Mechanical movement called a change in the position of a body relative to other bodies
Reference system called the body of reference, the coordinate system associated with it and the clock.
Body of reference name the body relative to which the position of other bodies is considered.
Material point is a body whose dimensions can be neglected in this problem.
Trajectory called a mental line that a material point describes during its movement.
According to the shape of the trajectory, the movement is divided into:
A) rectilinear- the trajectory is a straight line segment;
b) curvilinear- the trajectory is a segment of a curve.
Path is the length of the trajectory that a material point describes over a given period of time. This is a scalar quantity.
Moving is a vector connecting the initial position of a material point with its final position (see figure).
It is very important to understand how a path differs from a movement. The most important difference is that movement is a vector with a beginning at the point of departure and an end at the destination (it does not matter at all what route this movement took). And the path is, on the contrary, a scalar quantity that reflects the length of the trajectory traveled.
Uniform linear movement called a movement in which a material point makes the same movements over any equal periods of time
Speed of uniform linear motion is called the ratio of movement to the time during which this movement occurred:
For uneven motion they use the concept average speed. Average speed is often introduced as a scalar quantity. This is the speed of such uniform motion in which the body travels the same path in the same time as in uneven motion:
Instant speed call the speed of a body at a given point in the trajectory or at a given moment in time.
Uniformly accelerated linear motion- this is a rectilinear movement in which the instantaneous speed for any equal periods of time changes by the same amount
The dependence of the body coordinates on time in uniform rectilinear motion has the form: x = x 0 + V x t, where x 0 is the initial coordinate of the body, V x is the speed of movement.
Free fall called uniformly accelerated motion with constant acceleration g = 9.8 m/s 2, independent of the mass of the falling body. It occurs only under the influence of gravity.
Free fall speed is calculated using the formula:
Vertical movement is calculated using the formula:
One type of motion of a material point is motion in a circle. With such movement, the speed of the body is directed along a tangent drawn to the circle at the point where the body is located (linear speed). You can describe the position of a body on a circle using a radius drawn from the center of the circle to the body. The displacement of a body when moving in a circle is described by turning the radius of the circle connecting the center of the circle with the body. The ratio of the angle of rotation of the radius to the period of time during which this rotation occurred characterizes the speed of movement of the body in a circle and is called angular velocity ω:
Angular velocity is related to linear velocity by the relation
where r is the radius of the circle.
The time it takes a body to complete a complete revolution is called circulation period. The reciprocal of the period is the circulation frequency - ν
Since during uniform motion in a circle the velocity module does not change, but the direction of the velocity changes, with such motion there is acceleration. He is called centripetal acceleration, it is directed radially to the center of the circle:
Basic concepts and laws of dynamics
The part of mechanics that studies the reasons that caused the acceleration of bodies is called dynamics
Newton's first law:
There are reference systems relative to which a body maintains its speed constant or is at rest if other bodies do not act on it or the action of other bodies is compensated.
The property of a body to maintain a state of rest or uniform linear motion with balanced external forces acting on it is called inertia. The phenomenon of maintaining the speed of a body under balanced external forces is called inertia. Inertial reference systems are systems in which Newton's first law is satisfied.
Galileo's principle of relativity:
in all inertial reference systems under the same initial conditions, all mechanical phenomena proceed in the same way, i.e. subject to the same laws
Weight is a measure of body inertia
Force is a quantitative measure of the interaction of bodies.
Newton's second law:
The force acting on a body is equal to the product of the mass of the body and the acceleration imparted by this force:
$F↖(→) = m⋅a↖(→)$
The addition of forces consists of finding the resultant of several forces, which produces the same effect as several simultaneously acting forces.
Newton's third law:
The forces with which two bodies act on each other are located on the same straight line, equal in magnitude and opposite in direction:
$F_1↖(→) = -F_2↖(→) $
Newton's III law emphasizes that the action of bodies on each other is in the nature of interaction. If body A acts on body B, then body B acts on body A (see figure).
Or in short, the force of action is equal to the force of reaction. The question often arises: why does a horse pull a sled if these bodies interact with equal forces? This is possible only through interaction with the third body - the Earth. The force with which the hooves press into the ground must be greater than the frictional force of the sled on the ground. Otherwise, the hooves will slip and the horse will not move.
If a body is subjected to deformation, forces arise that prevent this deformation. Such forces are called elastic forces.
Hooke's law written in the form
where k is the spring stiffness, x is the deformation of the body. The “−” sign indicates that the force and deformation are directed in different directions.
When bodies move relative to each other, forces arise that impede the movement. These forces are called friction forces. A distinction is made between static friction and sliding friction. Sliding friction force calculated by the formula
where N is the support reaction force, µ is the friction coefficient.
This force does not depend on the area of the rubbing bodies. The friction coefficient depends on the material from which the bodies are made and the quality of their surface treatment.
Static friction occurs if the bodies do not move relative to each other. The static friction force can vary from zero to a certain maximum value
By gravitational forces are the forces with which any two bodies are attracted to each other.
Law of universal gravitation:any two bodies are attracted to each other with a force directly proportional to the product of their masses and inversely proportional to the square of the distance between them.
Here R is the distance between the bodies. The law of universal gravitation in this form is valid either for material points or for spherical bodies.
Body weight called the force with which the body presses on a horizontal support or stretches the suspension.
Gravity- this is the force with which all bodies are attracted to the Earth:
With a stationary support, the weight of the body is equal in magnitude to the force of gravity:
If a body moves vertically with acceleration, its weight will change.
When a body moves with upward acceleration, its weight
It can be seen that the weight of the body is greater than the weight of the body at rest.
When a body moves with downward acceleration, its weight
In this case, the weight of the body is less than the weight of the body at rest.
Weightlessness is the movement of a body in which its acceleration is equal to the acceleration of gravity, i.e. a = g. This is possible if only one force acts on the body - gravity.
