Law of conservation of momentum for jet motion definitions. Subject
Body impulse is a quantity equal to the product of a body's mass and its speed.
The impulse is indicated by a letter and has the same direction as the speed.
Pulse unit:
The momentum of the body is calculated by the formula: , where
The change in the momentum of the body is equal to the impulse of the force acting on it:
For a closed system of bodies it is true law of conservation of momentum:
in a closed system, the vector sum of the momenta of bodies before interaction is equal to the vector sum of momenta of bodies after interaction.
The law of conservation of momentum underlies jet propulsion.
Jet propulsion- this is the movement of the body that occurs after the separation of its part from the body.
To calculate the speed of a rocket, write down the law of conservation of momentum
and get the formula for rocket speed: =, where M is the mass of the rocket,
10. Rutherford's experiments on the scattering of α-particles. Nuclear model of the atom. Bohr's quantum postulates.
The first model of the atom was proposed by the English physicist Thomson. According to Thomson, an atom is a positively charged ball containing negatively charged electrons.
Thomson's model of the atom was incorrect, which was confirmed by the experiments of the English physicist Rutherford in 1906.
In these experiments, a narrow beam of α particles emitted by a radioactive substance was directed at thin gold foil. A screen was placed behind the foil, capable of glowing under the impacts of fast particles.
It was found that most α-particles deviate from straight-line propagation after passing through the foil, i.e. dissipate. And some alpha particles are generally thrown back.
Rutherford explained the scattering of α-particles by the fact that the positive charge is not distributed evenly over the ball, as Thomson assumed, but is concentrated in the central part of the atom - atomic nucleus. When passing near the nucleus, an alpha particle having a positive charge is repelled from it, and when it hits the nucleus, it is thrown back.
Rutherford suggested that the atom was structured like a planetary system.
But Rutherford could not explain stability (why electrons do not emit waves and fall towards a positively charged nucleus).
New ideas about the special properties of the atom were formulated by the Danish physicist Bohr in two postulates.
1st postulate. An atomic system can only be in special stationary or quantum states, each of which has a corresponding energy; In a stationary state, the atom does not radiate.
2nd postulate. When an atom transitions from one stationary state to another, a quantum of electromagnetic radiation is emitted or absorbed.
The energy of the emitted photon is equal to the difference in the energies of the atom in two states:
Planck's constant.
Lesson No. 14
Subject. Body impulse. Law of conservation of momentum. Jet propulsion.
Target: to form students’ knowledge about physical quantities - body impulse and force impulse, and the connection between them; help to understand the law of conservation of momentum; develop knowledge about jet propulsion.
Lesson type: lesson in learning new knowledge.
Equipment: a steel ball, a magnet, a glass of water, a sheet of paper, identical balls (2 or 4) on strings, a balloon, a pallet, a children's car, a glass of water and a tap.
^
Lesson plan
| Lesson steps | Time, min | Methods and forms of working with the class |
| I. Organizational stage | 2 | |
| II. Updating of reference knowledge | 5 | Frontal survey |
| III. Communicating the topic, purpose and objectives of the lesson | 2 | Determining the purpose of the lesson according to the topic study plan |
| IV. Motivation for learning activities | 2 | Reasoned explanation |
| V. Perception and initial comprehension of new material | 20 | Teacher's explanation with elements of heuristic conversation |
| VI. Consolidating new material | 10 | Self-test |
| VII. Summing up the lesson and reporting homework | 4 | Teacher's explanation, instruction |
^ Lesson progress
Organizational stage
Updating and correcting basic knowledge
Questions for the class
State Newton's first law of dynamics.
State Newton's second law of dynamics.
Formulate Newton's third law of dynamics.
Which system of bodies is called isolated or closed?
Communicating the topic, purpose and objectives of the lesson
Topic study plan
Impulse of force.
Body impulse.
Isolated phone system Law of conservation of momentum.
Jet propulsion. The movement of a rocket is like jet propulsion.
Motivation for learning activities
Like Newton's laws, conservation laws are the result of a theoretical generalization of research facts. These are the fundamental laws of physics, which are extremely important because they apply not only in mechanics,ButAnd Vother branches of physics.
