Questions.

1. Does gravity act on a body thrown upward during its ascent?

The force of gravity acts on all bodies, regardless of whether it is thrown up or is at rest.

2. With what acceleration does a body thrown up move in the absence of friction? How does the speed of the body change in this case?

3. What determines the maximum height of lift of a body thrown upward in the case when air resistance can be neglected?

The lift height depends on the initial speed. (For calculations, see previous question).

4. What can be said about the signs of the projections of the vectors of the instantaneous velocity of the body and the acceleration of gravity during the free upward movement of this body?

When a body moves freely upward, the signs of the projections of the velocity and acceleration vectors are opposite.

5. How were the experiments depicted in Figure 30 carried out, and what conclusion follows from them?

For a description of the experiments, see pages 58-59. Conclusion: If only gravity acts on a body, then its weight is zero, i.e. it is in a state of weightlessness.

Exercises.

1. A tennis ball was thrown vertically upward with an initial speed of 9.8 m/s. After what period of time will the speed of the rising ball decrease to zero? How much movement will the ball make from the point of throw?

Very little has been written about this in the literature, so the proposed development, lying in my archives, is in some sense unique.

The signs of the Zodiac only resemble a ruler with divisions, along which you can follow the movement of the planets. In fact, these are voluminous and complex entities that one would like to call alive - each with its own character and characteristics. In the Zodiac, each sign describes its own stage of the cyclical process - from its beginning in Aries to its completion in Pisces. Each sign is a phase of the Universal Cycle, which I wrote about in my book “Cosmic Rhythms of Life”.

Therefore, the signs of the Zodiac can be compared with the most important functions of the body and with the systems that perform these functions. Moreover, positive or masculine signs (Aries, Gemini, Leo, Libra, Sagittarius, Aquarius) are associated with a group of functions that can be called command-motor. Their role is to quickly respond to emerging stimuli, determine a goal in the external world and control organs and parts of the body to achieve this goal.

But negative or female signs are associated mainly with the nutritional and construction group of functions. The area of ​​their concerns is limited to the boundaries of the body, and the main goal is how to manage the economy within these limits, to ensure the normal state of the internal environment, the availability of sufficient reserves, the growth of necessary tissues and organs and the destruction and removal from the body of everything unnecessary and harmful.

Role Aries- immediate response to external and internal signals and issuing “orders” to the body. Therefore, the sign of Aries is functionally connected primarily with the central nervous system, as well as with the somatic part of the nervous system, focused on the interaction of the body with the external environment. Probably, the sphere of influence of Aries should include part of the hormonal system that supports the body's reaction to external stimuli (remember, for example, adrenaline), as well as the striated muscles - the main executor of orders.

Please note that the functional components of Aries do not coincide with its anatomical projections. Let's say the spinal cord “territorially” belongs to Leo, but functionally to Aries. And if in the future we see that a certain planet creates problems in a particular sign, then on the basis of anatomical correspondence we will be able to judge in which area of ​​the body this problem is most likely to manifest itself, and on the basis of functional correspondence - what functions of the body (and the ones that implement them) organ systems) will be involved.

If the sign of Aries can be compared to the commander-in-chief of the body, then Taurus- this, of course, is the deputy for the rear. The main task of the Taurus sign is to provide the body with everything it needs, primarily nutrients. It is in charge of warehouses - the body's fat reserves - and that part of the digestive system that is associated with the absorption of food - the oral cavity, pharynx, tongue, esophagus. All organs that form any kind of reserves in the body (for example, the liver) are functionally connected with Taurus.

Twins provide communication, receipt and transmission of information - both within the body and with the external environment. Their “department” includes all kinds of receptors and signal-transmitting nerve fibers. The circulatory system performs many different functions, but if we consider it as a carrier of hormones (original orders, that is, chemically encrypted information), then it can also be considered as one of the projections of the sign of Gemini. Another task of Gemini, also related to the circulatory system - but not only with it - is the transportation of various substances - both useful and harmful - in the interests of all other systems.

Sign Cancer- This is the “kitchen” of the body. Its task is to absorb nutrients entering the body. The etymology of the word “assimilation” is interesting - it comes from the word “own”. Cancer receives from Taurus substances that come from the outside world - in general, foreign ones. It breaks them down, processes them, and they are assimilated - they become their own, suitable as bricks for the construction of their own organism. The construction function - the creation of new cells, the growth of organs and tissues - is also under the control of Cancer. This sign is like the “chief manager” and supplier of materials for all growth processes in the body.

Lion- the manager of the main energy station of the body - the heart, as well as the largest vessels adjacent to it, forming the central, vital part of the circulatory system. Leo also refers to the intangible, but nevertheless very important energy reservoir of vitality, or vital energy in the body. Perhaps this mystical formation is located in the solar plexus area. Both a person’s creative abilities and his ability to give life to another human being (thus sharing his energy) depend on how much energy there is.

Sign Virgo- a kind of “dry cleaning” of the body. Its task is to separate the “wheat from the chaff”, leaving in the body everything that is necessary and useful and getting rid of what is harmful or simply unnecessary. A similar process of discrimination and separation constantly occurs in our intestines, but not only in it. The liver, kidneys, spleen - all these organs determine the presence of unnecessary substances in the body and separate them from useful substances, thus fulfilling the function of the Virgo sign.

Scales The name itself indicates the main function of this zodiac sign - maintaining the balance of various processes in the body. Our body is very vulnerable and is able to function only in a narrow range of temperatures, pressures, and concentrations of chemicals. And in order to ensure the constancy of the internal environment of the body (homeostasis), it is necessary to constantly make the finest adjustments - including taking into account the state of the external environment. All this is very reminiscent of scales, the axis of which is motionless, and the bowls are constantly oscillating. In addition to the kidneys - the traditional projection of the sign of Libra - their responsibility includes part of the hormonal system that ensures homeostasis, possibly the vestibular apparatus, and many different subsystems throughout the body, the task of which is to signal an imbalance and take measures to restore it.

Scorpion takes the baton of negative signs from Virgo, and his task is to remove everything unnecessary outside the body. This process involves the urinary system, the rectum - Scorpio's traditional areas of control - but also, apparently, the sweat glands distributed throughout the skin. The reproductive organs ensure the evacuation of the fetus after it is finally formed, and in this sense they are also part of the functional system of Scorpio. If striated muscles correspond to the Aries principle, then smooth muscles, which delay or enhance the passage of various substances in the body, most likely belong to Scorpio.

Sign Sagittarius, is probably associated with the arterial system, which delivers oxygen and nutrients to the most remote corners of the body, and thus ensures constant “burning” - the process of oxidizing nutrients and releasing energy. Here we recall the common astrological association of Sagittarius with missionaries who brought the light of knowledge and faith to the most remote areas of the Earth. It is quite possible that it is Sagittarius (with the help of Libra) who is responsible for the thermoregulation of the body.

Capricorn- the chief administrator of the body, whose task is to maintain the structure and protect the body from environmental influences. The skeleton, skin, and hair are subordinate to him. You may notice that signs opposite each other on the zodiac circle more or less clearly form a complementary pair. Thus, Capricorn “fences off the territory” of the organism, gives it a form, and already within this form Cancer organizes its economy and creates a living environment.

Aquarius- the sign is unusual, and there are many different opinions about its functional correspondence. Much can be understood based on his relationship as a complementary couple with the sign of Leo. If Leo is the very center of the body, then Aquarius is its periphery, which means that this sign is associated with the work of the peripheral parts of both the nervous and circulatory systems. If for Leo (the heart) it is important to “disperse” the blood from the center, then Aquarius remains with the important task of returning blood to the heart - and therefore he is connected with the venous system. The periphery strongly depends on the center, but always has its own opinion - and hence local spasms and circulatory disorders, which are apparently associated with dysfunction of the sign of Aquarius. It is interesting that in astrology Russia is classified as this sign - the country, one might say, the richest in periphery.

In my opinion, it is Aquarius who is responsible for the hematopoietic function, and therefore is connected with the bone marrow, spleen and other organs that provide this function. And if we complete the analogy with Leo, then we can suspect the participation of Aquarius in the formation of germ cells - a process for which Leo supplies energy.

Fish- the last in the sequence of signs of the Zodiac, and their role is largely associated with the completion of everything that other systems of the body have not completed or have overlooked, neutralization, the cessation of the existence of what cannot be, say, given to Scorpio for elimination from the body. This sign is symbolically connected with the world’s oceans, and therefore is responsible for the state of all liquid media in the body. Pisces has a lymphatic system that closes the circulation of fluids and at the same time neutralizes foreign microorganisms. These also include the immune system - the “secret police” of the body.

I would hardly be able to classify in this way everything that can be found in the body, but the general idea should be clear, and by analogy you can always judge to which sign this or that function or subsystem of the body most relates. It should be taken into account that many (and perhaps all) of the most important functions are provided by the interaction of several signs. So, for example, childbirth is ensured by at least Leo (the energetic ability to give life to another organism), Cancer (the construction function that forms the fetus) and Scorpio (the ability to actually give birth to a child).

