolute temperature of the vessel with gas be changed when 1 mol of gas is released from the vessel so that the gas pressure on the vessel walls doubles?

increase 2 times

increase by 4 times

reduce by 2 times

reduce by 4 times

In a vessel of constant volume, there is an ideal gas in the amount of 1 mol. How should the absolute temperature of the vessel with gas be changed so that when another mole of gas is added to the vessel, the gas pressure on the vessel walls decreases by 2 times?

increase 2 times

reduce by 2 times

Final test in physics

Grade 11

1. The time dependence of the coordinate for some body is described by the equation x = 8t -t 2... At what point in time is the speed of the body equal to zero?

1) 8 s 2) 4 s3) 3 s4) 0 s

2. With a constant concentration of particles of an ideal gas, the average kinetic energy of the thermal motion of its molecules decreased by 4 times. In this case, the gas pressure

1) decreased 16 times

2) decreased by 2 times

3) decreased by 4 times

4) has not changed

3. With a constant mass of an ideal gas, its pressure decreased by 2 times, and the temperature increased by 2 times. How did the volume of gas change?

1) increased by 2 times

2) decreased by 2 times

3) increased by 4 times

4) has not changed

4. At a constant temperature, the volume of a given mass of an ideal gas increased 9 times. The pressure at the same time

1) increased by 3 times

2) increased 9 times

3) decreased by 3 times

4) decreased by 9 times

5. The gas in the vessel was compressed, performing work of 30 J. The internal energy of the gas increased by 25 J. Consequently, the gas

1) received from the outside an amount of heat equal to 5 J

2) gave the environment an amount of heat equal to 5 J

3) received from the outside an amount of heat equal to 55 J

4) gave the environment an amount of heat equal to 55 J

6. The distance between two point electric charges was increased 3 times, and one of the charges was reduced 3 times. The strength of the electrical interaction between them

1) has not changed

2) decreased by 3 times

3) increased by 3 times

4) decreased by 27 times

7. Current fluctuations in the alternating current circuit are described by the equation I = 4.cos 400πt... What is the period of current fluctuations?

1) 4 c

2) 200 c

3) 0,002 c

4) 0, 005 c

8. The metal plate is illuminated with light with an energy of 6.2 eV. The work function for the metal of the plate is 2.5 eV. What is the maximum kinetic energy of the resulting photoelectrons?

1) 3.7 eV

2) 2.5 eV

3) 6.2 eV

4) 8.7 eV

9. What is the photon energy corresponding to the light wavelength λ = 6 μm?

1) 3.3. 10 -40 J

2) 4.0. 10 -39 J

3) 3.3. 10 -20 J

4) 4.0. 10 -19 J

10. An electron and a proton move at the same speed. Which of these particles has a longer de Broglie wavelength?

1) the electron

2) the proton

3) the wavelengths of these particles are the same

4) particles cannot be characterized by wavelength

IN 1.The body was thrown at an angle of 60 0 to the horizon at a speed of 100 m / s. What is the maximum height of the body? Write down the answer in meters, with an accuracy of tenths.

C1. An ideal gas first expanded at a constant temperature, then it was cooled at a constant pressure, and then heated at a constant volume, returning the gas to its original state. Plot these processes on the p-V axes. The gas mass did not change.

Solutions

This equation of uniformly accelerated motion x = x 0 + v 0x t + a x t 2/2. The equation for the speed at uniformly accelerated motion: v x = v 0x + a x t. From the equation given to us: v 0x = 8 m / s, a x = -2 m / s 2. We supply: 0 = 8-2t. Whence t = 4s.

One of the types of the basic equation of MKT gases p = 2/3. nE k. From this equation we see that if the concentration n does not change, and the average kinetic energy of molecules decreases by 4 times, then the pressure will decrease by 4 times.

According to the Mendeleev-Clapeyron equation pV = (m / M). RT, if the pressure decreased by 2 times, and the temperature increased by 2 times, then the volume increased by 4 times.

Because the temperature and mass of the gas do not change, this is an isothermal process. For it, the Boyle-Mariotte law pV = const is satisfied. From this law we see that if the volume increased 9 times, then the pressure decreased 9 times.