Artificial Earth satellite- this is a body that has a speed V1 sufficient to move in a circle around the Earth
There is only one force acting on the Earth's satellite - the force of gravity directed towards the center of the Earth
First escape velocity- this is the speed that must be imparted to the body so that it revolves around the planet in a circular orbit.
where R is the distance from the center of the planet to the satellite.
For the Earth, near its surface, the first escape velocity is equal to
1.3. Basic concepts and laws of statics and hydrostatics
A body (material point) is in a state of equilibrium if the vector sum of the forces acting on it is equal to zero. There are 3 types of equilibrium: stable, unstable and indifferent. If, when a body is removed from an equilibrium position, forces arise that tend to bring this body back, this stable balance. If forces arise that tend to move the body further from the equilibrium position, this unstable position; if no forces arise - indifferent(see Fig. 3).
When we are not talking about a material point, but about a body that can have an axis of rotation, then in order to achieve an equilibrium position, in addition to the equality of the sum of forces acting on the body to zero, it is necessary that the algebraic sum of the moments of all forces acting on the body be equal to zero.
Here d is the force arm. Shoulder of strength d is the distance from the axis of rotation to the line of action of the force.
Lever equilibrium condition:
the algebraic sum of the moments of all forces rotating the body is equal to zero.
Pressure is a physical quantity equal to the ratio of the force acting on a platform perpendicular to this force to the area of the platform:
Valid for liquids and gases Pascal's law:
pressure spreads in all directions without changes.
If a liquid or gas is in a gravity field, then each layer above presses on the layers below, and as the liquid or gas is immersed inside, the pressure increases. For liquids
where ρ is the density of the liquid, h is the depth of penetration into the liquid.
A homogeneous liquid in communicating vessels is established at the same level. If liquid with different densities is poured into the elbows of communicating vessels, then the liquid with a higher density is installed at a lower height. In this case
The heights of liquid columns are inversely proportional to densities:
Hydraulic Press is a vessel filled with oil or other liquid, in which two holes are cut, closed by pistons. The pistons have different areas. If a certain force is applied to one piston, then the force applied to the second piston turns out to be different.
Thus, the hydraulic press serves to convert the magnitude of the force. Since the pressure under the pistons must be the same, then 
Then A1 = A2.
A body immersed in a liquid or gas is acted upon by an upward buoyant force from the side of this liquid or gas, which is called by the power of Archimedes
The magnitude of the buoyancy force is determined by Archimedes' law: a body immersed in a liquid or gas is acted upon by a buoyant force directed vertically upward and equal to the weight of the liquid or gas displaced by the body:
where ρ liquid is the density of the liquid in which the body is immersed; V submergence is the volume of the submerged part of the body.
Body floating condition- a body floats in a liquid or gas when the buoyant force acting on the body is equal to the force of gravity acting on the body.
1.4. Conservation laws
Body impulse is a physical quantity equal to the product of a body’s mass and its speed:Momentum is a vector quantity. [p] = kg m/s. Along with body impulse, they often use impulse of power. This is the product of force and the duration of its action
The change in the momentum of a body is equal to the momentum of the force acting on this body. For an isolated system of bodies (a system whose bodies interact only with each other) law of conservation of momentum: the sum of the impulses of the bodies of an isolated system before interaction is equal to the sum of the impulses of the same bodies after the interaction.
Mechanical work called a physical quantity that is equal to the product of the force acting on the body, the displacement of the body and the cosine of the angle between the direction of the force and the displacement:
Power is the work done per unit of time:
The ability of a body to do work is characterized by a quantity called energy. Mechanical energy is divided into kinetic and potential. If a body can do work due to its motion, it is said to have kinetic energy. The kinetic energy of the translational motion of a material point is calculated by the formula
If a body can do work by changing its position relative to other bodies or by changing the position of parts of the body, it has potential energy. An example of potential energy: a body raised above the ground, its energy is calculated using the formula
where h is the lift height
Compressed spring energy:
where k is the spring stiffness coefficient, x is the absolute deformation of the spring.
The sum of potential and kinetic energy is mechanical energy. For an isolated system of bodies in mechanics, law of conservation of mechanical energy: if there are no frictional forces between the bodies of an isolated system (or other forces leading to energy dissipation), then the sum of the mechanical energies of the bodies of this system does not change (the law of conservation of energy in mechanics). If there are friction forces between the bodies of an isolated system, then during interaction part of the mechanical energy of the bodies turns into internal energy.
1.5. Mechanical vibrations and waves
Oscillations movements that have varying degrees of repeatability over time are called. Oscillations are called periodic if the values of physical quantities that change during the oscillation process are repeated at regular intervals.Harmonic vibrations are called such oscillations in which the oscillating physical quantity x changes according to the law of sine or cosine, i.e.
The quantity A equal to the largest absolute value of the fluctuating physical quantity x is called amplitude of oscillations. The expression α = ωt + ϕ determines the value of x at a given time and is called the oscillation phase. Period T is the time it takes for an oscillating body to complete one complete oscillation. Frequency of periodic oscillations The number of complete oscillations completed per unit of time is called:
Frequency is measured in s -1. This unit is called hertz (Hz).
Mathematical pendulum is a material point of mass m suspended on a weightless inextensible thread and oscillating in a vertical plane.
If one end of the spring is fixed motionless, and a body of mass m is attached to its other end, then when the body is removed from the equilibrium position, the spring will stretch and oscillations of the body on the spring will occur in the horizontal or vertical plane. Such a pendulum is called a spring pendulum.
Period of oscillation of a mathematical pendulum determined by the formula 
where l is the length of the pendulum.
Period of oscillation of a load on a spring determined by the formula 
where k is the spring stiffness, m is the mass of the load.
Propagation of vibrations in elastic media.
A medium is called elastic if there are interaction forces between its particles. Waves are the process of propagation of vibrations in elastic media.
The wave is called transverse, if the particles of the medium oscillate in directions perpendicular to the direction of propagation of the wave. The wave is called longitudinal, if the vibrations of the particles of the medium occur in the direction of wave propagation.
Wavelength is the distance between two closest points oscillating in the same phase:
where v is the speed of wave propagation.