Laboratory work No. 6 Studying tracks of charged particles using ready-made photographs
Laboratory work No. 1. Study of uniformly accelerated motion without initial speed
Laboratory work No. 2 Measuring the acceleration of gravity
Laboratory work No. 3 Study of the dependence of the period and frequency of free oscillations of a thread pendulum on its length
Laboratory work No. 4 Study of the phenomenon of electromagnetic induction
Laboratory work No. 5 Studying the fission of the nucleus of a uranium atom using photographs of tracks
1. Does a material point have mass? Does it have dimensions?
2. Is a material point a real object or an abstract concept?
3. For what purpose is the concept of “material point” used?
4. In what cases is a moving body usually considered as a material point?
5. Give an example showing that the same body in one situation can be considered a material point, but not in another.
6. During what motion of a body can it be considered as a material point even if the distances it travels are comparable to its dimensions?
7. What is called a material point?
8. In what case can the position of a moving body be specified using a single coordinate axis?
9. What is a frame of reference?
1. How does a body move if other bodies do not act on it?
2. The body moves rectilinearly and uniformly. Does this change its speed?
3. What views regarding the state of rest and motion of bodies existed before the beginning of the 17th century?
4. How does Galileo’s point of view regarding the motion of bodies differ from Aristotle’s point of view?
5. How was the experiment depicted in Figure 19 carried out, and what conclusions follow from it?
6. How is Newton's first law read (in modern formulation)?
7. Which reference systems are called inertial and which are called non-inertial?
8. Is it possible in some cases to consider reference systems associated with bodies that are at rest or moving rectilinearly and uniformly relative to the earth as inertial?
9. Is a reference frame moving with acceleration inertial relative to any inertial frame?
1. What is the reason for the accelerated movement of bodies?
2. Give examples from life indicating that the greater the force applied to the body, the greater the acceleration imparted by this force.
3. Using Figure 20, tell how the experiments were carried out and what conclusions follow from these experiments.
4. How is Newton's second law read? What mathematical formula is it expressed?
5. What can be said about the direction of the acceleration vector and the vector of the resultant forces applied to the body?
6. Express the unit of force in terms of mass and acceleration.
1. Using Figures 21, 22 and 23, tell how the experiments depicted were carried out and what conclusions were drawn based on the results obtained.
2. How is Newton's third law read? How is it written mathematically?
3. What can be said about the acceleration that the Earth receives when interacting with a person walking on it? Justify your departure.
4. Give examples showing that the forces resulting from the interaction of two bodies are identical in nature.
5. Why is it wrong to talk about the balance of forces arising from the interaction of bodies?
1. What is called free fall of bodies?
2. How to prove that the free fall of the ball shown in Figure 27 was uniformly accelerated?
3. What was the purpose of the experiment depicted in Figure 28 and what conclusion follows from it?
4. What is the acceleration of gravity?
5. Why does a piece of cotton wool fall in the air with less acceleration than an iron ball?
6. Who was the first to come to the conclusion that free fall is a uniformly accelerated motion?
1. Does gravity act on a body thrown up during its ascent?
2. With what acceleration does a body thrown up move in the absence of friction? How does the speed of the body change in this case?
3. What determines the maximum height of lift of a body thrown upward in the case when air resistance can be neglected?
4. What can be said about the signs of the projections of the vectors of the instantaneous velocity of the body and the acceleration of gravity during the free upward movement of this body?
5. How were the experiments depicted in Figure 30 carried out, and what conclusion follows from them?
1. What was called universal gravity?
2. What is another name for the forces of universal gravity?
3. Who discovered the law of universal gravitation and in what century?
4. How is the law of universal gravitation read?
5. Write down a formula expressing the law of universal gravitation.
6. In what cases should this formula be used to calculate gravitational forces?
7. Is the Earth attracted to an apple hanging on a branch?
1. Is it true? that the attraction of bodies towards the Earth is one of the examples of universal gravitation?
2. How does the force of gravity acting on a body change as it moves away from the Earth’s surface?
3. What formula can be used to calculate the force of gravity acting on a body if it is at a low altitude above the Earth?
4. In what case will the force of gravity acting on the same body be greater: if this body is located in the equatorial region of the globe or at one of the poles? Why?
5. What do you know about the acceleration of gravity on the Moon?
1. Look at Figure 33, a and answer the questions: under the influence of what force does the ball acquire speed and move from point B to point A? How did this force arise? What are the directions of the acceleration, the speed of the ball and the force acting on it? For what price
2. Consider Figure 33, b and answer the questions: why did the elastic force arise in the cord and how is it directed in relation to the cord itself? What can be said about the direction of the speed of the ball and the elastic force of the cord acting on it? How the ball moves:
3. Under what condition does a body move rectilinearly under the influence of a force, and under what condition does it move curvilinearly?
1. With the help of what experiment can you be convinced that the instantaneous speed of a body moving in a circle at any point of this circle is directed tangentially to it?
2. Where is the acceleration of a body directed when it moves in a circle with a constant velocity? What is this acceleration called?
3. What formula can be used to calculate the magnitude of the centripetal acceleration vector?
4. What is the direction of the force under the influence of which the body moves in a circle with a constant velocity?
1. Is it always possible to determine the position of a body at a given time t. knowing the initial position of this body (at t0 = 0) and the path traveled by it during the time interval t? Support your answer with examples.
2. What is called the movement of a body (material point)?
3. Is it possible to unambiguously determine the position of a body at a given moment of time t, knowing the initial position of this body (at t0 = 0) and the vector of movement made by the body during the period of time t? Support your answer with examples.
1. Give examples (from the field of astronomy) that prove that in the absence of resistance forces, a body can move indefinitely along a closed trajectory under the influence of a force that changes the direction of the speed of movement of this body.
2. Why do satellites, orbiting around the Earth under the influence of gravity, not fall to the Earth?
3. Can the revolution of a satellite around the Earth be considered a free fall?
4. What needs to be done with a physical body for it to become an artificial satellite of the Earth?
5. Derive a formula for calculating the first escape velocity of a satellite moving in a circular orbit near the Earth’s surface.
6. How does a satellite move at its first escape velocity? second escape velocity?
1. What is called the impulse of a body?
2. What can be said about the directions of the momentum vectors and the speed of a moving body?
3. What is taken as a unit of impulse?
4. How was the experiment depicted in Figure 42 carried out, and does it testify to it?
5. What does the statement mean? that several bodies form a closed system?
6. Formulate the law of conservation of momentum.
7. For a closed system consisting of two bodies, write the law of conservation of momentum in the form of an equation that would include the masses and velocities of these bodies. Explain what each symbol in this equation means.
1. Based on the law of conservation of momentum, explain why a balloon moves opposite to the stream of compressed air leaving it.
2. Give examples of the reactive motion of bodies.
3. What is the purpose of rockets?
4. Using Figure 45, list the main parts of any space rocket.
5. Describe the principle of operation of a rocket.
6. What does the speed of a rocket depend on?
7. What is the advantage of multi-stage rockets over single-stage ones?
8. How is a spacecraft landed?
1. What is called mechanical (total mechanical) energy?
2. How is the law of conservation of mechanical energy formulated?
3. Can the potential or kinetic energy of a closed system change over time?
1. What quantities are calculated with - vector or scalar?
2. Under what conditions will the projection of the vector onto the axis be positive, and under what conditions will it be negative?
3. Write down an equation that can be used to determine the coordinate of a body, knowing the coordinate of its initial position and the displacement vector.
1. What is called the speed of rectilinear uniform motion?
2. How to find the projection of the displacement vector of a body moving rectilinearly and uniformly if the projection of the velocity vector is known?
3. Under what condition is the magnitude of the displacement vector made by a body over a certain period of time equal to the path traveled by the body over the same period of time?
4. Prove that with uniform motion, the magnitude of the displacement vector is numerically equal to the area under the velocity graph.
5. What information about the motion of two bodies can be obtained from the graphs shown in Figure 7?
1. What type of motion - uniform or non-uniform - does rectilinear uniformly accelerated motion belong to?
2. What is meant by instantaneous speed of uneven motion?
3. What is called acceleration of uniformly accelerated motion?
4. What is uniformly accelerated motion?
5. What does the magnitude of the acceleration vector show?
6. What is the unit of acceleration?
7. Under what condition does the magnitude of the velocity vector of a moving body increase? is it decreasing?
1. Write down the formula by which you can calculate the projection of the instantaneous velocity vector of rectilinear uniformly accelerated motion if you know: a) the projection of the initial velocity vector and the projection of the acceleration vector; b) projection of the acceleration vector given that
2. What is the graph of the projection of the velocity vector of uniformly accelerated motion with an initial speed: a) equal to zero: b) not equal to zero?
3. How are the movements, the graphs of which are presented in Figures 11 and 12, similar and different from each other?
1. Using Figure 14, a. prove that the projection of the displacement vector during uniformly accelerated motion is numerically equal to the area of ​​the figure OASV.
2. Write down an equation to determine the projection of the displacement vector of a body during its rectilinear uniformly accelerated motion.
1. What formulas are used to calculate the projection and magnitude of the displacement vector of a body during its uniformly accelerated motion from a state of rest?
2. How many times will the module of the body’s displacement vector increase when the time of its movement from rest increases by n times?
3. Write down how the modules of the displacement vectors of a body moving uniformly accelerated from a state of rest relate to each other when the time of its movement increases by an integer number of times compared to t1.
4. Write down how the modules of the displacement vectors relate to each other, made by a body in successive equal intervals of time, if this body moves uniformly accelerated from a state of rest.
5. For what purpose can laws (3) and (4) be used?
1. What do the following statements mean: speed is relative. the trajectory of movement is relative, the path is relative?
2. Show with examples that speed, trajectory and distance traveled are relative quantities.
3. Briefly formulate what the relativity of motion is.
4. What is the main difference between the heliocentric system and the geocentric one?
5. Explain the change of day and night on Earth in the heliocentric system (see Fig. 18).
1. Can a car be considered a material point when determining the distance it travels in 2 hours, moving at an average speed of 80 km/h? when overtaking another car?
2. The plane flies from Moscow to Vladivostok. Can a controller observing its movement consider an airplane as a material point? passenger on this plane?
3. When talking about the speed of a car, train and other vehicles, the body of reference is usually not indicated. What is meant in this case by reference body?
4. The boy stood on the ground and watched his little sister ride on the carousel. After the ride, the girl told her brother that he, the houses, and the trees were quickly rushing past her. The boy began to claim that he, along with the houses and trees, was motionless
5. Relative to what reference body is motion considered when they say: a) the wind speed is 5 m/s; b) the log floats along the river, so its speed is zero; c) the speed of a tree floating along a river is equal to the speed of water flow in the river; d) any