Perception and initial comprehension of new material
Under the term "impulse" (from the Latin "impulsus " - push) in mechanics understand the impulse of force and the impulse of a body.
Question for the class. Do you think the result of interaction depends on time or is it determined only by the strength of interaction?
Demonstration 1. Place a steel ball on a horizontal surface and quickly pass a magnet over it. The ball will barely budge (Fig. 1,A). Repeat the experiment, passing the magnet slowly. The ball will move behind the magnet (Fig. 1, b).
Demonstration 2. Place a sheet of paper on the edge of the table and place a glass of water on it. If the sheet is pulled slowly, the glass moves with it (Fig. 2,A), and if you pull the leaf, it will be pulled out from under the glass, but the glass will remain in place (Fig. 2, b).
^ Question for the class. What do these experiments indicate?
The interaction of bodies depends not only on the force, but also on the time of its action, therefore, to characterize the action of the force, a special characteristic was introduced - the impulse of the force.
^ Force impulse
- a physical quantity that is a measure of the action of a force over a certain time interval and numerically
equal to the product of force and time eeactions: 
.
The SI unit is the newton second (N∙ s). Force impulse is a vector quantity: the direction of the force impulse coincides with the direction of the force acting on the body.
^2. Body impulse
Let's imagine that a ball weighing 40 g is thrown at a speed of 5 m/s. Such a ball can be stopped by substituting a sheet of thick cardboard or thick fabric. But if the ball is shot from a rifle at a speed of 800 m/s, then even with the help ofex thick boards it is almost impossible to stop it.
^ Question for the class. What conclusion can be drawn from this example?
To characterize movement, it is not enough to know only body mass and speed. Therefore, body impulse (or momentum) was introduced as one of the measures of mechanical motion.
^ Body impulse
- a physical quantity that is a measure of mechanical movement and is numerically determined by the product of the mass of a body and the speed of its movement: 
.
The SI unit is kilogram meter per second (kg∙m/s) . The momentum of a body is a vector quantity, its direction coincides with the direction of the speed of movement of the body.
If the body has massmmoves with speed v, and then over time interacts with another body with force F , then during this interaction the body will move with acceleration a:
, 
.
The last formula demonstrates the connection between the impulse of force and the change in the momentum of the body.
Thus, the change in the momentum of the body is equal to the impulse of the interaction force.
^ 3. Isolated phone system. Law of conservation of momentum
Isolated (orclosed) system of bodies - this is a system of bodies that interact only with each other and do not interact with bodies that are not part of this system.
Isolated systems of bodies in the full sense of the word do not exist; this is an idealization. All bodies in the world interact. But in a number of cases, real systems can be considered as isolated, excluding from consideration those interactions that in this case are unimportant.
Demonstration 3. Elastic impact of two balls of equal mass suspended on threads (Fig. 3).
Thus, when studying the elastic impact of two identical balls, the system of balls can be considered as isolated, since at the moment of impact the gravity forces of the balls are balanced by the reaction forces of the threads, the resistance forces of the air of the balls are small and can be neglected.
Give examples of other systems that can be considered isolated.
If we again turn to the system of balls with massesT
1
AndT
2
,
which at the initial moment of time in the chosen inertial reference frame have velocities 
And
, then after a moment of time
t
you can see that their speeds as a result of interaction have changed to 
And
.
According to Newton's second law:
Because according to Newton's third law
From the resulting expression it is clear that the vector sum of the momenta of the bodies included in the closed system remains constant. This is the law of conservation of momentum.
^ 4. Jet propulsion. Rocket motion like jet propulsion
The law of conservation of momentum explains reactive motion.
^ Jet propulsion - this is the movement of a body resulting from the separation of a part from it or the release of a substance by it at a certain speed relative to the body.
Demo 4 . Inflate the balloon and then release it. The ball will move due to the gases that “flow” from it.
Demonstration 5. Place a children's car in the tray and place a glass of water on it with a tap. If you open the tap, water will start flowing out of the glass and the machine will start moving.