Sound waves are called waves in which oscillations occur with frequencies from 20 to 20,000 Hz.
The speed of sound varies in different environments. The speed of sound in air is 340 m/s.
Ultrasonic waves are called waves whose oscillation frequency exceeds 20,000 Hz. Ultrasonic waves are not perceived by the human ear.
>>Physics: Speed during uniformly accelerated motion
The theory of uniformly accelerated motion was developed by the famous Italian scientist Galileo Galilei. In his book “Conversations and Mathematical Proofs Concerning Two New Branches of Science Relating to Mechanics and Local Motion,” published in 1638, Galileo first defined uniformly accelerated motion and proved a number of theorems that described its laws.
Getting Started Studying uniformly accelerated linear motion, let us first find out how the speed of a body is found if the acceleration of this body and the time of movement are known.
With an initial speed equal to zero ( V 0 = 0),
V= at (3.1)
This formula shows that To find the speed of a body after time I after the start of movement, the acceleration of the body must be multiplied by the time of movement.
In the opposite case, when the body makes slow motion and eventually stops ( V= 0), the acceleration formula allows us to find the initial speed of the body:
V 0 = at (3.2)
A clear picture of how the speed of a body changes during uniformly accelerated motion can be obtained by constructing speed graph.
Speed charts were first introduced in the mid-14th century. Franciscan scientist-monk Giovanni di Casalis and the archdeacon of Rouen Cathedral Nicolas Oresme, who later became an adviser to the French king Charles V. They proposed to put time on the horizontal axis, and speed along the vertical axis. In such a coordinate system, velocity graphs for uniformly accelerated motion look like straight lines, the slope of which shows how quickly the speed changes over time.
Formula (3.1), which describes movement with increasing speed, corresponds, for example, to the speed graph shown in Figure 5. The graph shown in Figure 6 corresponds to movement with decreasing speed.
During uniformly accelerated motion, the speed of a body changes continuously. Velocity graphs allow you to determine the speed of a body at different times. But sometimes it is not necessary to know the speed at one or another specific moment in time (this speed is called instant), A average speed of movement along the entire route.
The problem of finding the average speed during uniformly accelerated motion was first solved by Galileo. In his research, he used a graphical method to describe movement.
According to Galileo's theory, if the speed of a body during uniformly accelerated motion increases from 0 to a certain value V, then the average speed will be equal to half the achieved speed:
A similar formula is valid for movement with decreasing speed. If it decreases from some initial value V 0 to 0, then the average speed of such movement is equal to
The results obtained can be illustrated using a speed graph. So, for example, to find the average speed of movement, which corresponds to the graph in Figure 5, we must find half of 6 m/s. The result is 3 m/s. This is the average speed of the movement in question.
1. Who is the author of the first theory of uniformly accelerated motion? 2. What is the speed of a body during uniformly accelerated motion from a state of rest? 3. Using the graph shown in Figure 5, determine the speed of the body 2 s after the start of movement. 4. Using the graph shown in Figure 6, determine the average speed of the body.
S.V. Gromov, N.A. Rodina, Physics 8th grade
Submitted by readers from Internet sites
Fundamentals of physics, online physics lessons, physics program, physics abstracts, physics textbooks, physics at school, physics tests, physics curriculum
Lesson content lesson notes supporting frame lesson presentation acceleration methods interactive technologies Practice tasks and exercises self-test workshops, trainings, cases, quests homework discussion questions rhetorical questions from students Illustrations audio, video clips and multimedia photographs, pictures, graphics, tables, diagrams, humor, anecdotes, jokes, comics, parables, sayings, crosswords, quotes Add-ons abstracts articles tricks for the curious cribs textbooks basic and additional dictionary of terms other Improving textbooks and lessonscorrecting errors in the textbook updating a fragment in a textbook, elements of innovation in the lesson, replacing outdated knowledge with new ones Only for teachers perfect lessons calendar plan for the year; methodological recommendations; discussion program Integrated LessonsIn rectilinear uniformly accelerated motion the body
- moves along a conventional straight line,
- its speed gradually increases or decreases,
- over equal periods of time, the speed changes by an equal amount.
For example, a car starts moving from a state of rest along a straight road, and up to a speed of, say, 72 km/h it moves uniformly accelerated. When the set speed is reached, the car moves without changing speed, i.e. uniformly. With uniformly accelerated motion, its speed increased from 0 to 72 km/h. And let the speed increase by 3.6 km/h for every second of movement. Then the time of uniformly accelerated movement of the car will be equal to 20 seconds. Since acceleration in SI is measured in meters per second squared, acceleration of 3.6 km/h per second must be converted into the appropriate units. It will be equal to (3.6 * 1000 m) / (3600 s * 1 s) = 1 m/s 2.
Let's say that after some time of driving at a constant speed, the car began to slow down to stop. The movement during braking was also uniformly accelerated (over equal periods of time, the speed decreased by the same amount). In this case, the acceleration vector will be opposite to the velocity vector. We can say that the acceleration is negative.
So, if the initial speed of a body is zero, then its speed after a time of t seconds will be equal to the product of acceleration and this time:
When a body falls, the acceleration of gravity “works”, and the speed of the body at the very surface of the earth will be determined by the formula:
If you know the current speed of the body and the time it took to develop such speed from a state of rest, then you can determine the acceleration (i.e. how quickly the speed changed) by dividing the speed by the time:
However, the body could begin uniformly accelerated motion not from a state of rest, but already possessing some speed (or it was given an initial speed). Let's say you throw a stone vertically down from a tower using force. Such a body is subject to a gravitational acceleration equal to 9.8 m/s 2 . However, your strength gave the stone even more speed. Thus, the final speed (at the moment of touching the ground) will be the sum of the speed developed as a result of acceleration and the initial speed. Thus, the final speed will be found according to the formula:
However, if the stone was thrown upward. Then its initial speed is directed upward, and the acceleration of free fall is directed downward. That is, the velocity vectors are directed in opposite directions. In this case (as well as during braking), the product of acceleration and time must be subtracted from the initial speed:
From these formulas we obtain the acceleration formulas. In case of acceleration:
at = v – v 0
a = (v – v 0)/t
In case of braking:
at = v 0 – v
a = (v 0 – v)/t
In the case when a body stops with uniform acceleration, then at the moment of stopping its speed is 0. Then the formula is reduced to this form:
Knowing the initial speed of the body and the braking acceleration, the time after which the body will stop is determined:
Now let's print formulas for the path that a body travels during rectilinear uniformly accelerated motion. The graph of speed versus time for rectilinear uniform motion is a segment parallel to the time axis (usually the x axis is taken). The path is calculated as the area of the rectangle under the segment. That is, by multiplying speed by time (s = vt). With rectilinear uniformly accelerated motion, the graph is a straight line, but not parallel to the time axis. This straight line either increases in the case of acceleration or decreases in the case of braking. However, path is also defined as the area of the figure under the graph.