The first law of thermodynamics: ΔU = A + Q. By condition A = 30J, ΔU = 25J. Then, Q = -5J, i.e. the body gave the environment 5 J of the amount of heat.

Coulomb's law: F e = k | q 1 | ... | q 2 | / r 2. From this law we see that if one of the charges is reduced by 3 times, and the distance between the charges is increased by 3 times, then the electric force will decrease by 27 times.

General view of the harmonic dependence of current fluctuations: I = I m cos (ωt + φ). From the comparison we see that the cyclic frequency is ω = 400π. Because ω = 2πν, then the oscillation frequency ν = 200Hz. Because period T = 1 / ν, then T = 0.005s.

Einstein's equation for the photoelectric effect: h ν = A out + E k. By the condition h ν = 6.2 eV, A out = 2.5 eV. Then, E k = 3.7 eV.

Photon energy E = h ν, ν = с / λ. Substituting, we get E = 3.3. 10 -20 J.

De Broglie's formula: p = h / λ. Because p = mv, then mv = h / λ and λ = h / mv. Because the mass of the electron is less, its wavelength is longer.

IN 1. Take the throwing point as the reference body, direct the Y coordinate axis vertically upward. Then, the maximum height is equal to the projection of the displacement vector onto the Y-axis. Let's use the formula s y = (v y 2 -v 0y 2) / (2g y). At the top point, the speed is directed horizontally, therefore v y = 0. v 0y = v 0 sinα, g y = -g. Then s y = (v 0 2 sin 2 α) / (2g). Substituting, we get 369.8 m .

Control work on the topic Molecular physics for students of grade 10 with answers. The test consists of 5 options, each with 8 tasks.

Option 1

A1."The distance between neighboring particles of matter is small (they practically touch)." This statement is consistent with the model

1) only solids
2) only liquids
3) solids and liquids
4) gases, liquids and solids

A2. With a constant concentration of particles of an ideal gas, the average kinetic energy of the thermal motion of its molecules increased by 3 times. In this case, the gas pressure

1) decreased by 3 times
2) increased by 3 times
3) increased 9 times
4) has not changed

A3. What is the average kinetic energy of the chaotic translational motion of ideal gas molecules at a temperature of 27 ° C?

1) 6.2 10 -21 J
2) 4.1 · 10 -21 J
3) 2.8 10 -21 J
4) 0.6 10 -21 J

A4. Which of the graphs shown in the figure corresponds to a process carried out at a constant gas temperature?

1) A
2) B
3) B
4) G

A5. At the same temperature, saturated steam in a closed vessel differs from unsaturated steam in the same vessel.

1) pressure
2) the speed of movement of molecules

B1. The figure shows a graph of the change in the pressure of an ideal gas during its expansion.

What amount of gaseous substance (in moles) is contained in this vessel if the gas temperature is 300 K? Round your answer to the nearest whole number.

AT 2. In a vessel of constant volume, a mixture of two ideal gases, 2 mol each, was kept at room temperature. Half of the contents of the vessel was discharged and then 2 moles of the first gas were added to the vessel. How did the partial pressures of gases and their total pressure change as a result, if the temperature of the gases in the vessel was maintained constant? For each position of the first column, select the desired position of the second.

Physical quantities

B) gas pressure in the vessel

Their change

1) increased
2) decreased
3) has not changed

C1. A piston with an area of ​​10 cm 2 can move without friction in a vertical cylindrical vessel, while ensuring its tightness. A vessel with a piston, filled with gas, rests on the floor of a stationary elevator at an atmospheric pressure of 100 kPa, while the distance from the lower edge of the piston to the bottom of the vessel is 20 cm.When the elevator travels upward with an acceleration of 4 m / s 2, the piston will move by 2.5 see What is the mass of the piston if the temperature change can be ignored?

Option 2

A1."The distance between neighboring particles of matter, on average, is many times greater than the size of the particles themselves." This statement corresponds

1) only models of the structure of gases
2) only models of the structure of liquids
3) models of the structure of gases and liquids
4) models of the structure of gases, liquids and solids

A2. With a constant concentration of molecules of an ideal gas, the average kinetic energy of the thermal motion of its molecules changed by a factor of 4. How did the gas pressure change?