^ Class assignment. Give examples of jet propulsion. (Jet propulsion is carried out by airplanes flying at speeds of several thousand kilometers per hour, projectiles from the well-known Katyusha rockets, and space rockets. Jet propulsion is inherent, for example, in squids, cuttlefish, and octopuses.)
Let's look at Fig. 4. Any rocket consists of a tubular body 1, closed at one end. There is a nozzle at the second end 2. Every rocket has fuel 3. When a rocket is stationary, its total momentum is zero: the fuel and body are motionless. We will assume that the rocket fuel burns instantly. RaWithhot gases 4 under great pressure they burst out.
In this case, the rocket body moves in the direction opposite to the movement of hot gases.
Let mG υ G - projection of the gas impulse onto the axisOU, A m Toυ To- projection of the momentum of the rocket body. According to the law of conservation of momentum, the sum of the impulses of the rocket body and the escaping gases is equal to the total impulse of the rocket at launch, which, as is known, is zero. Accordingly 0 = m r υ r + m To υ To
m To υ To = - m Gυ G
It follows that the rocket body receives an impulse of the same magnitude as the gases emitted from the nozzle. Hence,
Here the “-” sign indicates that the direction of the speed of the rocket body is opposite to the direction of the speed of the outgoing gases. Therefore, in order to move a rocket in a given direction, the stream of gases emitted by the rocket must be directed opposite to the given direction of movement. As we can see, the rocket moves without interacting with other bodies, and therefore can move in space.
^ Class assignment. After analyzing the last formula, answer the question: how can you increase the speed of a rocket?
The speed of a rocket can be increased in two ways:
increase the speed of gases flowing from the rocket nozzle;
increase the mass of burned fuel.
VI. Consolidating new material
^ Self-test
Mark the correct answer in your opinion.
The impulse of the body is called:
B product of a body's mass and its speed
IN product of the force acting on the body and the speed of the body
G product of the force acting on the body and the time of its action
Specify the unit of momentum of the body.
Specify the unit of force impulse.
The change in momentum of the body is equal to:
B difference between the initial and final speed of a body
IN impulse of force
G change in body weight per unit time
Jet motion occurs:
B movement of various parts of the body relative to the center of mass of the body
^B dividing the body into parts
G separation from a body of part of its mass with a certain speed of movement relative to the rest
Determine in which reference systems the law of conservation of momentum is satisfied.
B Non-inertial D Any
Select an example that demonstrates jet propulsion.
B Pendulum swing
IN Flight of the Moth
G Falling leaves from trees
The rocket rises uniformly vertically upward. Determine how and whythe rocket's momentum changes.
B Does not change because mass decreases and speed movement increases
IN Increasing as the rocket rises higher above the ground
G Does not change because the speed is constant
Specifycorrect recording of the law of conservation of momentum.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |
| B | IN | G | IN | G | IN | A | A | A |
VII. Summing up the lesson and reporting homework
The teacher sums up the lesson and evaluates the students' activities.
Homework
Learn theoretical material from a textbook.
Characterize reactive motion as a physical phenomenon according to a generalized planacting of a physical phenomenon.
Think through a demonstration of jet propulsion, describe and explain it.
When bodies interact, the impulse of one body can be partially or completely transferred to another body. If a system of bodies is not acted upon by external forces from other bodies, then such a system is called closed.
In a closed system, the vector sum of the impulses of all bodies included in the system remains constant for any interactions of the bodies of this system with each other.
This fundamental law of nature is called law of conservation of momentum . It is a consequence of Newton's second and third laws.
Let us consider any two interacting bodies that are part of a closed system. We denote the interaction forces between these bodies by and According to Newton’s third law
If these bodies interact over time t, then the impulses of the interaction forces are equal in magnitude and directed in opposite directions:
Let us apply Newton's second law to these bodies:
Where and are the impulses of the bodies at the initial moment of time, and are the impulses of the bodies at the end of the interaction. From these relations it follows that as a result of the interaction of two bodies, their total momentum has not changed:
Law of conservation of momentum:
Considering now all possible pair interactions of bodies included in a closed system, we can conclude that the internal forces of a closed system cannot change its total momentum, that is, the vector sum of the momentum of all bodies included in this system.