In rectilinear uniformly accelerated motion, this figure is a trapezoid. Its bases are a segment on the y-axis (speed) and a segment connecting the end point of the graph with its projection on the x-axis. The sides are the graph of speed versus time itself and its projection onto the x-axis (time axis). The projection onto the x-axis is not only the side side, but also the height of the trapezoid, since it is perpendicular to its bases.
As you know, the area of a trapezoid is equal to half the sum of the bases and the height. The length of the first base is equal to the initial speed (v 0), the length of the second base is equal to the final speed (v), the height is equal to time. Thus we get:
s = ½ * (v 0 + v) * t
Above was given the formula for the dependence of the final speed on the initial and acceleration (v = v 0 + at). Therefore, in the path formula we can replace v:
s = ½ * (v 0 + v 0 + at) * t = ½ * (2v 0 + at) * t = ½ * t * 2v 0 + ½ * t * at = v 0 t + 1/2at 2
So, the distance traveled is determined by the formula:
s = v 0 t + at 2 /2
(This formula can be arrived at by considering not the area of the trapezoid, but by summing up the areas of the rectangle and right triangle into which the trapezoid is divided.)
If the body begins to move uniformly accelerated from a state of rest (v 0 = 0), then the path formula simplifies to s = at 2 /2.
If the acceleration vector was opposite to the speed, then the product at 2 /2 must be subtracted. It is clear that in this case the difference between v 0 t and at 2 /2 should not become negative. When it becomes zero, the body will stop. A braking path will be found. Above was the formula for the time until a complete stop (t = v 0 /a). If we substitute the value t into the path formula, then the braking path is reduced to the following formula.
1) Analytical method.We consider the highway to be straight. Let's write down the equation of motion of a cyclist. Since the cyclist moved uniformly, his equation of motion is:
(we place the origin of coordinates at the starting point, so the initial coordinate of the cyclist is zero).
The motorcyclist was moving at uniform acceleration. He also started moving from the starting point, so his initial coordinate is zero, the initial speed of the motorcyclist is also zero (the motorcyclist began to move from a state of rest).
Considering that the motorcyclist started moving later, the equation of motion for the motorcyclist is:
In this case, the speed of the motorcyclist changed according to the law:
At the moment when the motorcyclist caught up with the cyclist, their coordinates are equal, i.e. or:
Solving this equation for , we find the meeting time:
This is a quadratic equation. We define the discriminant:
Determining the roots:
Let's substitute numerical values into the formulas and calculate:
We discard the second root as not corresponding to the physical conditions of the problem: the motorcyclist could not catch up with the cyclist 0.37 s after the cyclist started moving, since he himself left the starting point only 2 s after the cyclist started.
Thus, the time when the motorcyclist caught up with the cyclist:
Let's substitute this time value into the formula for the law of change in speed of a motorcyclist and find the value of his speed at this moment:
2) Graphic method.
On the same coordinate plane we build graphs of changes over time in the coordinates of the cyclist and motorcyclist (the graph for the cyclist’s coordinates is in red, for the motorcyclist – in green). It can be seen that the dependence of the coordinate on time for a cyclist is a linear function, and the graph of this function is a straight line (the case of uniform rectilinear motion). The motorcyclist was moving with uniform acceleration, so the dependence of the motorcyclist’s coordinates on time is a quadratic function, the graph of which is a parabola.
Ticket 1.
Question. Types of mechanical movement. Velocity and acceleration of a body during uniformly accelerated linear motion.
Mechanical movement – change in the position of a body in space relative to other bodies over time. The movement of the train relative to the ground, the movement of the passenger relative to the train, etc.
Speed– vector physical a quantity that characterizes the speed of movement and its direction of a material point in space.
Trajectory- This is the line along which the body moves.
Moving is the shortest distance between the start and end points.
Material point is a body whose dimensions can be neglected.
Path– this is the length of the territory covered by the body in a period of time.
There are several types of mechanical movement:
1) Uniform linear movement- this is a movement in which a body makes equal movements at any equal intervals of time.
Example: If a driver is driving in a straight line while maintaining a constant speed.
2) Uneven linear movement - This is a movement with variable speed.
Uniformly accelerated motion - This is a movement in which the speed of a body changes equally over any equal intervals of time. (velocity and acceleration are directed in the same direction)
Example: A flower pot falling from a balcony.
Equally slow motion - This is the movement of a body with negative acceleration, i.e. with such movement the body uniformly slows down. (speed and acceleration are in opposite directions)
Example: Movement of a stone thrown vertically upward.
3) Curvilinear movement - This is a movement whose trajectory is a curved line.
Example: the movement of the planets, the end of the clock hand on the dial.
With uniformly accelerated linear motion, the speed of a body increases over time.
The acceleration of a body during uniformly accelerated motion is a vector physical quantity equal to the ratio of the change in the speed of the body to the period of time during which this change occurred.
The velocity and acceleration vectors are directed in the same direction.
Question. Electromagnetic radiation of various ranges. Properties and applications of these radiations.
Electromagnetic radiation are interconnected and cannot exist without each other alternating electric and magnetic fields propagating in space at a finite speed. They have wave and quantum properties.