1) 16 times
2) 2 times
3) 4 times
4) Has not changed

A3.

1) 27 ° C
2) 45 ° C
3) 300 ° C
4) 573 ° C

A4. The figure shows graphs of four processes of changing the state of an ideal gas. Isochoric heating is a process

1) A
2) B
3) C
4) D

A5. At the same temperature, saturated steam in a closed vessel differs from unsaturated steam

1) concentration of molecules
2) the average speed of the chaotic movement of molecules
3) average energy of chaotic motion
4) absence of admixture of foreign gases

B1. The two vessels filled with 800 kPa and 600 kPa air have volumes of 3 or 5 liters, respectively. The vessels are connected by a tube, the volume of which can be neglected in comparison with the volumes of the vessels. Find the established pressure in the vessels. The temperature is constant.

AT 2.

Name

A) the amount of substance
B) the mass of the molecule
B) the number of molecules

1) m / V
2) ν N А
3) m / N А
4) m / M
5) N / V

C1. A piston with an area of ​​10 cm 2 and a mass of 5 kg can move without friction in a vertical cylindrical vessel, while ensuring its tightness. A vessel with a piston, filled with gas, rests on the floor of a stationary elevator at an atmospheric pressure of 100 kPa, while the distance from the lower edge of the piston to the bottom of the vessel is 20 cm. What will this distance be when the elevator travels downward with an acceleration of 3 m / s 2? Disregard gas temperature changes.

Option 3

A1."Particles of matter participate in continuous thermal chaotic motion." This position of the molecular-kinetic theory of the structure of matter refers to

1) gases
2) liquids
3) gases and liquids
4) gases, liquids and solids

A2. How will the pressure of an ideal monatomic gas change with an increase in the average kinetic energy of the thermal motion of its molecules by a factor of 2 and a decrease in the concentration of molecules by a factor of 2?

1) Will increase 4 times
2) Will decrease by 2 times
3) Will decrease by 4 times
4) Will not change

A3. What is the average kinetic energy of the chaotic translational motion of ideal gas molecules at a temperature of 327 ° C?

1) 1.2 · 10 -20 J
2) 6.8 10 -21 J
3) 4.1 · 10 -21 J
4) 7.5 kJ

A4. On the VT-the diagram shows graphs of changes in the state of an ideal gas. The graph line corresponds to the isobaric process

1) A
2) B
3) B
4) G

A5. In a vessel containing only steam and water, the piston is moved so that the pressure remains constant. The temperature at the same time

1) does not change
2) increases
3) decreases
4) can both decrease and increase

B1. Two vessels with a volume of 40 or 20 liters contain gas at the same temperatures but different pressures. After connecting the vessels, a pressure of 1 MPa was established in them. What was the initial pressure in the larger vessel if the initial pressure in the smaller vessel was 600 kPa? The temperature is considered constant.

AT 2. In a vessel of constant volume, a mixture of two ideal gases, 2 mol each, was kept at room temperature. Half of the contents of the vessel was discharged and then 2 moles of the second gas were added to the vessel. How did the partial pressures of gases and their total pressure change as a result, if the temperature of the gases in the vessel was maintained constant?

For each position of the first column, select the desired position of the second.

Physical quantities

A) partial pressure of the first gas
B) partial pressure of the second gas
B) gas pressure in the vessel

Their change

1) increased
2) decreased
3) has not changed

C1. A piston weighing 5 kg can move without friction in a vertical cylindrical vessel, while ensuring its tightness. A vessel with a piston, filled with gas, rests on the floor of a stationary elevator at an atmospheric pressure of 100 kPa, while the distance from the lower edge of the piston to the bottom of the vessel is 20 cm.When the elevator goes down with an acceleration of 2 m / s 2, the piston will move by 1.5 see What is the area of ​​the piston if the change in gas temperature is not taken into account?