On a table in a uniformly and rectilinearly moving train there is a lightly moving toy car. When the train braked, the car rolled forward without any external influence, maintaining its speed relative to the ground. Is the law of inertia fulfilled:
1. Determine the force under which a cyclist rolls down a hill with an acceleration equal to 0.8 m/s2, if the mass of the cyclist together with the bicycle is 50 kg.
2. 20 s after the start of movement, the electric locomotive reached a speed of 4 m/s. Find the force imparting acceleration if the mass of the electric locomotive is 184 tons.
3. Two bodies of equal mass move with accelerations of 0.08 m/s2 and 0.64 m/s2, respectively. Are the modules of the forces acting on the bodies equal? What is the force acting on the second body if a force of 1.2 N acts on the first?
4. With what acceleration will a ball with a mass of 0.5 kg floating under water float up if the force of gravity acting on it is 5 N, the Archimedean force is 10 N, and the average force of resistance to motion is 2 N?
5. A basketball, having passed through the hoop and the net, under the influence of gravity, first moves downwards with increasing speed, and after hitting the floor, upwards with decreasing speed. How are the vectors of acceleration, speed and movement of the ball directed in relation to
6. A body moves in a straight line with constant acceleration. What quantity characterizing the motion of this body is always co-directed with the resultant of forces applied to the body, and what quantities can be directed opposite to the resultant?
1. Figure 24 shows a stone lying on a board. Make the same drawing in your notebook and draw with arrows two forces that, according to Newton’s third law, are equal to each other. What are these forces? Label them.
2. Will the measurement limit of the dynamometer D shown in Figure 25 be exceeded if it is designed to measure forces up to 100 N inclusive?
3. Figure 26, a shows two carts connected to each other by a thread. Under the influence of a certain force F, the carts began to move with an acceleration a = 0.2 m/s2. a) Determine the projections onto the X axis of the forces F2 and F1 with which the thread acts, respectively, on the second
1. From what height did the icicle fall freely if it covered the distance to the ground in 4 s?
2. Determine the time it takes for a coin to fall if it is dropped from your hands at a height of 80 cm above the ground (g = 10 m/s2).
3. A small steel ball fell from a height of 45 m. How long did it take to fall? What displacement did the ball make during the first and last seconds of its movement? (g ≈ 10 m/s2.)
A tennis ball is thrown vertically upward with an initial speed of 9.8 m/s. After what period of time will the speed of the rising ball decrease to zero? How much movement will the ball make from the point of throw?
1. Give examples of the manifestation of gravity.
2. The space station flies from the Earth to the Moon. How does the modulus of the vector of its gravitational force towards the Earth change? to the moon? Is the station attracted to the Earth and the Moon with equal or different magnitude forces when it is in the middle between them? All three o
3. It is known that the mass of the Sun is 330,000 times greater than the mass of the Earth. Is it true that the Sun attracts the Earth 330,000 times stronger than the Earth attracts the Sun? Explain your answer.
4. The ball thrown by the boy moved upward for some time. At the same time, its speed decreased all the time until it became equal to zero. Then the ball began to fall down with increasing speed. Explain: a) did the force of attraction act on the ball?
5. Is a person standing on Earth attracted to the Moon? If so, what is it more attracted to: the Moon or the Earth? Is the Moon attracted to this person? Justify your answers.
1. What is the force of gravity acting on a body weighing 2.5 kg: 600 g; 1.2 t; 50 t? (g= 10 m/s2.)
2. Approximately determine the force of gravity acting on a person weighing 64 kg. (g ≈ 10 m/s2.) Is the globe attracted to this person? If so, what is this force approximately equal to?
3. The first Soviet artificial Earth satellite was launched on October 4, 1957. Determine the mass of this satellite if it is known that on Earth it was subject to a gravity force equal to 819.3 N.
4. Is it possible to calculate the force of gravity acting on a space rocket using the formula Fheavy = 9.8 m/s2 m, where m is the mass of the rocket, if this rocket flies at a distance of 5000 km from the Earth’s surface? (It is known that the radius of the Earth is approximately 6400 km.)
5. A hawk can hover at the same height above the Earth for some time. Does this mean that gravity does not act on it? What happens to a hawk if it folds its wings?
6*. A space rocket launches from Earth. At what distance from the Earth's surface will the rocket's gravity be 4 times less than before launch? 9 times less than before the start?
1. The ball rolled along the horizontal surface of the table from point A to point B (Fig. 35). At point B, the ball was acted upon by force F. As a result, it began to move towards point C. In which of the directions indicated by arrows 1, 2, 3 and 4 could force F act?
2. Figure 36 shows the trajectory of the ball. On it, circles mark the positions of the ball every second after the start of movement. Was there a force acting on the ball in the area 0-3; 4-6; 7-9: 10-12; 13-15; 16-19? If the force acted, then how would it
3*. In Figure 37, line ABCDE shows the trajectory of a certain body. In what areas did the force most likely act on the body? Could any force act on the body during its movement in other parts of this trajectory? Justify all answers.
1. When the washing machine is operating in drying mode, the surface of its drum, located at a distance of 21 cm from the axis of rotation, moves around this axis at a speed of 20 m/s. Determine the acceleration with which the points on the surface of the drum move.
2. Determine the acceleration of the end of the second hand of a clock if it is at a distance R = 2 cm from the center of rotation. (The length I of a circle of radius R is determined by the formula: I = 6.28R.)
3. Prove that the acceleration of the extreme point of the clock hand is twice as large as the acceleration of the middle point of this hand (i.e., the point located midway between the center of rotation of the hand and its end).
4. The minute and second hands of the clock rotate around a common center. The distances from the center of rotation to the ends of the arrows are the same. What is the ratio of the accelerations with which the ends of the arrows move? Which arrow moves with greater acceleration?
5. The mass of the Earth is 61024 kg, and the mass of the Moon is 71022 kg. Assuming that the Moon moves around the Earth in a circle with a radius of 384,000 km, determine: a) the force of attraction between the Earth and the Moon; b) centripetal acceleration with which the Moon moves around 3
1. Determine the speed of an artificial Earth satellite if it moves in a circular orbit at an altitude of 2600 km above the Earth’s surface. (MZ = 6 1024 kg; = 6.4 106 m; G = 6.67 10-11 N m2/kg2.)
2. If an artificial satellite were launched into a circular orbit near the surface of the Moon, it would move at a speed of 1.67 km/s. Determine the radius of the Moon if it is known that the acceleration of gravity on its surface is 1.6 m/s2.
1. What physical quantity is determined by the car driver using the speedometer counter - the distance traveled or the movement?
2. How should a car move over a certain period of time so that the module of movement made by the car during this period of time can be determined from its speedometer counter?
1. Two wind-up toy cars, each weighing 0.2 kg, move in a straight line towards each other. The speed of each car relative to the Earth is 0.1 m/s. Are the impulse vectors of the machines equal? impulse vector modules? Determine the projection of the impulse each
2. How much will the impulse of a car weighing 1 ton change (in absolute value) when its speed changes from 54 km/h to 72 km/h?
3. A man is sitting in a boat resting on the surface of a lake. At some point he gets up and walks from the stern to the bow. What will happen to the boat? Explain the phenomenon based on the law of conservation of momentum.
4. A railway car weighing 35 tons approaches a stationary car weighing 28 tons standing on the same track and automatically couples with it. After coupling, the cars move straight at a speed of 0.5 m/s. What was the speed of a car weighing 35 tons before the coupling?
1. From a boat moving at a speed of 2 m/s, a person throws an oar with a mass of 5 kg at a horizontal speed of 8 m/s opposite to the movement of the boat. At what speed did the boat begin to move after the throw, if its mass together with the mass of the person is 200 kg?
2. What speed will the rocket model get if the mass of its shell is 300 g, the mass of gunpowder in it is 100 g, and gases escape from the nozzle at a speed of 100 m/s? (Consider the gas outflow from the nozzle to be instantaneous.)
3. On what equipment and how is the experiment shown in Figure 47 carried out? What physical phenomenon is being demonstrated in this case, what does it consist of, and what physical law underlies this phenomenon? Note: The rubber tube was positioned
4. Perform the experiment shown in Figure 47. When the rubber tube deviates from the vertical as much as possible, stop pouring water into the funnel. While the water remaining in the tube flows out, observe how the following will change: a) the flight range of the water in the stream (relative to
1. Give a mathematical formulation of the law of conservation of mechanical energy (i.e. write it in the form of equations).
2. An icicle detached from the roof falls from a height h0 = 36 m from the ground. What speed v will it have at a height h = 31 m? (Imagine two solutions: with and without applying the law of conservation of mechanical energy; g = 10 m/s2.)
3. The ball flies out of a children's spring gun vertically upward with an initial speed v0 = 5 m/s. To what height will it rise from its departure point? (Imagine two solutions: with and without applying the law of conservation of mechanical energy; g = 10
1. A motorcyclist, having crossed a small bridge, moves along a straight section of the road. At a traffic light located 10 km from the bridge, a motorcyclist meets a cyclist. In 0.1 hour from the moment of meeting, the motorcyclist moves 6 km, and the bicycle
2. A boy holds a ball in his hands at a height of 1 m from the surface of the earth. Then he throws the ball vertically upward. Over a certain period of time t, the ball manages to rise 2.4 m from its initial position, reaching the point of greatest rise
1. Can the graph of the magnitude of the velocity vector be located under the Ot axis (i.e., in the region of negative values ​​of the velocity axis)? velocity vector projection graph?
2. Construct graphs of the projections of velocity vectors versus time for three cars moving rectilinearly and uniformly, if two of them are traveling in the same direction, and the third is moving towards them. The speed of the first car is 60 km/h, the second is 80 km/h
1. Over the same period of time, the magnitude of the velocity vector of the first car changed from v1 to v", and of the second - from v2 to v" (the speeds are shown on the same scale in Figure 9). Which car was moving at the indicated interval with the highest acceleration?
2. The plane, accelerating before takeoff, moved uniformly accelerated for a certain period of time. What was the acceleration of the plane if its speed increased from 10 to 55 m/s in 30 s?
3. With what acceleration did the train move on a certain section of the track if its speed increased by 6 m/s in 12 s?
1. A hockey player lightly hit the puck with his stick, giving it a speed of 2 m/s. What will be the speed of the puck 4 s after impact if, as a result of friction with ice, it moves with an acceleration of 0.25 m/s2?
2. A skier slides down a mountain from rest with an acceleration of 0.2 m/s2. After what period of time will its speed increase to 2m/s?
3. In the same coordinate axes, construct graphs of the projection of the velocity vector (on the X axis, co-directed with the initial velocity vector) for rectilinear uniformly accelerated motion for the cases: a) v0x = 1 m/s, ax = 0.5 m/s2; b) v0x = 1 m/s, ax = 1 m/s2; V
4. In the same coordinate axes, construct graphs of the projection of the velocity vector (on the X axis, codirectional with the initial velocity vector) for rectilinear uniformly accelerated motion for the cases: a) v0x = 4.5 m/s, ax = -1.5 m /s2; b) v0x = 3 m/s, ax = -1 m/
5. Figure 13 shows graphs of the dependence of the magnitude of the velocity vector on time during the rectilinear motion of two bodies. With what absolute acceleration does body I move? body II?
1. A cyclist rode down a hill in 5 s, moving with a constant acceleration of 0.5 m/s2. Determine the length of the slide if it is known that at the beginning of the descent the cyclist's speed was 18 km/h.
2. A train traveling at a speed of 15 m/s stopped 20 s after the start of braking. Assuming that the braking occurred with constant acceleration, determine the movement of the train in 20 s.
3. Reduce formula (1) from §7. If necessary, use the instructions in the answers.
1. A train leaving a station moves rectilinearly and uniformly accelerated during the first 20 s. It is known that in the third second from the start of movement the train traveled 2 m. Determine the magnitude of the displacement vector made by the train in the first second, and the magnitude of the vector
2. A car, moving uniformly accelerated from a state of rest, travels 6.3 m during the fifth second of acceleration. What speed did the car develop by the end of the fifth second from the start of movement?