Rice. 1.17.1 illustrates the law of conservation of momentum using the example off-central impact two balls of different masses, one of which was at rest before the collision.
Shown in Fig. 1.17.1 the momentum vectors of the balls before and after the collision can be projected onto the coordinate axes OX And OY. The law of conservation of momentum is also true for projections of vectors onto each axis. In particular, from the momentum diagram (Fig. 1.17.1) it follows that the projections of the vectors and momentum of both balls after the collision onto the axis OY must be identical in magnitude and have different signs so that their sum equals zero.
Law of conservation of momentum in many cases it allows one to find the velocities of interacting bodies even when the values of the acting forces are unknown. An example would be jet propulsion .
When firing a gun, a recoil– the projectile moves forward, and the gun rolls back. The projectile and the gun are two interacting bodies. The speed that a gun acquires during recoil depends only on the speed of the projectile and the mass ratio (Fig. 1.17.2). If the velocities of the gun and the projectile are denoted by and and their masses by M And m, then, based on the law of conservation of momentum, we can write in projections onto the axis OX
Based on the principle of giving jet propulsion. IN rocket When fuel burns, gases heated to a high temperature are ejected from the nozzle at high speed relative to the rocket. Let us denote the mass of emitted gases by m, and the mass of the rocket after the exhaust of gases through M. Then for the closed system “rocket + gases”, based on the law of conservation of momentum (by analogy with the problem of firing a gun), we can write:
Where V– the speed of the rocket after the exhaust of gases. In this case, it is assumed that the initial speed of the rocket was zero.
The resulting formula for the rocket speed is valid only under the condition that the entire mass of burned fuel is ejected from the rocket simultaneously. In fact, the outflow occurs gradually throughout the entire period of accelerated motion of the rocket. Each subsequent portion of gas is ejected from the rocket, which has already acquired a certain speed.
To obtain an accurate formula, the process of gas outflow from a rocket nozzle needs to be considered in more detail. Let the rocket in time t has mass M and moves at speed (Fig. 1.17.3 (1)). Over a short period of time Δ t a certain portion of gas will be ejected from the rocket with a relative speed of the rocket at the moment t + Δ t will have a speed and its mass will be equal M + Δ M, where Δ M < 0 (рис. 1.17.3 (2)). Масса выброшенных газов будет, очевидно, равна –ΔM> 0. Velocity of gases in the inertial frame OX will be equal to Apply the law of conservation of momentum. At a moment in time t + Δ t the momentum of the rocket is equal to , and the momentum of the emitted gases is equal to 
. At a moment in time t the momentum of the entire system was equal to Assuming the “rocket + gases” system is closed, we can write:
The value can be neglected, since |Δ M| << M. Dividing both sides of the last relation by Δ t and passing to the limit at Δ t→0, we get:
|
Figure 1.17.3. A rocket moving in free space (without gravity). 1 – at the moment of time t. Rocket mass M, its speed 2 – Rocket at a moment in time t + Δ t. Rocket mass M + Δ M, where Δ M < 0, ее скорость масса выброшенных газов –ΔM> 0, relative gas velocity, gas velocity in the inertial frame |
Magnitude 
is the fuel consumption per unit time. The quantity is called thrust force The reactive thrust force acts on the rocket from the side of the escaping gases; it is directed in the direction opposite to the relative speed. Ratio 
expresses Newton's second law for a body of variable mass. If gases are ejected from the rocket nozzle strictly backward (Fig. 1.17.3), then in scalar form this relationship takes the form:
Where u– relative velocity module. Using the mathematical operation of integration, from this relation we can obtain formulaTsiolkovskyfor the final speed υ of the rocket:
where is the ratio of the initial and final masses of the rocket.