Option 4

A1. In liquids, particles oscillate around the equilibrium position, colliding with neighboring particles. From time to time, the particle jumps to another equilibrium position. What property of liquids can be explained by this nature of particle motion?

1) Low compressibility
2) Fluidity
3) Pressure on the bottom of the vessel
4) Change in volume when heated

A2. As a result of cooling a monatomic ideal gas, its pressure decreased by 4 times, and the concentration of gas molecules did not change. In this case, the average kinetic energy of the thermal motion of gas molecules is

1) decreased 16 times
2) decreased by 2 times
3) decreased by 4 times
4) has not changed

A3. The average kinetic energy of the translational motion of gas molecules in a cylinder is 4.14 · 10 -21 J. What is the temperature of the gas in this cylinder?

1) 200 ° C
2) 200 K
3) 300 ° C
4) 300 K

A4. The figure shows a cycle carried out with an ideal gas. Isobaric heating corresponds to the area

1) AB
2) DA
3) CD
4) BC

A5. With a decrease in the volume of saturated steam at a constant temperature, its pressure

1) increases
2) decreases
3) increases for some vapors, and decreases for others
4) does not change

B1. The figure shows a graph of the dependence of the gas pressure in a sealed vessel on its temperature.

The volume of the vessel is 0.4 m 3. How many moles of gas is there in this vessel? Round your answer to the nearest whole number.

AT 2. Establish a correspondence between the name of a physical quantity and the formula by which it can be determined.

Name

A) concentration of molecules
B) the number of molecules
B) the mass of the molecule

1) m / V
2) ν N А
3) m / N А
4) m / M
5) N / V

C1. A piston with an area of ​​15 cm 2 and a mass of 6 kg can move without friction in a vertical cylindrical vessel, while ensuring its tightness. A vessel with a piston, filled with gas, rests on the floor of a stationary elevator at an atmospheric pressure of 100 kPa. In this case, the distance from the lower edge of the piston to the bottom of the vessel is 20 cm. When the lift begins to move upward with acceleration, the piston is displaced by 2 cm. With what acceleration does the lift move if the change in gas temperature can be ignored?

Option 5

A1. The least orderliness in the arrangement of particles is characteristic for

1) gases
2) liquids
3) crystalline bodies
4) amorphous bodies

A2. How will the pressure of an ideal monatomic gas change if the average kinetic energy of the thermal motion of molecules and the concentration are reduced by a factor of 2?

1) Will increase 4 times
2) Will decrease by 2 times
3) Will decrease by 4 times
4) Will not change

A3. At what temperature is the average kinetic energy of translational motion of gas molecules equal to 6.21 · 10 -21 J?

1) 27 K
2) 45 K
3) 300 K
4) 573 K

A4. The figure shows a cycle carried out with an ideal gas. Isobaric cooling corresponds to the section

1) AB
2) DA
3) CD
4) BC

A5. The vessel under the piston contains only saturated water vapor. How will the pressure in the vessel change if you start to squeeze the vapors, keeping the vessel temperature constant?

1) The pressure will constantly rise
2) The pressure will constantly drop
3) The pressure will remain constant
4) The pressure will stay constant and then start to drop

B1. On the picture. shows a graph of the isothermal expansion of hydrogen.

The mass of hydrogen is 40 g. Determine its temperature. The molar mass of hydrogen is 0.002 kg / mol. Round your answer to the nearest whole number.

AT 2. Establish a correspondence between the name of a physical quantity and the formula by which it can be determined.

Name

A) density of matter
B) the amount of substance
B) the mass of the molecule

1) N / V
2) ν N А
3) m / N А
4) m / M
5) m / V

C1. A piston with an area of ​​10 cm 2 and a mass of 5 kg can move without friction in a vertical cylindrical vessel, while ensuring its tightness. A vessel with a piston, filled with gas, rests on the floor of a stationary elevator at an atmospheric pressure of 100 kPa, while the distance from the bottom edge of the piston to the bottom of the vessel is 20 cm. What will this distance be when the elevator travels upward with an acceleration of 2 m / s 2? Disregard gas temperature changes.