1. Water in a river moves at a speed of 2 m/s relative to the shore. A raft is floating along the river. What is the speed of the raft relative to the shore? regarding the water in the river?
2. In some cases, the speed of a body may be the same in different reference systems. For example, a train moves at the same speed in the frame of reference associated with the station building and in the frame of reference associated with a tree growing by the road. Don't mind
3. Under what condition will the speed of a moving body be the same relative to two reference systems?
4. Thanks to the daily rotation of the Earth, a person sitting on a chair in his house in Moscow moves relative to the Earth’s axis at a speed of approximately 900 km/h. Compare this speed with the initial speed of the bullet relative to the gun, which is 250 m/s.
5*. The torpedo boat moves along the sixtieth parallel of southern latitude at a speed of 90 km/h relative to land. The speed of the Earth's daily rotation at this latitude is 223 m/s. What is the speed of the boat relative to the earth’s axis and where is it directed if
1. Give examples of oscillatory movements.
2. How do you understand the statement? that the oscillatory motion is periodic?
3. What is the period of oscillation?
4. What common feature (besides periodicity) do the movements of the bodies shown in Figure 48 have?
1. Look at Figure 49 and say whether the elastic force of the spring acts on the ball when it is at points B; WITH; ABOUT; D; A. Justify all answers.
2. Using Figure 49, explain why as the ball approaches point O from either side, its speed increases, and as it moves away from point O in any direction, the speed of the ball decreases.
3. Why doesn’t the ball stop when it reaches the equilibrium position?
4. What vibrations are called free?
5. What are called oscillatory systems?
6. What is called a pendulum?
7. How does a spring pendulum differ from a thread pendulum?
1. What is called the amplitude of oscillation; period of oscillation: frequency of oscillation? What letter is denoted and in what units is each of these quantities measured?
2. What is one complete oscillation?
3. What mathematical relationship exists between the period and frequency of oscillation?
4. How do: a) frequency depend? b) the period of free oscillations of the pendulum depending on the length of its thread?
5. What is called the natural frequency of an oscillatory system?
6. How are the velocities of two pendulums directed relative to each other at any moment of time if these pendulums oscillate in opposite phases? in the same phases?
1. Using Figure 59, tell us about the purpose, order of execution and results of the experiment depicted.
2. What is the name of the curved line shown in Figure 60? What do the segments OA and OT correspond to?
3. What oscillations are called harmonic?
4. What can be shown using the experiment depicted in Figure 61?
5. What is called a mathematical pendulum?
6. Under what conditions will a real string pendulum oscillate close to harmonic?
7. How do the force acting on a body, its acceleration and speed change when it performs harmonic oscillations?
1. How do the speed and kinetic energy of the pendulum (see Fig. 49) change as the ball approaches the equilibrium position? Why?
2. What can be said about the total mechanical energy of an oscillating pendulum at any moment in time, assuming that there is no energy loss? According to what law can this be stated?
3. Can a body, being in real conditions, perform oscillatory motion without loss of energy?
4. How does the amplitude of damped oscillations change over time?
5. Where will the pendulum stop oscillating faster: in the air or in the water? (The initial energy reserve is the same in both cases.)
1. Can free oscillations be undamped? Why?
2. What needs to be done to ensure that the oscillations are undamped?
3. What oscillations are called forced?
4. What is driving force?
5. In what case do they say that the oscillations are established?
6. What can be said about the frequency of steady-state forced oscillations and the frequency of the driving force?
7. Can bodies that are not oscillatory systems perform forced oscillations? Give examples.
8. How long do forced oscillations occur?
1. For what purpose and how was the experiment carried out with two pendulums shown in Figure 64, a?
2. What is the phenomenon called resonance?
3. Which of the pendulums shown in the figure. 64, b. oscillates in resonance with pendulum 3? By what signs did you determine this?
4. To what oscillations - free or forced - is the concept of resonance applicable?
5. Give examples showing that in some cases resonance can be a beneficial phenomenon, and in others it can be harmful.
1. What are called waves?
2. What is the main general property of traveling waves of any nature?
3. Does matter transfer occur in a traveling wave?
4. What are elastic waves?
5. Give examples of types of waves that are not elastic.
1. What waves are called longitudinal? transverse? Give examples.
2. Which waves - transverse or longitudinal - are shear waves? waves of compression and rarefaction?
3. In what medium can elastic transverse waves propagate? elastic longitudinal waves?
4. Why do elastic transverse waves not propagate in liquid and gaseous media?
1. What is wavelength called?
2. What letter indicates wavelength?
3. How long does it take for the oscillatory process to spread over a distance equal to the wavelength?
4. What formulas can be used to calculate the wavelength and speed of propagation of transverse and longitudinal waves?
5. The distance between which points is equal to the length of the longitudinal wave shown in Figure 69?
1. Tell us about the experiments depicted in Figures 70 - 73. What conclusion follows from them?
2. What common property do all sound sources have?
3. Mechanical vibrations of what frequencies are called sound vibrations and why?
4. What vibrations are called ultrasonic? infrasonic?
5. Tell us about measuring the depth of the sea using echolocation.
1. Based on Figure 70, tell us how the dependence of the pitch of sound on the frequency of vibration of its source was studied. What was the conclusion?
2. What was the purpose of the experiment depicted in Figure 75? Describe how this experiment was carried out and what conclusion was reached.
3. How to verify experimentally that of two tuning forks the higher sound is produced by the one. Which one has a higher natural frequency? (The frequencies on the tuning forks are not indicated.)
4. What does the pitch of sound depend on?
5. What is a pure tone?
6. What are the fundamental tone and overtones of sound?
7. What determines the pitch of sound?
8. What is the timbre of sound and how is it determined?
1. What is the purpose of the experiment depicted in Figure 72, and how is it carried out?
2. How will the volume of the sound change if the amplitude of the vibrations of its source is reduced?
3. What frequency sound - 500 Hz or 3000 Hz - will the human ear perceive as louder given the same vibration amplitudes of the sources of these sounds?
4. What determines the volume of sound?
5. Name the units of volume and sound level.
6. How does the systematic effect of loud sounds affect human health?
1. What is the purpose of the experiment depicted in Figure 77? Describe how this experiment is carried out and what conclusion follows from it.
2. Can sound travel in gases, liquids, and solids? Support your answers with examples.
3. Which bodies conduct sound better - elastic or porous? Give examples of elastic and porous bodies.
4. How to ensure soundproofing of premises. those. protect premises from extraneous sounds?
1. At what frequency does the eardrum of a person’s ear vibrate when sound reaches it?
2. What wave - longitudinal or transverse - is sound propagating in the air? in the water?
3. Give an example showing that a sound wave does not travel instantly, but at a certain speed.
4. What is the speed of sound propagation in air at 20 °C?
5, 6. Does the speed of sound depend on the medium in which it travels? What is the speed of sound in air?
1. What causes an echo?
2. Why does an echo not occur in a small room filled with furniture, but in a large, half-empty room?
3. How can the sound properties of a large hall be improved?
4. Why does sound travel a greater distance when using a horn?
1. Give examples of the manifestation of sound resonance that are not mentioned in the text of the paragraph.
2. Why are tuning forks installed on resonator boxes?
3. What is the purpose of resonators used in musical instruments?
4. What does the timbre of sound depend on?
5. What is the source of a person's voice?
1. Using Figures 82 - 84, briefly describe how the experiment on the addition of sound waves was carried out.
2. What is the difference between the paths of two waves?
3. What pattern was revealed as a result of the experiment depicted in Figures 82-84?
4. What waves are called coherent?
5. What is an interference pattern and from what sources can it be obtained?
6. What phenomenon is called interference?
7. How can you verify by ear that an interference pattern is being formed?
8. What types of waves are characterized by the phenomenon of interference?
1. Which of the listed systems are oscillatory?
2
1. Figure 58 shows pairs of oscillating pendulums. In what cases do two pendulums oscillate: in the same phases relative to each other? in opposite phases?
2. The vibration frequency of a hundred-meter railway bridge is 2 Hz. Determine the period of these oscillations.
3. The period of vertical oscillations of a railway car is 0.5 s. Determine the vibration frequency of the car.
4. The sewing machine needle makes 600 complete vibrations in one minute. What is the frequency of vibration of the needle, expressed in hertz?
5. The amplitude of oscillation of the load on the spring is 3 cm. How far from the equilibrium position will the load travel in ¼ T; ½T; ¾T; T.
6. The amplitude of oscillation of the load on the spring is 10 cm, frequency 0.5 Hz. How far will the load travel in 2 s?
7. The horizontal spring pendulum shown in Figure 49 oscillates freely. What quantities characterizing this movement (amplitude, frequency, period, speed, force under the influence of which oscillations occur) are constant, and
1. The horizontal spring pendulum shown in Figure 49 was moved to the side and released. How do the quantities listed in the table, which characterize the oscillatory motion of this pendulum, change along the indicated sections of its path? Redraw table 1 into those
2. Figure 63 shows a ball on a string oscillating without friction between points A and B. Being at point B, this pendulum has a potential energy equal to 0.01 J relative to horizontal 1, taken as the zero level of potential energy.
1. Look at Figure 52 and say which bodies are capable of performing: free vibrations; forced vibrations. Justify your answer.
2. Can: a) forced oscillations occur in an oscillatory system; b) free oscillations in a system that is not oscillatory? Give examples.
1. Pendulum 3 (see Fig. 64, b) performs free oscillations, a) What oscillations - free or forced - will pendulums 1, 2 and 4 perform? b) What causes the driving force acting on pendulums 1, 2 and 4? c) What are the proper
2. The water that the boy is carrying in the bucket begins to splash heavily. The boy changes the pace of his walk (or simply “kicks his foot”), and the splashing stops. Why is this happening?
3. The natural frequency of the swing is 0.6 Hz. At what intervals should you push them in order to swing them as much as possible using a relatively small force?
1. At what speed does a wave propagate in the ocean if the wavelength is 270 m and the oscillation period is 13.5 s?
2. Determine the wavelength at a frequency of 200 Hz if the wave speed is 340 m/s.
3. A boat rocks on waves traveling at a speed of 1.5 m/s. The distance between the two nearest wave crests is 6 m. Determine the period of oscillation of the boat.
We hear the sound of the flapping wings of a flying mosquito, but we do not hear the sound of a flying bird. Why?
1. Which insect flaps its wings more often in flight - a bumblebee, a mosquito or a fly? Why do you think so?
2. The teeth of a rotating circular saw create a sound wave in the air. How will the pitch of the sound produced by the saw change when it is idling if it starts sawing a thick board of dense wood? Why?
3. It is known that the tighter a guitar string is, the higher the sound it produces. How will the pitch of guitar strings change if the ambient temperature increases significantly? Explain your answer.
1. Can the sound of a large explosion on the Moon be heard on Earth? Justify your answer.
2. If you tie one half of a soap dish to each end of the thread, then with the help of such a telephone you can talk even in a whisper, being in different rooms. Explain the phenomenon.
1. Determine the speed of sound in water if a source oscillating with a period of 0.002 s excites waves in water with a length of 2.9 m.
2. Determine the wavelength of a sound wave with a frequency of 725 Hz in air, in water and in glass.
3. One end of a long metal pipe was struck once with a hammer. Will the sound from the impact travel to the other end of the pipe through the metal? through the air inside the pipe? How many blows will a person standing at the other end of the pipe hear?
4. An observer standing near a straight section of the railway saw steam above the whistle of a steam locomotive going in the distance. 2 s after the appearance of steam, he heard the sound of a whistle, and after 34 s the locomotive passed by the observer. Determine the speed of movement of the steam