It follows from it that the final speed of the rocket can exceed the relative speed of the outflow of gases. Consequently, the rocket can be accelerated to the high speeds required for space flights. But this can only be achieved by consuming a significant mass of fuel, constituting a large proportion of the initial mass of the rocket. For example, to achieve the first escape velocity υ = υ 1 = 7.9·10 3 m/s at u= 3·10 3 m/s (gas flow velocities during fuel combustion are on the order of 2–4 km/s) starting mass single stage rocket should be approximately 14 times the final mass. To achieve final speed υ = 4 u the ratio should be 50.
A significant reduction in rocket launch mass can be achieved by using multistage rockets, when the rocket stages separate as the fuel burns out. The masses of containers that contained fuel, spent engines, control systems, etc. are excluded from the process of subsequent rocket acceleration. It is along the path of creating economical multi-stage rockets that modern rocket science is developing.
space research. Semiconductor diode, pn junction and its properties. Application of semiconductor devices. Problem on applying the 1st law of thermodynamics.
Body impulse– this is the product of the body’s mass and its speed p = mv (kg * m/s) The momentum of the body is the amount of motion. The change in the momentum of the body is equal to the change in the impulse of the force. ∆p = F∆t
The sum of the momenta of bodies before interaction is equal to the sum of impulses after interaction OR: The geometric sum of the momenta of bodies in a closed system remains constant. m1v1 + m2v2 = const
The law of conservation of momentum underlies jet motion - this is a movement in which part of the body is separated, and the other receives additional acceleration.
Jet propulsion in technology: FOR EXAMPLE (in airplanes and rockets)
Jet propulsion in nature: FOR EXAMPLE (molluscs, octopuses). Space information is of great importance for the further development of science and technology. Space research will apparently lead in the near future to revolutionary changes in many areas of engineering and technology, as well as in medicine. The results of developments in the field of space technology will find application in industrial and agricultural work, in exploring the depths of the World Ocean and in polar research, in sports competitions, in the manufacture of geological equipment and in other areas. A semiconductor diode is a semiconductor device with one electrical junction and two leads (electrodes). An electron-hole junction is a region of a semiconductor in which a spatial change in the type of conductivity takes place (from the electronic n-region to the hole p-region). Semiconductor devices are used: in the motor transport complex. electronic ignition. electronic control unit. LEDs: sensors, headlights, traffic lights, etc. global positioning system. Cell Phones
6 The law of universal gravitation. Gravity. Free fall of bodies. Body weight. Weightlessness. A magnetic field. Magnetic induction, magnetic induction lines. Ampere force and its application. The task is to apply formulas for work or power of direct current.
Law of Gravity Newton's law that describes gravitational interaction within the framework of classical mechanics. This law was discovered by Newton around 1666. It states that the force of gravitational attraction between two material points of mass and separated by a distance is proportional to both masses and inversely proportional to the square of the distance between them. Gravity- a force acting on any material body located near the surface of the Earth or another astronomical body. Free fall- uniformly variable motion under the influence of gravity, when other forces acting on the body are absent or negligibly small. Weight- the force of the body on the support (or suspension or other type of fastening), preventing a fall, arising in the field of gravity P=mg. Weightlessness- a state in which the force of interaction of a body with a support (body weight), arising in connection with gravitational attraction, the action of other mass forces, in particular the inertial force that arises during the accelerated movement of a body, is absent. A magnetic field- a force field acting on moving electric charges and on bodies with a magnetic moment, regardless of the state of their motion. Magnetic induction- a vector quantity that is a force characteristic of the magnetic field (its action on charged particles) at a given point in space. Determines the force with which a magnetic field acts on a charge moving at speed.
Magnetic induction lines- lines, the tangents to which are directed in the same way as the magnetic induction vector at a given point in the field.