Answers to the test on the topic Molecular Physics Grade 10
Option 1
A1-3
A2-2
A3-1
A4-3
A5-1
IN 1. 20 mol
AT 2. 123
C1. 5.56 kg
Option 2
A1-1
A2-3
A3-1
A4-3
A5-1
IN 1. 675 kPa
AT 2. 432
C1. 22.22 cm
Option 3
A1-4
A2-4
A3-1
A4-1
A5-1
IN 1. 1.2 MPa
AT 2. 213
C1. 9.3 cm 2
Option 4
A1-2
A2-3
A3-2
A4-1
A5-4
IN 1. 16 mol
AT 2. 523
C1. 3.89 m / s 2
Option 5
A1-1
A2-3
A3-3
A4-3
A5-3
IN 1. 301 C
AT 2. 543
C1. 18.75 cm

Unified State Exam in Physics, 2003
demo version

Part A

A1. The figures show the graphs of the dependence of the acceleration module on the time of movement. Which of the graphs corresponds to the uniform rectilinear motion?

1)		2)
3)		4)

Solution. With a uniform rectilinear motion, the acceleration is zero.

Correct answer: 2.

A2. The rocket engine of the first Soviet experimental liquid fuel rocket had a thrust force of 660 N. The rocket launch mass was 30 kg. What acceleration did the rocket acquire during launch?

1)
2)
3)
4)

Solution. Two forces act on the rocket: gravity ( mg), directed downward, and the traction force ( F) pointing up. According to Newton's second law:

Correct answer: 1.

A3. With a 3-fold increase in the distance between the centers of spherical bodies, the force of gravitational attraction

Solution. The force of gravitational attraction of two spherical bodies is

.

With an increase in 3 times the distance between their centers, the force of gravitational attraction decreases 9 times.

Correct answer: 4.

A4. The figure shows a thin weightless rod, to which forces and are applied at points 1 and 3. At what point should the axis of rotation be located so that the rod is in equilibrium?

1)	at point 2
2)	at point 6
3)	at point 4
4)	at point 5

Solution. The equilibrium condition for the rod is equality, where and are the distances from the axis of rotation to the points of application of forces. Since the second force is 3 times greater than the first, the point of its application should be located 3 times closer to the axis of rotation. This means that the axis of rotation is located either at point 2.5 or at point 4. If the axis of rotation is at point 2.5, then the forces rotate the rod in one direction and do not balance each other. When the axis of rotation is located at point 4, the forces rotate the rod in different directions, balancing each other.

Correct answer: 3.

A5. The boy threw a soccer ball weighing 0.4 kg to a height of 3 m. How much has the potential energy of the ball changed?

Solution. In general, with harmonic vibrations, the coordinate of the body changes according to the law, where A- vibration amplitude, ω - cyclic vibration frequency. The vibration amplitude is 0.9 m.

Correct answer: 3.

A7. The human ear can perceive sounds with a frequency of 20 to 20,000 Hz. What wavelength range corresponds to the interval of audibility of sound vibrations? Take the speed of sound in air equal to 340 m / s.

1)	from 20 to 20,000 m
2)	from 6800 to 6800000 m
3)	from 0.06 to 58.8 m
4)	from 0.017 to 17 m

Solution. The wavelength λ is related to the vibration frequency ν by the relationship, where v- wave propagation speed. The minimum wavelength of audible sound vibrations is

,

and the maximum wavelength of audible sound vibrations is

.

Correct answer: 4.

A8. Diffusion occurs faster with increasing temperature of the substance, because

Solution. With an increase in temperature, diffusion occurs faster due to an increase in the speed of particle movement.

Correct answer: 1.

A9. With a constant concentration of particles of an ideal gas, the average kinetic energy of the thermal motion of its molecules increased by 3 times. In this case, the gas pressure

Solution. According to the basic equation of molecular kinetic theory, the pressure of an ideal gas p associated with concentration n and the average kinetic energy of motion of its molecules by the ratio:

With a constant concentration of particles and an increase in their average kinetic energy by a factor of 3, the pressure increases by a factor of 3.

Correct answer: 2.

A10. The figure shows a graph of the dependence of the gas pressure on the vessel walls on temperature. What is the process of changing the state of the gas depicted?