5*. The observer moves away from the bell, which is struck every second. At first, the visible and audible impacts coincide. Then they stop matching. Then, at some observer's distance from the bell, the visible and audible strikes coincide again. Explain it
1. What generates a magnetic field?
2. What creates the magnetic field of a permanent magnet?
3. What are magnetic lines?
4. How are magnetic needles located in a magnetic field whose lines are straight? curvilinear?
5. What is taken to be the direction of the magnetic line at any point?
6. How can you use magnetic lines to show that in one region of space the field is stronger than in another?
7. What can be judged from the pattern of magnetic field lines?
1. What do you know about the direction and shape of the field lines of a bar magnet?
2. What kind of magnetic field—uniform or inhomogeneous—is formed around a strip magnet? around a straight conductor carrying current? inside a solenoid whose length is significantly greater than its diameter?
3. What can be said about the magnitude and direction of the force acting on the magnetic needle at different points of the inhomogeneous magnetic field? uniform magnetic field?
4. Compare the patterns of line locations in inhomogeneous and homogeneous magnetic fields.
5. How are magnetic field lines directed perpendicular to the drawing plane depicted?
1. How can you experimentally show the connection between the direction of the current in a conductor and the direction of its magnetic field line?
2. Formulate the gimlet rule.
3. What can be determined using the gimlet rule?
4. State the right hand rule for the solenoid.
5. What can be determined using the right hand rule?
1. How can we experimentally detect the presence of a force acting on a current-carrying conductor in a magnetic field?
2. How is a magnetic field detected?
3. What determines the direction of the force acting on a current-carrying conductor in a magnetic field?
4. How is the left-hand rule read for a current-carrying conductor in a magnetic field? for a charged particle moving in this field?
5. What is taken to be the direction of the current in the external part of the electrical circuit?
6. What can you determine using the left-hand rule?
7. In what case is the force of a magnetic field on a current-carrying conductor or a moving charged particle equal to zero?
1. What is the name and symbol for the vector quantity that serves as a quantitative characteristic of the magnetic field?
2. What formula is used to determine the magnitude of the magnetic induction vector of a uniform magnetic field?
3. What is taken as a unit of magnetic induction? What is this unit called?
4. What are magnetic induction lines called?
5. In which case is the magnetic field called uniform, and in which case is it called inhomogeneous?
6. How does the force acting at a given point in the magnetic field on a magnetic needle or a moving charge depend on the magnetic induction at this point?
1. What determines the magnetic flux that penetrates the area of ​​a flat circuit placed in a uniform magnetic field?
2. How does the magnetic flux change when the magnetic induction increases n times, if neither the area nor the orientation of the circuit changes?
3. At what orientation of the circuit relative to the lines of magnetic induction is the magnetic flux penetrating the area of ​​this circuit maximum? equal to zero?
4. Does the magnetic flux change with such a rotation of the circuit, when the lines of magnetic induction then penetrate it. then they slide along its plane?
1. What was the purpose of the experiments depicted in Figures 126-128? How were they carried out?
2. Under what condition did an induced current arise in all experiments in a coil closed to a galvanometer?
3. What is the phenomenon of electromagnetic induction?
4. What is the importance of the discovery of the phenomenon of electromagnetic induction?
1. Why was the experiment depicted in Figures 130 and 133 carried out?
2. Why does the split ring not respond to the approach of a magnet?
3. Explain the phenomena that occur when a magnet approaches a solid ring (see Fig. 132); when removing the magnet (see Fig. 134).
4. How did we determine the direction of the induction current in the ring?
5. Formulate Lenz’s rule.
1. What phenomenon was studied in the experiments presented in Figures 135 and 136?
2. Tell us first about the first and then about the second part of the experiment: what you did, what you saw, how the observed phenomena are explained.
3. What is the phenomenon of self-induction?
4. Can a self-induction current occur in a straight conductor carrying current? If not, explain why; if yes. then under what condition.
5. By reducing what energy was the work done to create an induction current when the circuit was opened?
1. What electric current is called alternating? With the help of what simple experience can it be obtained?
2. Where is alternating electric current used?
3. On what phenomenon is the operation of the currently most common alternating current generators based?
4. Tell us about the structure and operating principle of an industrial generator.
5. What drives the generator rotor at a thermal power plant? at a hydroelectric power station?
6. Why are multi-pole rotors used in hydrogen generators?
7. What is the standard frequency of industrial current used in Russia and many other countries?
8. By what physical law can energy losses in power lines be determined?
9. What should be done to reduce electricity losses during transmission?
10. Why, when the current strength decreases, is its voltage increased by the same amount before being fed into the power line?
11. Tell us about the structure, principle of operation and application of transformers.
1. Who and when was the theory of the electromagnetic field created and what was its essence?
2. What is the source of the electromagnetic field?
3. How do the vortex electric field lines differ from the electrostatic field lines?
4. Describe the mechanism of occurrence of induced current, based on knowledge of the existence of an electromagnetic field.
1. What conclusions regarding electromagnetic waves followed from Maxwell’s theory?
2. What physical quantities change periodically in an electromagnetic wave?
3. What relationships between the wavelength, its speed, period and frequency of oscillations are valid for electromagnetic waves?
4. Under what condition will the wave be intense enough to be detected?
5. When and by whom were electromagnetic waves first received?
6. Give examples of 2-3 ranges of electromagnetic waves.
7. Give examples of the use of electromagnetic waves and their effects on living organisms.
1. What is the purpose of the capacitor?
2. What is the simplest capacitor? How is it indicated on the diagrams?
3. What is meant by capacitor charge?
4. What and how does the capacitance of the capacitor depend?
5. What formula is used to determine the energy of a charged capacitor?
6. How was the experiment depicted in Figure 149 carried out? What does he prove?
7. Explain the structure and operation of a variable capacitor. Where is it most widely used?
1. Why are electromagnetic waves supplied to the antenna?
2. Why are high frequency electromagnetic waves used in radio broadcasting?
3. What kind of system is an oscillatory circuit and what devices does it consist of?
4. Tell us about the purpose, progress and observed result of the experiment depicted in Figure 152?
5. What energy transformations occur as a result of electromagnetic oscillations?
6. Why does the current in the coil not stop when the capacitor is discharged?
7. How could a galvanometer, not included in the oscillatory circuit, register the oscillations occurring in this circuit?
8. What does the intrinsic period of an oscillatory circuit depend on? How can it be changed?
1. What is called radio communication?
2. Give 2-3 examples of the use of radio communication lines.
3. Using Figures 154 and 155, tell us about the principles of radiotelephone communication.
4. What frequency of oscillations is called carrier?
5. What is the process of amplitude modulation of electrical vibrations?
6. Why are electromagnetic waves of sound frequencies not used in radio communications?
7. What is the process of vibration detection?
1. What two views on the nature of light have existed for a long time among scientists?
2. What was the essence of Jung’s experiment, what did this experiment prove and when was it carried out?
3. How was the experiment depicted in Figure 156, a, carried out?
4. Using Figure 156, b, explain why alternating stripes appear on the soap film.
5. What does the experiment shown in Figure 156 prove?
6. What can you say about the frequency (or wavelength) of light waves of different colors?
1. What waves did scientists imagine light in at the beginning of the 19th century?
2. What caused the need to put forward a hypothesis about the existence of luminiferous ether?
3. What assumption about the nature of light was made by Maxwell? What general properties of light and electromagnetic waves were the basis for this assumption?
4. What is the name of a particle of electromagnetic radiation?
1. Define relative and absolute refractive index.
2. What is the absolute refractive index of vacuum?
3. For which refractive index values ​​- relative or absolute - are there tables?
4. Which of the two substances is called optically denser?
5. How are refractive indices determined through the speed of light in media?
6. Where does light travel at the fastest speed?
7. What is the physical reason for the decrease in the speed of light when it passes from a vacuum to a medium or from a medium with a lower optical density to a medium with a higher one?
8. What determines (i.e., what does it depend on) the absolute refractive index of a medium and the speed of light in it?
9. Tell what is shown in figure 160 and what this figure illustrates.
1. What was the purpose of the experiment depicted in Figure 161, and how was it carried out? What is the result of the experiment and what conclusion follows from it?
2. What is the dispersion of light?
3. Tell us about the experiment on the refraction of white light in a prism. (Progress of experiment, results, conclusion.)
4. What kind of light is called simple? What is another name for the light of simple colors?
5. What did we verify by using a lens to collect light from all colors of the spectrum into white?
6. Tell us about the experience depicted in Figure III of the color insert.
7. What is the physical reason for the difference in the colors of the bodies around us?
1. Using Figure 163, tell us about the structure of the spectrograph.
2. What type of spectrum is obtained using a spectroscope if the light studied in it is a mixture of several simple colors?
3. What is a spectrogram?
4. How does a spectrograph differ from a spectroscope?
1. What does a continuous spectrum look like?
2. The light of which bodies produces a continuous spectrum? Give examples.
3. What do line spectra look like?
4. How can a line emission spectrum of sodium be obtained?
5. What light sources produce line spectra?
6. What is the mechanism for obtaining line absorption spectra (i.e., what needs to be done to obtain them)?
7. How to obtain a line absorption spectrum of sodium and what does it look like?
8. What is the essence of Kirchhoff’s law regarding line emission and absorption spectra?
1. What is spectral analysis?
2. How is spectral analysis carried out?
3. How can we determine from the photographs of the test sample obtained in the experiment which chemical elements are included in its composition?
4. Is it possible to determine the amount of each of its chemical elements from the spectrum of a sample?
5. Explain the application of spectral analysis.
1. Formulate Bohr’s postulates.
2. Write down equations to determine the energy and frequency of the emitted photon.
3. What state of the atom is called the ground state? excited?
4. How is the coincidence of lines in the emission and absorption spectra of a given chemical element explained?
1. Figure 88 shows a section BC of a conductor carrying current. Around it in one of the planes are shown the lines of the magnetic field created by this current. Is there a magnetic field at point A?
2. Figure 88 shows three points: A, M, N. At which of them will the magnetic field of the current flowing through the conductor BC act on the magnetic needle with the greatest force? with the least force?
1. Figure 94 shows a wire coil with current and the lines of the magnetic field created by this current. a) Are there any points A, B, C and D indicated in the figure at which the field would act on the magnetic needle with the same magnitude force? (AC = AD,
2. Consider Figure 94 and determine whether it is possible in a non-uniform magnetic field created by a coil with current to find points at which the force of the field on the magnetic needle would be the same both in magnitude and in direction. If yes, then do it in those
1. Figure 99 shows a wire rectangle, the direction of the current in it is shown by arrows. Redraw the drawing in a notebook and, using the gimlet rule, draw one magnetic line around each of its four sides, indicating its direction with an arrow.
2. Figure 100 shows the magnetic field lines around current-carrying conductors. Conductors are depicted as circles. Draw the drawing in a notebook and use symbols to indicate the directions of currents in the conductors, using the gimlet rule for this.
3. A current of the indicated direction is passed through a coil, inside of which there is a steel rod (Fig. 101). Determine the poles of the resulting electromagnet. How can you change the position of the poles of this electromagnet?