7 The phenomenon of electromagnetic induction, the use of this phenomenon. Law of electromagnetic induction. Lenz's rule. Job. Fur. energy. Kinetic and potential energy. Law of conservation of fur. energy. E.Z: Measuring the total resistance of an electrical circuit in a series connection. Electromagnetic induction is the phenomenon of the appearance of an electric torus in a closed circuit when the magnetic flux passing through it changes. It was discovered by Michael Faradel. The phenomenon of electric Poppy. induction used in electrical and radio engineering devices: generators, transformers, chokes, etc. Faraday's law of electromagnetic induction is the basic law of electrodynamics concerning the principles of operation of transformers, chokes, many types of electric motors and generators. The law says: for any closed loop, the induced electromotive force (EMF) is equal to the rate of change of the magnetic flux passing through this loop, taken with a minus sign. Lenz's rule determines the direction of the induction current and states: the induction current always has such a direction that it weakens the effect of the cause that excites the current. Fur. Job- is a physical quantity that is a scalar quantitative measure of the action of a force or forces on a body or system, depending on the numerical value, direction of the force (forces) and on the movement of a point (points), body or system In physics fur. energy describes the sum of potential and kinetic energies available in the components of a mechanical system. Fur. energy- this is the energy associated with the movement of an object or its position, the ability to perform mechanical work. Law of conservation of fur. energy states that if a body or system is subjected to only conservative forces (both external and internal), then the total mechanical energy of that body or system remains constant. In an isolated system, where only conservative forces act, the total mechanical energy is conserved. Potential is the potential of the body, it personifies what kind of work the body CAN do! And kinetic is the force that is already doing work. Law of energy conservation- a law of nature, established empirically and consisting in the fact that for an isolated physical system a scalar physical quantity can be introduced, which is a function of the parameters of the system and is called energy, which is conserved over time. Since the law of conservation of energy does not apply to specific quantities and phenomena, but reflects a general pattern that is applicable everywhere and always, it can be called not a law, but the principle of conservation of energy. Potential energy- energy that is determined by the relative position of interacting bodies or parts of the same body. Kinetic energy- the case when a body moves under the influence of force, it not only can, but also does some work
8 Mechanical vibrations, mechanical characteristics. vibrations: amplitude, period, frequency. Free and forced vibrations. Resonance. Self-induction. Inductance. The energy of the magnetic field of the coil. The task of applying the law of conservation of momentum Mechanical oscillation is a precisely or approximately repeating movement in which the body is displaced in one direction or the other from the equilibrium position. If a system is capable of oscillating movements, then it is called oscillatory. Properties of an oscillatory system: The system has a stable equilibrium position. When a system is removed from an equilibrium position, an internal restoring force arises in it. The system is inert. Therefore, it does not stop at the equilibrium position, but passes through it. Oscillations that occur in a system under the influence of internal forces are called free. All free vibrations dampen (for example: string vibration after impact) Vibrations performed by bodies under the influence of external periodically changing forces are called forced (for example: vibration of a metal workpiece when a blacksmith works with a hammer). Resonance- a phenomenon in which the amplitude of forced oscillations has a maximum at a certain value of the frequency of the driving force. Often this value is close to the frequency of natural oscillations, in fact it may coincide, but this is not always the case and is not the cause of resonance. Self-induction- this is the phenomenon of the occurrence of induced emf in a conducting circuit when the current flowing through the circuit changes. When the current in a circuit changes, the magnetic flux through the surface bounded by this circuit also changes proportionally. A change in this magnetic flux, due to the law of electromagnetic induction, leads to the excitation of an inductive EMF (self-induction) in this circuit. Inductance- the coefficient of proportionality between the electric current flowing in any closed circuit and the magnetic flux created by this current through the surface of which this circuit is the edge. Around the current-carrying conductor there is a magnetic field that has energy.