Solution. The figure shows the isochoric process, which went in the direction of decreasing temperature. This means that the figure shows isochoric cooling.

Correct answer: 2.

A11. When cooling a solid with a mass m body temperature dropped by Δ T... Which of the following formulas should be used to calculate the amount of heat given off by the body Q? c- specific heat capacity of the substance.

1)
2)
3)
4)

Solution. The amount of heat given off by the body is calculated by the formula.

Correct answer: 1.

A12. Internal energy of an ideal gas when it is cooled

Solution. The internal energy of an ideal gas is equal to, where is the heat capacity of the gas at constant volume, T- its temperature. The heat capacity of an ideal gas does not depend on temperature. With decreasing temperature, the internal energy of an ideal gas decreases.

Correct answer: 2.

A13. The boiling point of water depends on

Solution. Boiling of a liquid occurs at a temperature at which the saturated vapor pressure becomes equal to the external pressure. This means that the boiling point of water depends on atmospheric pressure.

Correct answer: 3.

A14. The figure shows a graph of melting and crystallization of naphthalene. Which of the points corresponds to the beginning of the solidification of the substance?

1)	point 2
2)	point 4
3)	point 5
4)	point 6

Solution. Solidification - the transition from a liquid to a solid state when cooled. Cooling corresponds to part of the schedule 4–7. In the process of hardening, the temperature of the substance remains constant, this corresponds to part of the graph 5-6. Point 5 corresponds to the beginning of the solidification of the substance.

Correct answer: 3.

A15. How will the force of the Coulomb interaction of two stationary point charges change if the distance between them is increased by n once?

Solution. The force of the Coulomb interaction of two stationary point charges is

where k- constant value, and - charge values, R- the distance between them. If the distance between them is increased by n times, then the force will decrease in times.

Correct answer: 4.

A16. If the cross-sectional area of ​​a uniform cylindrical conductor and the electric voltage at its ends increase 2 times, then the current flowing through it,

Solution. The current flowing through the conductor is equal to, where U- tension at its ends, R- its resistance, equal to, where ρ is the specific resistance of the conductor material, l- its length, S- cross-sectional area. Thus, the current strength is. With an increase in 2 times the voltage at its ends of the conductor and its cross-sectional area, the current flowing through it increases by 4 times.

Correct answer: 3.

A17. How will the power consumed by an electric lamp change if, without changing its electrical resistance, reduce the voltage across it by 3 times?

Solution. The power consumption is where U- voltage, R-resistance. With a constant resistance and a decrease in voltage by 3 times, the power consumption is reduced by 9 times.

Correct answer: 2.

A18. What should be done in order to change the poles of the magnetic field of the current coil?

Solution. When the direction of the current in the coil changes, the poles of the magnetic field generated by it are reversed.

Correct answer: 2.

A19. Will the electrical capacity of the capacitor change if the charge on its plates is increased by n once?

Solution. The capacitance of a capacitor does not depend on the charge on its plates.

Correct answer: 3.

A20. The oscillatory circuit of the radio receiver is tuned to a radio station transmitting at a wavelength of 100 m. How should the capacitance of the capacitor of the oscillatory circuit be changed so that it is tuned to a wavelength of 25 m? The inductance of the coil is considered unchanged.

Solution. The resonant frequency of the oscillating circuit is

where C- capacitance of the capacitor, L- inductance of the coil. The contour is tuned to the wavelength

,

where c is the speed of light. To tune the radio receiver to a four times shorter wavelength, it is necessary to reduce the capacitance of the capacitor by 16 times.

Correct answer: 4.

A21. The camera lens is a collecting lens. When photographing an object, it gives an image on film

Solution. When photographing objects that are at a distance greater than the focal length of the lens, a true inverted image is obtained on the film.

Correct answer: 3.

A22. Two cars are moving in the same direction at speeds and relative to the Earth's surface. The speed of light from the headlights of the first car in the frame of reference associated with the other car is

1)
2)
3)
4)	c

Solution. According to the postulate of the special theory of relativity, the speed of light is the same in all reference frames and does not depend on the speed of the source or receiver of light.