4. Determine the direction of the current in the coil and the poles at the current source (Fig. 102), if, when current passes through the coil, the magnetic poles indicated in the figure appear.
5. The direction of the current in the turns of the winding of a horseshoe-shaped electromagnet is shown by arrows (Fig. 103). Identify the poles of an electromagnet.
6. Parallel wires carrying currents in the same direction attract, and parallel beams of electrons moving in the same direction repel. In which of these cases is the interaction due to electrical forces, and in which is it due to magnetic forces?
1. In which direction will the light aluminum tube roll when the circuit is closed (Fig. 112)?
2. Figure 113 shows two bare conductors connected to a current source and a light aluminum tube AB. The entire installation is located in a magnetic field. Determine the direction of the current in the tube AB if, as a result of the interaction of this current with the magnet
3. Between the poles of the magnets (Fig. 114) there are four current-carrying conductors. Determine which direction each of them is moving.
4. Figure 115 shows a negatively charged particle. moving with speed v in a magnetic field. Make the same drawing in your notebook and indicate with an arrow the direction of the force with which the field acts on the particle.
5. A magnetic field acts with a force F on a particle moving with speed v (Fig. 116). Determine the sign of the particle's charge.
1. A straight conductor was placed in a uniform magnetic field perpendicular to the lines of magnetic induction, through which a current of 4 A flows. Determine the induction of this field if it acts with a force of 0.2 N for every 10 cm of the length of the conductor.
2. A conductor with current was placed in a magnetic field with induction B. After some time, the current in the conductor was reduced by 2 times. Did the induction B of the magnetic field in which the conductor was placed change? Was the decrease in current accompanied by changes in
A wire coil K with a steel core is connected to a DC source circuit in series with a rheostat R and a switch K (Fig. 125). The electric current flowing through the turns of coil K1 creates a magnetic field in the space around it. In the field
1. How to create a short-term induction current in the K2 coil shown in Figure 125?
2. The wire ring is placed in a uniform magnetic field (Fig. 129). The arrows shown next to the ring show that in cases a and b the ring moves rectilinearly along the lines of magnetic field induction, and in cases c, d and e it rotates around the axis
1. Why do you think the device shown in Figure 130 is made of aluminum? How would the experiment proceed if the device were made of iron? copper?
2. In the list of logical operations given below that we performed to determine the direction of the induction current, the sequence of their implementation is broken. Write down the letters representing these operations in your notebook, arranging them in the correct sequence.
In the electrical circuit (Fig. 137), the voltage received from the current source is less than the ignition voltage of the neon lamp. What will happen to each element of the circuit (excluding the current source and the key) when the key is closed? when the key is closed? when opening?
1. Russian power plants produce alternating current with a frequency of 50 Hz. Determine the period of this current.
2. Using the graph (see Fig. 140), determine the period, frequency and amplitude of fluctuations in current i.
In the experiment depicted in Figure 127, when the key is closed, the current flowing through coil A increased for a certain period of time. At the same time, a short-term current arose in the circuit of coil C. Are electric fields different in any way?
1. At what frequency do ships transmit the SOS distress signal if, according to international agreement, the radio wave length should be 600 m?
2. A radio signal sent from the Earth to the Moon can reflect off the surface of the Moon and return to Earth. Suggest a way to measure the distance between the Earth and the Moon using a radio signal.
3. Is it possible to measure the distance between the Earth and the Moon using a sound or ultrasonic wave? Justify your answer.
1. During what period of time did each radio signal of the radiogram transmitted by A. S. Popov reach the receiving device?
2. A capacitor with a capacity of 1 μF is charged to a voltage of 100 V. Determine the charge of the capacitor.
3. How will the capacitance of a flat-plate capacitor change when the distance between the plates is reduced by 2 times?
4. Prove that the field energy Eel of a flat capacitor can be determined by the formula Eel = CU2/2.
5. Three capacitors are connected in parallel. The capacity of one of them is 15 μF, the other is 10 μF, and the third is 25 μF. Determine the capacitance of the capacitor bank.
The oscillating circuit consists of a variable capacitor and a coil. How to obtain electromagnetic oscillations in this circuit, the periods of which would differ by a factor of 2?
The period of oscillation of charges in an antenna emitting radio waves is 10-7 s. Determine the frequency of these radio waves.
1. Which of the three quantities - wavelength, frequency and speed of wave propagation - will change when the wave passes from vacuum to diamond?
2. Using equations (6) and (7), prove that n21= n2/n1, where
is the absolute refractive index of the first medium, and n2 is the second.
Hint: express from equation (7) the speed v of light in the medium in terms of c and n; by analogy with the formula obtained, write down the formulas for determining the velocities v1 and v2 included in equation (6); replace v1 and v2 in equation (6) with their corresponding letter expressions
1. On a table in a dark room there are two sheets of paper - white and black. There is an orange circle pasted in the center of each sheet. What will we see if we illuminate these sheets with white light? orange light of the same shade as the circle?
2. Write on a white sheet of paper the first letters of the names of all the colors of the spectrum with felt-tip pens of the corresponding colors: K - red, O - orange, F - yellow, etc. Examine the letters through a three-centimeter layer of brightly colored transparent liquid poured into the t
3. Why is the color of the same body slightly different in daylight and evening light?
Consider Figure 164, c and explain why, when entering the ADB prism, the rays are deflected towards its wider part (the angle of refraction is less than the angle of incidence), and when entering the DBE prism - towards its narrower part (the angle of refraction is greater than the angle of incidence
1. What was the discovery made by Becquerel in 1896?
2. What did they call the ability of atoms of some chemical elements to spontaneously emit?
3. Tell us how the experiment was carried out, the diagram of which is shown in Figures 167, a, b. What emerged from this experience?
4. What were the names of the particles that make up radioactive radiation? What are these particles?
5. What did the phenomenon of radioactivity indicate?
1. What was an atom according to the model proposed by Thomson?
2. Using Figure 168, tell how the experiment on the scattering of α-particles was carried out.
3. What conclusion was made by Rutherford based on this. that some α-particles, when interacting with the foil, were scattered at large angles?
4. What is an atom according to the nuclear model. put forward by Rutherford?
5. Based on Figure 169, tell how alpha particles pass through atoms of matter according to the nuclear model.
1. What happens to radium as a result of α decay?
2. What happens to radioactive chemical elements as a result of α- or β-decay?
3. Which part of the atom - the nucleus or the electron shell - undergoes changes during radioactive decay? Why do you think so?
4. Write down the α-decay reaction of radium and explain what each symbol in this notation means.
5. What are the names of the upper and lower numbers that appear before the letter designation of the element?
6. What is the mass number? charge number?
7. Using the example of the a-decay reaction of radium, explain what the laws of conservation of charge (charge number) and mass number are.
8. What conclusion followed from the discovery made by Rutherford and Soddy?
9. What is radioactivity?
1. Based on Figure 170, tell us about the structure and principle of operation of the Geiger counter.
2. To register what particles is a Geiger counter used?
3. Based on Figure 171, tell us about the structure and principle of operation of a cloud chamber.
4. What characteristics of particles can be determined using a cloud chamber placed in a magnetic field?
5. What is the advantage of a bubble chamber over a cloud chamber? How are these devices different?
1. Tell about the experiment conducted by Rutherford in 1919.
2. What does the photograph of particle tracks in a cloud chamber indicate (Fig. 172)?
3. What is the other name and symbol for the nucleus of a hydrogen atom? What is its mass and charge?
4. What assumption (regarding the composition of nuclei) did the results of experiments on the interaction of α-particles with the nuclei of atoms of various elements allow one to make?
1. What contradiction does the assumption lead to? that the nuclei of atoms consist only of protons? Explain this with an example.
2. Who first suggested the existence of an electrically neutral particle with a mass approximately equal to the mass of a proton?
3. Who and when was the first to prove that beryllium radiation is a flux of neutrons?
4. How was it proven that neutrons have no electric charge? How was their mass estimated?
5. How is a neutron designated, what is its mass compared to the mass of a proton?
1. What are protons and neutrons together called?
2. What is called a mass number and what letter is it denoted by?
3. What can be said about the numerical value of the mass of an atom (in amu) and its mass number?
4. What is the name and letter for the number of protons in the nucleus?
5. What can be said about the charge number, the charge of the nucleus (expressed in elementary electric charges) and the serial number in D.I. Mendeleev’s table for any chemical element?
6. How is it generally accepted to designate the nucleus of any chemical element?
7. What letter denotes the number of neutrons in a nucleus?
8. What formula relates the mass number, charge number and number of neutrons in the nucleus?
9. How can the existence of nuclei with identical charges and different masses be explained from the point of view of the proton-neutron model of the nucleus?
1. What question arose in connection with the hypothesis that the nuclei of atoms consist of protons and neutrons? What assumption did scientists have to make to answer this question?
2. What are the forces of attraction between nucleons in a nucleus called and what are their characteristic features?
1. What is the binding energy of a nucleus?
2. Write down the formula for determining the mass defect of any nucleus.
3. Write down a formula for calculating the binding energy of a nucleus from its mass defect.
1. When was the fission of uranium nuclei when bombarded with neutrons discovered?
2. Why can nuclear fission begin only when it is deformed under the influence of a neutron absorbed by it?
3. What is formed as a result of nuclear fission?
4. What energy does part of the internal energy of the nucleus transform into when it divides?
5. What type of energy is converted into the kinetic energy of fragments of a uranium nucleus when they are decelerated in the environment?
6. How does the fission reaction of uranium nuclei proceed - with the release of energy into the environment or, conversely, with the absorption of energy?
1. Explain the mechanism of a chain reaction using Figure 174.
2. What is the critical mass of uranium?
3. Is it possible for a chain reaction to occur if the mass of uranium is less than the critical mass? Why?
4. How does a chain reaction occur in uranium if its mass is greater than the critical mass? Why?
5. Due to what factors can the number of free neutrons in a piece of uranium be increased, thereby ensuring the possibility of a chain reaction occurring in it?
1. What is a nuclear reactor?
2. What is the control of a nuclear reaction?
3. Name the main parts of the reactor.
4. What is in the core?
5. Why is it necessary that the mass of each uranium rod be less than the critical mass?
6. What are control rods used for? How are they used?
7. What second function (besides moderating neutrons) does water perform in the primary circuit of the reactor?
8. What processes occur in the second circuit?
9. What energy transformations occur when generating electric current at nuclear power plants?
1. In connection with this, in the middle of the 20th century. Is there a need to find new energy sources?
2. Name two main advantages of nuclear power plants over thermal power plants. Justify your answer.
3. Name three fundamental problems of modern nuclear energy.
4. Give examples of ways to solve problems in nuclear energy.
1. What is the reason for the negative effects of radiation on living beings?
2. What is the absorbed dose of radiation? By what formula is it determined and in what units is it measured?
3. Does radiation cause more harm to the body at a higher or lower dose if all other conditions are the same?
4. Do different types of ionizing radiation cause the same or different biological effects in a living organism? Give examples.
5. What does the radiation quality factor show? What is it equal to for α-, β-, γ- and X-ray radiation?
6. In connection with what and why was the value called the equivalent radiation dose introduced? By what formula is it determined and in what units is it measured?