9 Fur. waves. Wavelength, wave speed and relationships between them. Thermonuclear reaction. Application of atomic energy. Prospects and problems of nuclear energy development. E.Z: determination of the refractive index of a glass plate. Fur. waves are disturbances propagating in an elastic medium (deviations of particles of the medium from the equilibrium position). If particle oscillations and wave propagation occur in one direction, the wave is called longitudinal, and if these movements occur in perpendicular directions, it is called transverse. Longitudinal waves, accompanied by tensile and compressive deformations, can propagate in any elastic media: gases, liquids and solids. Transverse waves propagate in those media where elastic forces appear during shear deformation, i.e. in solids. When a wave propagates, energy is transferred without matter being transferred. The speed with which a disturbance propagates in an elastic medium is called wave speed. It is determined by the elastic properties of the medium. The distance over which a wave propagates in a time equal to the period of oscillation in it is called the wavelength (lambda). Wavelength- the distance that a wave manages to cover when moving in space at the speed of light in one period, which in turn is the reciprocal of the frequency. The higher the frequency, the shorter the wavelength. Thermonuclear reaction- a type of nuclear reaction in which light atomic nuclei combine into heavier ones due to the kinetic energy of their thermal motion. The development of an industrial society is based on an ever-increasing level of production and consumption of various types of energy. (Sharply reduces the use of natural resources
10 The emergence of the atomistic hypothesis of the structure of matter and its experimental evidence: diffusion, Brownian motion. Basic provisions of the ICT. Mass, size of molecules. Electromotive force. Ohm's law for a complete circuit. The task is to apply the fur formula. work
Diffusion- this is the phenomenon of the distribution of particles of one substance between particles of another
Brownian motion- this is the movement of particles insoluble in a liquid under the action of liquid molecules. Molecular kinetic theory is the doctrine of the structure and properties of matter based on the idea of the existence of atoms and molecules as the smallest particles of chemical substances Based on molecular kinetic theory There are three main provisions: All substances - liquid, solid and gaseous - are formed from the smallest particles - molecules, which themselves consist of atoms. .Atoms and molecules are in continuous chaotic motion. Particles interact with each other by forces that are electrical in nature. The gravitational interaction between particles is negligible. m 0 is the mass of the molecule (kg). The molecule size is very small. Electromotive force strength, that is, any strength non-electrical origin, operating in quasi-stationary circuits of direct or alternating current.
Ohm's law for a complete circuit- the current strength in the circuit is proportional to the EMF acting in the circuit and inversely proportional to the sum of the circuit resistance and the internal resistance of the source.
11 Electromagnetic waves and their properties. The principle of radio communication. Invention of radio, modern means of communication. Temperature and its measurement Absolute temperature. Temperature is a measure of the average kinetic energy of molecular movement. E.Z: Measuring the optical power of a collecting lens.
Electromotive force- scalar physical quantity characterizing the work of third parties strength, that is, any strength non-electrical origin, operating in quasi-stationary circuits of direct or alternating current. Design of general circuits for organizing radio communications. Characteristics of a radio information transmission system in which telecommunication signals are transmitted via radio waves in open space. Radio- a type of wireless information transmission in which radio waves, freely propagating in space, are used as an information carrier. On May 7, 1895, Russian physicist Alexander Stepanovich Popov (1859 - 1905/06) demonstrated the world's first radio receiver. Modern means of communication- this is a telephone, walkie-talkie, etc. Temperature- a physical quantity characterizing the thermal state of bodies. Temperature is measured in degrees.
Absolute temperature is an unconditional measure of temperature and one of the main characteristics
thermodynamics. Temperature- a measure of the average kinetic energy of molecules, energy
proportional to temperature.
12 Work in thermodynamics. Internal energy. The first and second laws of thermodynamics. Alternator. Transformer. Production and transmission of electricity, energy saving in everyday life and at work. E.Z: Measuring the acceleration of gravity at a given point on the earth.
In thermodynamics the movement of the body as a whole is not considered, we are talking about the movement of parts of a macroscopic body relative to each other. As a result, the volume of the body may change, but its speed remains equal to zero . Work in thermodynamics is defined in the same way as in mechanics, but it is not equal to
a change in the kinetic energy of a body, but a change in its internal energy. Internal energy body (denoted as E or U) - the total energy of this body minus the kinetic energy of the body as a whole and the potential energy of the body in the external field of forces. Consequently, internal energy consists of the kinetic energy of the chaotic movement of molecules, the potential energy of interaction between them and intramolecular energy. First law of thermodynamics The change ΔU of the internal energy of a non-isolated thermodynamic system is equal to the difference between the amount of heat Q transferred to the system and the work A performed by the system on external bodies.