Correct answer: 4.

A23. The figure shows variants of the graph of the dependence of the maximum energy of photoelectrons on the energy of photons incident on the photocathode. When does the graph comply with the laws of the photoelectric effect?

1)	1
2)	2
3)	3
4)	4

Solution. An experimental study of the photoelectric effect has shown that there are frequencies at which the photoeffect is not observed. Only for graph 3 there are such frequencies.

Correct answer: 3.

A24. Which of the following statements correctly describes the ability of atoms to emit and absorb energy? Isolated atoms can

Solution. Isolated atoms can emit only a certain discrete set of energy values ​​and absorb a discrete set of energy values ​​less than the ionization energy, and any portion of the energy exceeding the ionization energy.

Correct answer: none.

A25. Which of the graphs of the dependence of the number of non-decayed nuclei ( N) from time to time correctly reflects the law of radioactive decay?

Solution. According to the law of conservation of momentum, the boat speed will be equal to

Correct answer: 3.

A27. A heat engine with an efficiency of 40% receives 100 J from the heater per cycle. What amount of heat does the machine give off to the refrigerator per cycle?

1)	40 J
2)	60 J
3)	100 J
4)	160 J

Solution. The efficiency of the heat engine is equal. The amount of heat given to the refrigerator per cycle is equal.

Correct answer: 2.

A28. The magnet is removed from the ring as shown in the figure. Which pole of the magnet is closer to the ring?

Solution. The magnetic field created by the induction current is directed from right to left inside the ring. The ring can be thought of as a magnet with the north pole on the left. According to Lenz's rule, this magnet should prevent the removal of the moving magnet and, therefore, attract it. Thus, the moving magnet also has the north pole on the left.

Correct answer: 1.

A29. A lens made of two thin spherical glasses of the same radius, between which there is air (air lens), was lowered into water (see Fig.). How does this lens work?

Solution. Since the refractive index of air is less than the refractive index of water, the air lens is diffuse.

Correct answer: 2.

A30. What is the binding energy of the sodium isotope nucleus? The mass of the nucleus is 22.9898 amu. e. m Round the answer to whole numbers.

1)
2)
3)
4)	253 J

Solution. The sodium isotope nucleus consists of 11 protons and 12 neutrons. The mass defect is

The binding energy is

Correct answer: 2.

Part B

IN 1. A ball attached to a spring performs harmonic oscillations on a smooth horizontal plane with an amplitude of 10 cm. How much will the ball move from the equilibrium position during the time during which its kinetic energy is halved? Express your answer in centimeters and round to the nearest whole number?

Solution. In the equilibrium position, the system has only kinetic energy, and at maximum deviation, only potential energy. According to the law of conservation of energy, at that moment in time when the kinetic energy is halved, the potential energy will also be equal to half of the maximum:

.

From where we get:

.

AT 2. What amount of heat will be released during isobaric cooling of 80 g of helium from 200 ° C to 100 ° C? Express your answer in kilojoules (kJ) and round to the nearest whole number?

Solution. Helium is a monoatomic gas with a molar mass equal to M= 4 g / mol. 80 g of helium contains 20 mol. The specific heat of helium at constant pressure is. When cooled, it will stand out

AT 3. Resistance shorted conductor R= 3 ohm is in a magnetic field. As a result of the change in this field, the magnetic flux penetrating the contour increased from before ... What charge has passed through the cross section of the conductor? Express your answer in milliculones (mC).

Solution. When the magnetic flux changes in a closed conductor, an EMF arises, equal to. Under the action of this EMF, a current flows in the circuit, and during the time Δ t charge will pass through the cross-section of the conductor

AT 4. Performing the experimental task, the student had to determine the period of the diffraction grating. To this end, he directed a light beam onto a diffraction grating through a red filter, which transmits light with a wavelength of 0.76 microns. The diffraction grating was at a distance of 1 m from the screen. On the screen, the distance between the first-order spectra turned out to be 15.2 cm. What value of the period of the diffraction grating was obtained by the student? Express your answer in micrometers (μm). (At small angles.)