7. What other factor (besides energy, type of radiation and body weight) should be taken into account when assessing the effects of ionizing radiation on a living organism?
8. What percentage of atoms of a radioactive substance will remain after 6 days if its half-life is 2 days?
9. Tell us about methods of protection from exposure to radioactive particles and radiation.
1. What reaction is called thermonuclear?
2. Why are thermonuclear reactions possible only at very high temperatures?
3. Which reaction is energetically more favorable (per nucleon): the synthesis of light nuclei or the fission of heavy ones?
4. Give an example of a thermonuclear reaction.
5. What is one of the main difficulties in carrying out thermonuclear reactions?
6. What is the role of thermonuclear reactions in the existence of life on Earth?
7. What hypotheses about the sources of solar energy do you know?
8. What is the source of solar energy according to modern ideas?
9. How long should the supply of hydrogen on the Sun last, according to scientists’ calculations?
1. Determine the mass (in amu accurate to whole numbers) and charge (in elementary charges) of the atomic nuclei of the following elements: carbon 126C; lithium 63Li; calcium 4020Ca.
2. How many electrons are contained in the atoms of each of the chemical elements listed in the previous problem?
3. Determine (to within whole numbers) how many times the mass of the nucleus of the lithium atom 63Li is greater than the mass of the nucleus of the hydrogen atom 11H.
4. For the nucleus of the beryllium atom 94Be, determine: a) mass number; b) the mass of the nucleus in a. e.m. (accurate to integers); c) how many times is the mass of the nucleus greater than 1/12 the mass of the 126C carbon atom (accurate to whole numbers): d) charge number; e) nuclear charge in the element
5. Using the laws of conservation of mass number and charge, determine the mass number and charge of the nucleus of the chemical element X formed as a result of the following β-decay reaction: 146C → X + 0-1e, where 0-1e is a β-particle (electron). Find this one
Consider the recording of the nuclear reaction of the interaction of nitrogen and helium nuclei, resulting in the formation of oxygen and hydrogen nuclei. Compare the total charge of the interacting nuclei with the total charge of the nuclei formed as a result of this interaction. Do it
1. How many nucleons are in the nucleus of the beryllium atom 94Be? How many protons does it have? neutrons?
2. For the potassium atom 3919K, determine: a) charge number; b) number of protons; c) nuclear charge (in elementary electric charges); d) number of electrons; e) serial number in D.I. Mendeleev’s table; f) mass number of the nucleus; g) number of nucleons; a) the number of nate
3. Using the table of D.I. Mendeleev, determine which atom of a chemical element has: a) 3 protons in the nucleus; b) 9 electrons.
4. During α-decay, the original nucleus, emitting an α-particle 42He, transforms into the nucleus of an atom of another chemical element. For example, How many cells and in which direction (to the beginning or to the end of D.I. Mendeleev’s table) is the resulting element displaced but relative
5. During the β-decay of the original nucleus, one of the neutrons entering this nucleus turns into a proton, an electron 0-1e and an antineutrino 00v (a particle that easily passes through the globe and, possibly, has no mass). The electron and antineutrino fly out from the nucleus, and about
Do you think there are gravitational attraction forces (i.e., universal gravity forces) between the nucleons in the nucleus?
1. For each of the vectors shown in Figure 191, determine: a) the coordinates of the beginning and end; b) projections onto the y-axis; c) modules of projections onto the y-axis, d) modules of vectors.
2. In Figure 192, vectors a and c are perpendicular to the X axis, and vectors b and d are parallel to it. Express the projections ax, bx, cx and dx in terms of the absolute values ​​of these vectors or the corresponding numbers.
3. Figure 193 shows the trajectory of a ball moving from point A to point B. Determine: a) the coordinates of the initial and final positions of the ball; b) projections sx and sy of the ball’s displacement; c) modules |sх| and |sy| displacement projections; d) module
4. The boat has moved relative to the pier from point A(-8; -2) to point B(4; 3). Make a drawing, aligning the origin with the pier and indicating points A and B on it. Determine the displacement of the boat AB. Could the path taken by the boat be more complete?
5. It is known that to determine the coordinates of a rectilinearly moving body, the equation x = x0 + sx is used. Prove that the coordinate of a body during its rectilinear uniform motion for any moment of time is determined using the equation x = x0 + vxt
6. Write down an equation to determine the coordinates of a body moving rectilinearly at a speed of 5 m/s along the X axis, if at the moment the observation began its coordinate was 3 m.
7. Two trains - passenger and freight - move along parallel tracks. Relative to the station building, the movement of a passenger train is described by the equation xп = 260 - 10t, and of a freight train by the equation xm = -100 + 8t. Taking the station and trains as material points
8. Tourists go rafting down the river. Figure 194 shows. how the coordinates of the raft change over time relative to the tourist parking area (point O). The beginning of observation coincides with the moment the raft is launched into the water and the beginning of movement. Where the raft was launched
9. A boy slides down a mountain on a sled, moving from a state of rest rectilinearly and uniformly accelerated. In the first 2 s after the start of movement, its speed increases to 3 m/s. After what period of time from the start of movement will the boy’s speed become 4.5 m/
10. Convert the formula to:
11. Based on the fact that derive the formula
12. Figure 27 shows the position of the ball every 0.1 s of its uniformly accelerated fall from rest. The coordinates of all six positions are marked with dashes along the right edge of the ruler. Using the figure, determine the average speed of the ball over the first 0.
13. Two elevators - a regular one and a high-speed one - start moving at the same time and move at uniform acceleration during the same period of time. How many times is the distance covered by a high-speed elevator during this time greater than the distance covered by a conventional elevator?
14. Figure 195 shows a graph of the projection of the elevator speed during acceleration versus time. Draw this graph into a notebook and, using the same coordinate axes, construct a similar graph for a high-speed elevator, the acceleration of which is 3 times greater than the speed of the elevator.
15. A car moves straight along the X axis. The equation for the projection of the car’s velocity vector versus time in SI looks like this: vx = 10 + 0.5t. Determine the magnitude and direction of the initial speed and acceleration of the car. How the Vecto module changes
16. When hit with a stick, the puck acquired an initial speed of 5 m/s and began to slide along the ice with an acceleration of 1 m/s2. Write down the equation for the dependence of the projection of the puck's velocity vector on time and construct a graph corresponding to this equation.
17. It is known that the equation is used to determine the coordinates of a rectilinearly moving body. Prove that the coordinate of a body during its rectilinear uniformly accelerated motion for any moment of time is determined using the equation
18. A skier slides down a mountain, moving in a straight line with a constant acceleration of 0.1 m/s2. Write equations expressing the time dependence of the coordinates and projections of the skier’s velocity vector if his initial coordinates and velocity are zero.
19. A cyclist moves along a highway in a straight line at a speed whose modulus is 40 km/h relative to the ground. A car is moving parallel to it. What can be said about the magnitude of the velocity vector and the direction of motion of the car relative to the ground, if
20. The speed of the boat relative to the water in the river is 5 times greater than the speed of the water flow relative to the shore. Considering the movement of the boat relative to the shore, determine how many times faster the boat moves with the current than against it.
21. A boy holds in his hands a ball with a mass of 3.87 g and a volume of 3 ⋅ 10-3 m3. What will happen to this ball if it is released from your hands?
22. A steel ball rolls uniformly on a horizontal surface and collides with a stationary aluminum ball, as a result of which the aluminum ball receives some acceleration. Can the acceleration modulus of the steel ball be equal to zero? be big
23. Let MZ and RZ be the mass and radius of the globe, respectively, g0 the acceleration of free fall on the Earth’s surface, and g at height h. Based on the formulas, derive the formula:
24. Figure 196 shows balls 1 and 2 of equal mass, tied to threads of length k and 2k, respectively, and moving in circles with the same absolute velocity v. Compare the centripetal accelerations with which the balls move and the tension force
25. Based on the formula for determining centripetal acceleration when moving in a circle and the formula you derived when solving problem 23, obtain the following formula for calculating the first escape velocity at a height h above the Earth’s surface:
26. The average value of the Earth’s radius is 6400 km, and the acceleration of gravity at the Earth’s surface is 9.8 m/s2. Using only these data, calculate the first escape velocity at an altitude of 3600 km above the Earth's surface.
27. Construct a graph of the projection of the velocity vector versus time for a body freely falling for 4 s (v0 = 0, assume g = 10 m/s2).
28. A body weighing 0.3 kg freely falls from rest for 3 s. How much does its momentum increase during the first second of its fall? in the second second of the fall?
29. Using the graph you constructed when solving problem 27, show that the momentum of a freely falling body changes by the same amount over equal periods of time.
30. Aluminum and copper balls of the same volume fall freely from rest from the same height for 2.5 s. The momentum of which ball will be greater and by how many times by the end of the first second of fall? by the end of the second second of the fall? Answers about
31. Two identical billiard balls, moving along the same straight line, collide with each other. Before the collision, the projection of the velocity vector of the first ball onto the X axis was equal to 0.2 m/s, and of the second - 0.1 m/s. Determine the projection of the velocity vector of the second ball
32. Solve the previous problem for the case in which v1x = 0.2 m/s, v2x = -0.1 m/s, v"1x = -0.1 m/s (where v1x and v2x are the projections of the velocity vectors, respectively 1st and 2nd balls before their collision, and v"1x is the projection of the velocity vector of the 1st ball after collisions
33. Using the data and the result of solving problem 32, show that when the balls collide, the law of conservation of total mechanical energy is satisfied.
34. Figure 197 shows how the projection of the velocity vector of one of the swing seat points changes over time. How often does this change occur? What is the frequency of change in the speed of any other point on the swing that is oscillating?
35. A harp string vibrates harmonics with a frequency of 40 Hz. Plot a graph of the coordinate versus time for the midpoint of the string, the vibration amplitude of which is 3 mm. (To plot a graph, we recommend marking the t axis as shown
36. How to achieve the sound of one of two identical tuning forks on sound boxes without touching it? How should the holes of the resonator boxes be positioned in relation to each other? Explain your answers. What physical phenomenon underlies
37. The swing is periodically pushed by hand, i.e. a forcing force acts on it. Figure 199 shows a graph of the dependence of the amplitude of steady-state swing oscillations on the frequency of a given driving force. Using this graph, determine: a) When
38. Figure 200 shows a conductor AB with a length of 10 cm and a mass of 2 g, placed in a uniform magnetic field with an induction of 4 10 2 T perpendicular to the lines of magnetic induction. Electric current flows through the conductor (supplied through thin wires, to the cat
39. An electron flies into a cloud chamber placed in a uniform magnetic field and moves along a circular arc (see the white dashed line in Figure 201). Under the influence of what force does the direction of the electron's velocity change? At what point did he fly into the camera?
40. It is known that the force F with which a uniform magnetic field with induction B acts on a particle with charge e moving at a speed o perpendicular to the magnetic induction lines is determined by the formula: F = Bev. Along an arc of a circle of what radius will there be
41. As a result of what radioactive decay does carbon 146C turn into nitrogen 147N?
42. When aluminum 2713Al nuclei are bombarded by neutrons, an alpha particle is ejected from the resulting nucleus. Write the equation for this reaction.
43. Using the law of conservation of mass and charge numbers, fill in the blank in the entry for the following nuclear reaction: B 105B+ ... → 73Li + 42He.
44. What chemical element is formed as a result of the α-decay of the uranium isotope 23892U? Write down this reaction.
45. As a result of what number of β-decays does the nucleus of a thorium atom 23490Th transform into the nucleus of a uranium atom 23892U?