Radio waves.
Frequency: 3 kHz to 300 GHz.
Obtained using an oscillatory circuit and macroscopic vibrators.
Properties: Radio waves of different frequencies and with different wavelengths are absorbed and reflected differently by media, and exhibit diffraction and interference properties.
Application: Radio communications, television, radar.
Infrared radiation (thermal).
Frequency: 1.5 THz - 405 THz.
Wavelength:
· short: 0.74-2.5 microns;
medium: 2.5-50 microns;
· long: 50-2000 microns.
Emitted by atoms and molecules of matter. Infrared radiation is emitted by all bodies at any temperature. A person emits electromagnetic waves with a wavelength λ= l.9*10-6 m.
Properties:
1. Passes through some opaque bodies, also through rain, haze, snow.
2. Produces a chemical effect on photographic plates.
3. Absorbed by a substance, it heats it.
4. Causes an internal photoelectric effect in germanium.
5. Invisible.
6. Capable of interference and diffraction phenomena.
Recorded by thermal, photoelectric and photographic methods.
Application: Obtain images of objects in the dark, night vision devices (night binoculars), and fog. Used in forensics, physiotherapy, and in industry for drying painted products, building walls, wood, and fruit.
Visible radiation.
This is part of the solar radiation spectrum (from red to violet).
Frequency: 4*1014-8*1014Hz
Properties: Reflects, refracts, affects the eye, is capable of the phenomena of dispersion, interference, diffraction.
Ultraviolet radiation.
Frequency: 10 13 -10 16 Hz.
Sources: gas-discharge lamps with quartz tubes (quartz lamps).
Emitted by all solids with t>1000ºС, as well as luminous mercury vapor.
Properties: High chemical activity (decomposition of silver chloride, glow of zinc sulfide crystals), invisible, high penetrating ability, kills microorganisms, in small doses has a beneficial effect on the human body (tanning), but in large doses has a negative biological effect: changes in cell development and metabolism, effects on the eyes.
Application: In medicine, in industry.
X-rays.
Emitted during high acceleration of electrons, for example their deceleration in metals. Obtained using an X-ray tube: electrons in a vacuum tube (p = 10-3-10-5 Pa) are accelerated by an electric field at high voltage, reaching the anode, and are sharply decelerated upon impact. When braking, electrons move with acceleration and emit electromagnetic waves with a short length (from 100 to 0.01 nm).
Properties: Interference, X-ray diffraction on a crystal lattice, high penetrating power. Irradiation in large doses causes radiation sickness.
Application: In medicine (diagnosis of diseases of internal organs), in industry (control of the internal structure of various products, welds).
Gamma radiation (gamma rays).
A type of electromagnetic radiation with an extremely short wavelength - less than 2·10−10 m - and, as a result, pronounced corpuscular and weakly expressed wave properties
Gamma radiation has great penetrating power, i.e. it can pass through large thicknesses of matter.
Gamma radiation is used in technology (for example, flaw detection), radiation chemistry (for initiating chemical transformations, for example, during polymerization), agriculture and the food industry (mutations for the generation of economically useful forms, sterilization of products), in medicine (sterilization premises, objects, radiation therapy), etc.
Ticket 2.
Question. Newton's laws. Their manifestation, accounting and use.
Newton's laws.
1) There are inertial reference systems relative to which a body, in the absence of external forces acting on it (or with their mutual compensation), maintains a state of rest or uniform linear motion.
2) The acceleration of a body is directly proportional to the resultant of all forces applied to the body.
3) Material points interact with each other by forces of the same nature, directed along the straight line connecting these points, equal in magnitude and opposite in direction
All classical mechanics is based on these laws.
Newton's laws are the basic laws of mechanics. From these the equations of motion of mechanical systems can be derived. However, not all laws of mechanics can be derived from Newton's laws. For example, the law of universal gravitation or Hooke's law are not consequences of Newton's three laws.
Newton's laws make it possible to explain the patterns of motion of planets and their natural and artificial satellites. Otherwise, they make it possible to predict the trajectories of planets, calculate the trajectories of spacecraft and their coordinates at any given time. Under terrestrial conditions, they make it possible to explain the flow of water, the movement of numerous and varied vehicles (the movement of cars, ships, airplanes, rockets). For all these movements, bodies and forces, Newton's laws are valid.
Question. Experimental methods for recording ionizing radiation.
Wilson chamber.
Along the path of charged particles, tracks of condensed supersaturated vapor are formed on the ions. Using a cloud chamber, energy, speed, and charge are determined. Consists of a glass plate, piston and valve.
Operating principle: The working volume of the chamber is filled with gas, which contains saturated steam. When the piston moves down quickly, the gas in the volume expands and cools, becoming supersaturated. When a particle flies through this space, creating ions along its path, then droplets of condensed vapor are formed on these ions. A particle track appears in the chamber in the form of a strip of fog.
Geiger counter. It consists of a cathode, a thin thread stretched along the axis, and an anode.
Operating principle: A gas mixture is pumped into a sealed cylinder with two electrodes. A high voltage is applied to the electrodes. The appearance of particles arriving from outside leads to the fact that primary electrons, accelerated in the corresponding field, begin to ionize other molecules of the gaseous medium. As a result, under the influence of an electric field, an avalanche-like creation of new electrons and ions occurs, which sharply increase the conductivity of the electron-ion cloud. A discharge occurs in the gas environment of the Geiger counter.
Using a Geiger counter, the fact that electrons and photons enter the tube is recorded.
Bubble chamber. Consists of a sealed chamber filled with liquefied gas.
Operating principle: The working volume is filled with liquid hydrogen heated almost to boiling and under high pressure. The liquid is transferred to a superheated state by sharply reducing the pressure. A charged particle forms a chain of ions along its path, which leads to a sudden boiling of the liquid. Vapor bubbles appear along the particle trajectory. Based on the photograph of the track, alpha, beta, and gamma particles are distinguished.
Scintillation counter.