Solution. Let us denote the distance from the diffraction grating to the screen R= 1 m. The deflection angles are related to the grating constant and the wavelength of light by equality. For the first order we have:

The distance between the spectra of the first order on the screen is

.

AT 5. Determine the energy released during the following reaction:. Express your answer in picojoules (pJ) and round to the nearest whole number.

Solution. Using the tabular data on the rest energy of the nuclei of the elements participating in the reaction, we determine the released energy:

Part C

C1. A trolley weighing 0.8 kg moves by inertia at a speed of 2.5 m / s. A piece of plasticine weighing 0.2 kg vertically falls onto the cart from a height of 50 cm and sticks to it. Calculate the energy that has passed into the internal with this impact.

Solution. At the moment of impact, the speed of the plasticine is equal and directed vertically downward. This speed was completely absorbed by the reaction force of the support. All the kinetic energy of the falling piece of plasticine has passed into the internal energy:

At the moment a piece of plasticine sticks to the cart, the friction forces equalize the horizontal components of their velocities. Part of the kinetic energy of the cart has passed into the internal energy. Using the law of conservation of momentum, we determine the speed of the trolley with plasticine after the collision:

Into the internal energy passed

As a result, the energy that passed into the internal one during this impact is equal to

Answer: 1.5 J.

C2. A certain amount of helium expands: first adiabatically, and then isobaric. The final gas temperature is equal to the initial one. During adiabatic expansion, the gas performed work equal to 4.5 kJ. What is the work of the gas for the whole process?

Solution. Let's depict the processes on the diagram (see fig.). 1-2 - adiabatic expansion, 2-3 - isobaric expansion. By condition, the temperatures at points 1 and 3 are equal; the work done by the gas in process 1–2 is ... Helium is a monoatomic gas, therefore its heat capacity at constant volume is equal to, where ν is the amount of the gas substance. Using the first law of thermodynamics for process 1–2, we get:

Gas work in process 2-3 can be determined by the formula. Using the Mendeleev - Clapeyron equation and equality, we get:

The gas work for the entire process is

Answer: 7.5 kJ.

C3. A small charged ball weighing 50 g, having a charge of 1 μC, moves from a height of 0.5 m along an inclined plane with an inclination angle of 30 °. At the apex of the right angle formed by the height and the horizontal, there is a fixed charge of 7.4 μC. What is the speed of the ball at the base of the inclined plane if its initial speed is zero? Friction is neglected.

Solution. The small ball is in the gravity field of the Earth and in the electrostatic field created by the second charge. Both fields are potential, so the law of conservation of energy can be used to determine the speed of the ball. In the initial position, the ball is at a height and at a distance from the second charge. In the final position, the ball is at zero height and at a distance from the second charge. Thus:

Answer: 3.5 m / s.

C4. When a metal is irradiated with light with a wavelength of 245 nm, a photoelectric effect is observed. The work function of an electron from a metal is 2.4 eV. Calculate the amount of voltage that needs to be applied to the metal in order to reduce the maximum speed of the emitted photoelectrons by a factor of 2.

Solution. The wavelength (λ) of the incident light is related to its frequency (ν) by equality, where c is the speed of light. Using Einstein's formula for the photoelectric effect, we determine the kinetic energy of photoelectrons:

The work of the electric field is equal. The work should be such as to reduce the maximum speed of emitted photoelectrons by a factor of 2:

Answer: 2 V.

C5. A vacuum diode, in which the anode (positive electrode) and cathode (negative electrode) are parallel plates, operates in a mode when the relationship between current and voltage is fulfilled (where but- some constant). How many times will the force acting on the anode due to the impact of electrons increase if the voltage across the diode is doubled? Consider the initial velocity of the outgoing electrons to be zero.

Solution. When the voltage is doubled, the current will increase in times. The number of electrons striking the anode per unit of time will increase by the same factor. At the same time, the work of the electric field in the diode and, as a consequence, the kinetic energy of the colliding electrons will double. The speed of the particles will increase in times, the transferred momentum and the force of pressure of individual electrons will increase by the same amount. Thus, the force acting on the anode will increase by times.