The force of gravity acts on all bodies on Earth: resting and moving, located on the surface of the Earth and near it.

A body freely falling to the ground moves uniformly accelerated with increasing speed, since its speed is co-directed with the force of gravity and the acceleration of gravity.

A body thrown upward, in the absence of air resistance, also moves with constant acceleration caused by the action of gravity. But in this case, the initial speed v0, which was given to the body during the throw, is directed upward, i.e., opposite to the force of gravity and the acceleration of free fall. Therefore, the speed of the body decreases (for each second - by an amount numerically equal to the module of acceleration of free fall, i.e. by 9.8 m/s).

After a certain time, the body reaches its greatest height and stops at some point, i.e. its speed becomes zero. It is clear that the greater the initial speed of the body when thrown, the longer the rise time will be and the greater the height it will rise by the time it stops.

Then, under the influence of gravity, the body begins to fall down uniformly.

When solving problems on the upward movement of a body under the influence of only gravity, the same formulas are used as for rectilinear uniformly accelerated motion with an initial speed v0, only ax is replaced by gx:

It is taken into account that when moving upward, the velocity vector of the body and the acceleration vector of free fall are directed in opposite directions, therefore their projections always have different signs.

If, for example, the X axis is directed vertically upward, i.e., co-directed with the velocity vector, then v x > 0, which means v x = v, a g x< 0, значит, g x = -g = -9,8 м/с 2 (где v - модуль вектора мгновенной скорости, a g - модуль вектора ускорения).

If the X axis is directed vertically downward, then v x< 0, т. е. v х = -v, a g x >0, i.e. g x = g = 9.8 m/s 2 .

The weight of a body moving under the influence of gravity alone is zero. This can be verified using the experiments shown in Figure 31.

Rice. 31. Demonstration of weightlessness of bodies in free fall

A metal ball is suspended from a homemade dynamometer. According to the readings of the dynamometer at rest, the weight of the ball (Fig. 31, a) is 0.5 N. If the thread holding the dynamometer is cut, then it will fall freely (air resistance in this case can be neglected). At the same time, its pointer will move to the zero mark, indicating that the weight of the ball is zero (Fig. 31, b). The weight of a freely falling dynamometer is also zero. In this case, both the ball and the dynamometer move with the same acceleration, without exerting any influence on each other. In other words, both the dynamometer and the ball are in a state of weightlessness.

In the experiment considered, the dynamometer and the ball fell freely from a state of rest.

Now let’s make sure that the body will be weightless even if its initial speed is not zero. To do this, take a plastic bag and fill it about 1/3 with water; then remove the air from the bag by twisting its upper part into a rope and tying it in a knot (Fig. 31, c). If you take the bag by the lower part filled with water and turn it over, then the part of the bag twisted into a rope under the influence of the weight of the water will unwind and fill with water (Fig. 31, d). If, when turning the bag over, you hold the tourniquet, not allowing it to unwind (Fig. 31, e), and then throw the bag up, then both during the rise and during the fall the tourniquet will not unwind (Fig. 31, f). This indicates that during the flight the water does not exert its weight on the bag, as it becomes weightless.

You can throw this package to each other, then it will fly along a parabolic trajectory. But even in this case, the package will retain its shape in flight, which it was given when thrown.

Questions

1. Does the force of gravity act on a body thrown upward during its ascent?
2. With what acceleration does a body thrown upward move in the absence of friction? How does the speed of the body change in this case?
3. What determines the maximum height of lift of a body thrown upward in the case when air resistance can be neglected?
4. What can be said about the signs of the projections of the vectors of the instantaneous velocity of a body and the acceleration of gravity during the free upward movement of this body?
5. Tell us about the course of the experiments shown in Figure 31. What conclusion follows from them?

Exercise 14

A tennis ball is thrown vertically upward with an initial speed of 9.8 m/s. After what period of time will the speed of the rising ball decrease to zero? How much movement will the ball make from the point of throw?