Second law of thermodynamics. It is impossible to transfer heat from a colder system to a hotter one in the absence of other simultaneous changes in both systems or surrounding bodies. an alternator is a device that produces alternating current
A transformer is a device used to lower or increase current or voltage. Energy saving - the creation of new technologies that consume less energy (new lamps, etc.)
Heat engines. Efficiency of heat engines. Heat engines and ecology. Radar, application of radar. Experimental task: measuring the wavelength of light using a diffraction grating.
Heat engine- a device that performs work by using internal energy, a heat engine that converts heat into mechanical energy, uses the dependence of the thermal expansion of a substance on temperature.
Coefficient of performance (efficiency) of a heat engine is the ratio of the work A´ performed by the engine to the amount of heat received from the heater:
The continuous development of energy, automobile and other types of transport, the increase in the consumption of coal, oil and gas in industry and for domestic needs increases the possibilities of meeting human vital needs. However, at present, the amount of chemical fuel burned annually in various heat engines is so large that protecting nature from the harmful effects of combustion products is becoming an increasingly difficult problem. The negative impact of heat engines on the environment is associated with the action of various factors.
Radar- a field of science and technology that combines methods and means of location (detection and measurement of coordinates) and determination of the properties of various objects using radio waves.
Radar-guided missiles are equipped with special autonomous devices to perform combat missions. Ocean-going ships use radar systems for navigation. On airplanes, radars are used to solve a number of problems, including determining the flight altitude relative to the ground.
THE MOMENTUM OF A BODY IS A vector quantity equal to the product of the mass of a body and its speed:
The unit of impulse in the SI system is taken to be the impulse of a body weighing 1 kg moving at a speed of 1 m/s. This unit is called KILOGRAM-METER PER SECOND (kg . m/s).
A SYSTEM OF BODIES THAT DO NOT INTERACT WITH OTHER BODIES NOT PART OF THIS SYSTEM IS CALLED CLOSED.
In a closed system of bodies, the conservation law is satisfied for momentum.
IN A CLOSED SYSTEM OF BODIES, THE GEOMETRICAL SUM OF BODY MOMENTA REMAINS CONSTANT FOR ANY INTERACTIONS OF THE BODIES OF THIS SYSTEM BETWEEN THEM.
Reactive motion is based on the law of conservation of momentum. When fuel burns, gases heated to a high temperature are ejected from the rocket nozzle at a certain speed. At the same time, they interact with the rocket. If, before the engine starts operating, the sum of pulses
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where M is the mass of the rocket; V - rocket speed;
m is the mass of emitted gases; v - gas flow rate.
From here we get the expression for the rocket speed:
The main feature of a jet engine is that in order to move, it does not need a medium with which it can interact. Therefore, a rocket is the only vehicle capable of moving in airless space.
The great Russian scientist and inventor Konstantin Eduardovich Tsiolkovsky proved the possibility of using rockets for space exploration. He developed a design diagram for the rocket and found the necessary fuel components. Tsiolkovsky's works served as the basis for the creation of the first spaceships.
The world's first artificial Earth satellite was launched in our country on October 4, 1957, and on April 12, 1961, Yuri Alekseevich Gagarin became the Earth's first cosmonaut. Currently, spacecraft are exploring other planets of the solar system, comets, and asteroids. American astronauts landed on the Moon, and a manned flight to Mars is being prepared. Scientific expeditions have been operating in orbit for a long time. Reusable spacecraft "Shuttle" and "Challenger" (USA), "Buran" (Russia) have been developed, work is underway to create a scientific station "Alpha" in Earth orbit, where scientists from different countries will work together.
Jet propulsion is also used by some living organisms. For example, squids and octopuses move by throwing out a stream of water in the direction opposite to their movement.
4/2. Experimental task on the topic “Molecular Physics”: observing changes in air pressure with changes in temperature and volume.
Connect the corrugated cylinder to a pressure gauge and measure the pressure inside the cylinder.
Place the cylinder in a vessel with hot water. What's happening?
Compress the cylinder. What's happening?
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