The main elements are: a substance that luminesces under the influence of charged particles (scintillator) and a photomultiplier tube (PMT)
Operating principle: The particle causes a flash of light in the phosphor, which is detected by a photomultiplier. Heavy particles are detected.
Ticket 3.
Ideal gas.
The main differences between an ideal gas and a real gas:
1) Particles of an ideal gas are spherical bodies of very small sizes, practically material points.
2) There is no intermolecular interaction force between particles.
3) The collision of particles is absolutely elastic.
An ideal gas does not exist in nature.
A qualitative explanation of gas pressure is that ideal gas molecules, when colliding with the walls of a container, interact with them according to the laws of mechanics as elastic bodies.
Based on the use of the basic principles of molecular kinetic theory, an equation was obtained that made it possible to calculate gas pressure if the density of the substance and speed were known.
Molecular kinetic theory - a theory that arose in the 19th century and considers the structure of matter, mainly gases, from the point of view of three main approximately correct provisions:
· all bodies consist of particles: atoms and molecules;
· particles are in continuous chaotic motion (thermal);
· particles interact with each other through absolutely elastic collisions.
The beginning of the formation of MCT was the theory of M.V. Lomonosov.
On the basis of MCT, a number of branches of modern physics have been developed, in particular, physical kinetics and statistical mechanics.
The basic MKT equation connects macroscopic parameters (pressure, volume, temperature) of a thermodynamic system with microscopic ones (mass of molecules, average speed of their movement).
Temperature - it is a measure of the average kinetic energy of molecules.
The limiting temperature at which the pressure of an ideal gas vanishes at a fixed volume is called absolute zero temperature. Absolute zero temperature: -273̊ C. It is convenient to count the temperature from absolute zero. This is how the absolute temperature scale is constructed.
Absolute temperature– temperature measured from absolute zero.
The average kinetic energy of translational motion of gas molecules is proportional to temperature. The higher the temperature, the faster the molecules move.
Avogadro's Law: Equal volumes of gases at the same temperatures and pressures contain the same number of molecules.
Ticket 4.
Bohr's postulates.
1 postulate. There are special, stationary states of the atom, in which the atom does not emit energy, while the electrons in the atom move with acceleration. Each stationary state corresponds to a certain energy.
2nd postulate. The emission of light occurs when an atom transitions from a stationary state with higher energy to a stationary state with lower energy. The energy of the emitted photon is equal to the energy difference between the stationary states.
In 1914, Frank and Hertz conducted an experiment confirming Bohr's theory: atoms of a rarefied gas were bombarded with slow electrons, followed by a study of the distribution of electrons in absolute velocity values before and after the collision. During an elastic impact, the distribution should not change, since only the direction of the velocity vector changes. The results showed that when electron speeds are less than a certain critical value, the collisions are elastic, and at a critical speed the collisions become inelastic, the electrons lose energy, and the gas atoms go into an excited state. With a further increase in speed, the impacts again became elastic until a new critical speed was reached. The observed phenomenon allowed us to conclude that the atom may either not absorb energy at all, or absorb in quantities equal to the energy difference of stationary states.
Ticket 5.
Spectral analysis.
The main property of spectra is that the wavelengths of the line spectrum of a substance depend only on the properties of the atoms of this substance, but are completely independent of the method of excitation of the luminescence of atoms. Atoms of any chemical elements give a spectrum that is not similar to the spectra of all other elements. This is what it is based on spectral analysis– method for determining chemical composition of a substance according to its spectrum. Currently, the spectra of all atoms have been determined and tables of the spectra have been compiled. With the help of spectral analysis, many new elements were discovered: rubidium, cesium, etc. It was with the help of spectral analysis that the chemical composition of the Sun and stars was learned. Helium was first discovered in the Sun and only then in the Earth's atmosphere. Spectral analysis is also used to determine the chemical composition of ores and minerals.
Ticket 6.
Law of conservation of momentum.
The forces arising as a result of the interaction of a body belonging to the system with a body not belonging to it are called external forces.
The forces arising as a result of the interaction of bodies belonging to the system are called internal forces.
The momentum of a system of bodies can only be changed by external forces.
The law of conservation of momentum is formulated as follows: if the sum of external forces is zero, then the momentum of the system is conserved.
Momentum is also conserved in an isolated system, because in this system the bodies are not acted upon by external forces at all.
Jet propulsion.
Under jet propulsion understand the movement of a body that occurs when a certain part is separated with a certain speed relative to it. In this case, there arises Reactive force.
For example, you can inflate a child's rubber ball and release it. The ball will fly quickly. The reaction force will act as long as the outflow of air continues.
Jet engines are now widely used. Not only missiles, but also most modern aircraft are equipped with them.
Any jet engine must have at least two components:
· Combustion chamber - it is where the chemical energy of the fuel is released and converted into thermal energy of gases.
· Jet nozzle - in which the thermal energy of gases is converted into their kinetic energy when gases flow out of the nozzle at high speed, thereby creating jet thrust.
The main technical parameter characterizing a jet engine is traction- the force that the engine develops in the direction of movement of the device.
K. E. Tsiolkovsky - founder of the theory of space flight. Scientific proof of the possibility of using a rocket for flights into outer space, beyond the Earth's atmosphere and to other planets of the solar system was first given by the Russian scientist and inventor Konstantin Eduardovich Tsiolkovsky (1857-1935). In his work “Exploration of World Spaces by Jet Instruments,” published in 1903, a formula was derived that established the relationship between the speed of the rocket, the speed of gas flow, the mass of the rocket and the mass of the fuel. Tsiolkovsky theoretically substantiated the possibility of creating a rocket capable of accelerating to a speed of 8 km/s and flying into outer space. He proposed using liquid hydrogen as fuel for such a rocket, and liquid oxygen as an oxidizer. The design of a liquid rocket, according to K. E. Tsiolkovsky, is presented in Figure 62. In 1929, K. E. Tsiolkovsky developed the idea of creating “space rocket trains”. The theoretical works of K. E. Tsiolkovsky were more than half a century ahead of the level of technological development. These works served as the basis for the creation of modern theoretical and practical astronautics.
Successes of the USSR in space exploration. The ideas of K. E. Tsiolkovsky about the creation of “space rocket trains” - multi-stage rockets - were implemented by Soviet scientists and technicians under the leadership of the outstanding Soviet scientist, Academician Sergei Pavlovich Korolev (1907-1966).
The world's first artificial Earth satellite was launched by rocket in the Soviet Union on October 4, 1957.
On April 12, 1961, citizen of the Soviet Union Yuri Alekseevich Gagarin (1934-1968) made the world's first flight in outer space on the Vostok spacecraft.
Soviet space rockets delivered soil samples from the surface of the Moon to Earth, soft-landed automatic interplanetary stations on the surface of Venus and Mars, and launched long-term orbital stations into low-Earth orbit.
Flights of spacecraft with astronauts on board, automatic interplanetary stations and artificial Earth satellites are used both for scientific research in near-Earth and interplanetary space, and for solving practical problems of the national economy.
Using satellites and automatic interplanetary stations, the composition and structure of the Earth's atmosphere at high altitudes, the chemical composition and physical properties of the atmosphere of Venus and Mars were studied, and images of the surface of the Moon, Venus and Mars were obtained.
Molniya communication satellites, through Orbit ground stations, broadcast television programs and telephone communications at any distance within our country.
Meteorological satellites are used to study processes occurring in the earth's atmosphere and make weather forecasts.
Special satellites help ships and aircraft determine their coordinates. Studies of the surface of continents and oceans, carried out by astronauts during flights at orbital stations, make it possible to assess and clarify natural resources in various regions of the globe.
Question 2. Electric current in a vacuum. Thermionic emission. Application of vacuum devices.
Vacuum- a medium that contains gas at a pressure significantly lower than atmospheric pressure.
To create a current in a vacuum, a special source of charged particles is required. The action of such a source is usually based on thermionic emission.
Thermionic emission- the phenomenon of electrons being ejected from a metal at high temperature.
The phenomenon of thermionic emission leads to the fact that a heated metal electrode, unlike a cold one, continuously emits electrons. The electrons form an electron cloud around the electrode. The electrode becomes positively charged, and under the influence of the electric field of the charged cloud, electrons from the cloud are partially returned to the electrode.
When the electrodes are connected to a current source, an electric field arises between them.
One-way conductivity was previously widely used in electronic devices with two electrodes - vacuum diodes, which, like semiconductor diodes, served to rectify electric current. However, at present, vacuum diodes are practically not used.
Ticket 7.
Ticket 8.
Development of communications.
Until relatively recently, intercity telephone communications was carried out exclusively by wire.
Currently, cable and radio relay lines are being increasingly used, and the level of communication automation is increasing.
Ultrashort (decimeter and centimeter) waves are used in radio relay communication lines. These waves travel within line of sight.
Fiber optic communication lines are becoming increasingly popular, allowing the transfer of large amounts of information. The transmission process is based on multiple reflections of a laser beam propagating through a thin tube (fiber).
Advances in the field of space radio communications made it possible to create a new communication system called Orbita. This system uses relay communication satellites.
Powerful and reliable systems have been created to provide television broadcasting to the regions of Siberia and the Far East. They allow telephone and telegraph communication with remote areas of our country.
Such relatively old means of communication as the telegraph and phototelegraph are also being improved and found new applications.
A Unified Automated Communication System is being created in our country. In this regard, various technical means of communication are developing, improving and finding new areas of application.
Ticket 9.
Ticket 11.
Ticket 12.
Ticket 13.
Ticket 14.
A value equal to the ratio of the work done by external forces when moving a point positive charge along the entire circuit, including the current source, to the charge is called the electromotive force of the current source.
Ohm's law is a formula that shows the dependence of the main characteristics of an electrical circuit, namely voltage (electromotive force), electric current (flow of charged particles) and resistance (opposition to the flow of electrons in a solid conductor).
Ohm's law for a complete circuit sounds like this: the current strength in an electrical circuit will be directly proportional to the voltage applied to this circuit, and inversely proportional to the sum of the internal resistance of the power source and the total resistance of the entire circuit.
Using Ohm's Law for a complete circuit, you can calculate the total voltage across the power supply terminals, the total current (consumed by the circuit), and the total resistance of the entire circuit.
I = U ⁄ r + R
Ticket 15.
Ticket 16.
Ticket 17.
Ticket 18.
Ticket 19.
1 question. Photoelectric effect and its laws. Explanation of the photoelectric effect and its application .
Photo effect- This is the phenomenon of the emission of electrons by a substance under the influence of light.
Stoletov's laws for the photoelectric effect:
Formulation of the 1st law of the photoelectric effect: The strength of the photocurrent is directly proportional to the density of the light flux.
According to the 2nd law of the photoelectric effect, the maximum kinetic energy of electrons ejected by light increases linearly with the frequency of light and does not depend on its intensity.
3rd law of the photoelectric effect: for each substance there is a red limit of the photoelectric effect, that is, the minimum frequency of light (or maximum wavelength λ0) at which the photoelectric effect is still possible, and if , then the photoelectric effect no longer occurs.
The theoretical explanation of these laws was given in 1905 by Einstein. According to him, electromagnetic radiation is a stream of individual quanta (photons) with energy hν each, where h- Planck's constant. With the photoelectric effect, part of the incident electromagnetic radiation is reflected from the metal surface, and part penetrates into the surface layer of the metal and is absorbed there. Having absorbed a photon, the electron receives energy from it and, performing work function φ, leaves the metal: where is the maximum kinetic energy that the electron has when leaving the metal.
Application.
Devices based on the photoelectric effect are called photocells. The simplest such device is a vacuum photocell. The disadvantages of such a photocell are: low current, low sensitivity to long-wave radiation, difficulty in manufacturing, impossibility of use in alternating current circuits. It is used in photometry to measure luminous intensity, brightness, illumination, in cinema for sound reproduction, in phototelegraphs and photophones, in the management of production processes.
There are semiconductor photocells in which the concentration of current carriers changes under the influence of light. They are used in the automatic control of electrical circuits (for example, in subway turnstiles), in alternating current circuits, as non-renewable current sources in watches, microcalculators, the first solar cars are being tested, and are used in solar batteries on artificial Earth satellites, interplanetary and orbital automatic stations .
The phenomenon of the photoelectric effect is associated with photochemical processes occurring under the influence of light in photographic materials.
Question 2 . Deformations of solids and their types. Hooke's law. Accounting and application of deformation in technology.
Hooke's law
The deformation that occurs in an elastic body (spring, rod, console, beam, etc.) is proportional to the force applied to this body.
Ticket number 20.
Composition of the atomic nucleus.
The nucleus of an atom consists of nucleons, which are divided into protons and neutrons.
A is the number of nucleons, i.e. protons + neutrons (or atomic mass)
Z- number of protons (equal to the number of electrons)
N is the number of neutrons (or atomic number)
Isotopes
Isotopes- varieties of atoms (and nuclei) of a chemical element that have the same atomic (ordinal) number, but at the same time different mass numbers. All chemical isotopes elements are radioactive.
Examples of hydrogen isotopes (H): Deuterium, Tritium, Quadium, etc.
Binding energy of atomic nuclei.
Atomic nuclei are strongly bound systems of a large number of nucleons.
To completely split the nucleus into its component parts and remove them at large distances from each other, it is necessary to expend a certain amount of work A.
Energy of communication they call energy equal to the work that must be done to split a nucleus into free nucleons.
E connection = - A
According to the law of conservation, the binding energy is simultaneously equal to the energy that is released during the formation of a nucleus from individual free nucleons.
Ticket 21.
Ticket 22.
INDUCTANCE
Electric current creates its own magnetic field. The magnetic flux through the circuit is proportional to the magnetic field induction (Ф ~ B), the induction is proportional to the current strength in the conductor
(B ~ I), therefore the magnetic flux is proportional to the current strength (Ф ~ I).
The self-induction emf depends on the rate of change of current in the electrical circuit and on the properties of the conductor
(size and shape) and on the relative magnetic permeability of the medium in which the conductor is located.
A physical quantity showing the dependence of the self-induction emf on the size and shape of the conductor and on the environment in which the conductor is located is called the self-induction coefficient or inductance. 
Inductance- physical a value numerically equal to the self-inductive emf that occurs in the circuit when the current changes by 1 Ampere in 1 second.
Inductance can also be calculated using the formula: 
where Ф is the magnetic flux through the circuit, I is the current strength in the circuit.
SI units of inductance: 
The inductance of the coil depends on:
the number of turns, the size and shape of the coil and the relative magnetic permeability of the medium
(core possible).
SELF-INDUCTION EMF
The self-inductive emf prevents the current from increasing when the circuit is turned on and the current from decreasing when the circuit is opened.
ENERGY OF THE MAGNETIC FIELD OF CURRENT
Around a current-carrying conductor there is a magnetic field that has energy.
Where does it come from? The current source included in the electrical circuit has a reserve of energy.
At the moment of closing the electrical circuit, the current source spends part of its energy to overcome the action of the self-inductive emf that arises. This part of the energy, called the current’s own energy, goes to the formation of a magnetic field.
The energy of the magnetic field is equal to the intrinsic energy of the current.
The self-energy of the current is numerically equal to the work that the current source must do to overcome the self-induction emf in order to create a current in the circuit.
The energy of the magnetic field created by the current is directly proportional to the square of the current.
Where does the magnetic field energy go after the current stops? - stands out (when the circuit is opened with a sufficiently large current, a spark or arc may occur)
Ticket number 23
SERIAL CONNECTION
with series connection of resistances:
1. the current strength in all series-connected sections of the circuit is the same
2. voltage in a circuit consisting of several sections connected in series,
equal to the sum of stresses in each section
3. resistance of a circuit consisting of several sections connected in series,
equal to the sum of the resistances of each section
4. the work of electric current in a circuit consisting of sections connected in series,
equal to the sum of work in individual areas
5. the power of electric current in a circuit consisting of sections connected in series,
equal to the sum of the capacities in individual sections
PARALLEL CONNECTION
Calculation of electrical circuit parameters
with parallel connection of resistances:
1. the current strength in the unbranched section of the circuit is equal to the sum of the current strengths
in all parallel connected sections
3. When connecting resistances in parallel, the reciprocal values of the resistance are added:
(R - conductor resistance,
1/R - electrical conductivity of the conductor)
If only two resistances are connected in parallel in a circuit, then O:
(with a parallel connection, the total resistance of the circuit is less than the smaller of the included resistances)
4. the work of electric current in a circuit consisting of parallel connected sections,
equal to the sum of work in individual areas:
5. the power of electric current in a circuit consisting of parallel connected sections,
equal to the sum of the capacities in individual areas:
For two resistances:
those. The greater the resistance, the less current it contains.
Ticket number 24
Electromagnetic field
1. An alternating magnetic field creates a vortex electric field.
Electromagnetic field
This is a special form of matter - a combination of electric and magnetic fields.
Alternating electric and magnetic fields exist simultaneously and form a single electromagnetic field.
Electromagnetic wave
AND 
an electromagnetic field varying in time and propagating in space (vacuum) with a speed of 3∙10 8 m/s forms electromagnetic wave.
The finite speed of propagation of the electromagnetic field leads to the fact that electromagnetic oscillations in space propagate in the form of waves.
Electromagnetic wave is transverse.
N 
The direction of the speed of the electromagnetic wave coincides with the direction of movement of the right screw when turning the handle of the vector gimlet 
to vector 
.
Vector values And coincide in phase (far from the antenna).
Wave properties
1. Reflection, refraction, interference, diffraction, polarization.
2. Pressure on a substance.
3. Absorption by the environment.
4. The final speed of propagation in a vacuum.
5. Causes the phenomenon of photoelectric effect.
6. The speed in the medium decreases.