Laboratory work number 5. Laboratory work in physics

LABORATORY WORK No. 5

DETERMINATION OF MOMENTS OF INERTIA OF BODIES OF ARBITRARY FORM

1 Purpose of work

Determination of the moment of inertia of mathematical and physical pendulums.

2 List of devices and accessories

An experimental setup for determining the moments of inertia of mathematical and physical pendulums, a ruler.

1-physical pendulum,

2-mathematical pendulum,

4-place thread attachment,

5-vertical rack,

6-base,

3 Theoretical part

A material point suspended on a weightless inextensible thread is called a mathematical pendulum. The oscillation period of a mathematical pendulum is determined by the formula:

where l - thread length.

The physical pendulum is called solid, capable of oscillating around a fixed axis that does not coincide with its center of inertia. Oscillations of mathematical and physical pendulums occur under the action of a quasi-elastic force, which is one of the components of gravity.

The reduced length of a physical pendulum is the length of such a mathematical pendulum, in which the oscillation period coincides with the oscillation period of the physical pendulum.

The moment of inertia of a body is a measure of inertia during rotational motion. Its magnitude depends on the distribution of body mass relative to the axis of rotation.

The moment of inertia of a mathematical pendulum is calculated by the formula:

where m - the mass of the mathematical pendulum, l - the length of the mathematical pendulum.

The moment of inertia of a physical pendulum is calculated by the formula:

4 Experiment Results

Determination of the moments of inertia of mathematical and physical pendulums

T m , from	g, m / s 2	I m , kgm 2

m f , kg	T f , from	I f , kgm 2	I, kgm 2

Δ t = 0.001 s

Δ g = 0.05 m / s 2

Δ π = 0,005

Δ m = 0.0005 kg

Δ l = 0.005 m

I f \u003d 0.324 ± 0.007 kg  m 2 ε \u003d 2.104%

Determination of the moment of inertia of a physical pendulum depending on the distribution of mass

						I f , kgm 2	I f , kgm 2

I f 1 \u003d 0.422 ± 0.008 kg  m 2

I f 2 \u003d 0.279 ± 0.007 kg  m 2

I f 3 \u003d 0.187 ± 0.005 kg  m 2

I f 4 \u003d 0.110 ± 0.004 kg  m 2

I f5 \u003d 0.060 ± 0.003 kg  m 2

Conclusion:

In my laboratory work, I learned how to calculate the moment of inertia of a mathematical pendulum and a physical pendulum, which is in some nonlinear dependence on the distance between the suspension point and the center of gravity.

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Laboratory work № 1.

Study of uniformly accelerated motion without initial speed

Objective: to establish the qualitative dependence of the body's speed on time during its uniformly accelerated motion from a state of rest, to determine the acceleration of the body's motion.

Equipment: laboratory chute, carriage, tripod with coupling, stopwatch with sensors.

I have read the rules, I undertake to comply. ________________________

Student signature

Note: During the experiment, the carriage is launched several times from the same position on the chute and its speed is determined at several points at different distances from the initial position.

If the body moves from a state of rest uniformly accelerated, then its movement changes with time according to the law:S = at 2 / 2 (1), and the speed isV = at (2). If we express acceleration from formula 1 and substitute it into 2, then we get a formula expressing the dependence of speed on movement and movement time:V = 2 S/ t.

1. Equally accelerated movement - this is ___

2. In what units in the C system is it measured:

acceleration  and  =  

speed    =  

time  t  =  

moving  s  =  

3. Write the acceleration formula in projections:

and x = _________________.

4. Find the acceleration of the body from the velocity graph.

a \u003d

5. Write the equation of displacement for uniformly accelerated motion.

S \u003d + ______________

If a  0 = 0, then S \u003d

6. The motion is uniformly accelerated if the following law is fulfilled:

S 1 : S 2 : S 3 :…: S n \u003d 1: 4: 9:…: n 2 .

Find an attitudeS 1 : S 2 : S 3 =

Working process

1. Prepare a table to record the results of measurements and calculations:

2. Using a coupling, attach the chute to the tripod at an angle, so that the carriage moves along the chute on its own. Fix one of the stopwatch sensors using a magnetic holder to the chute at a distance of 7 cm from the beginning of the measuring scale (x 1 ). Attach the second sensor opposite to 34 cm on the ruler (x 2 ). Calculate the displacement (S), which the carriage will make when moving from the first sensor to the second

S \u003d x 2 - x 1 = ____________________

3. Place the carriage at the beginning of the groove and release it. Take the stopwatch (t).

4. Calculate the carriage speed (V), with which it moved past the second sensor and the acceleration of movement (a):

______________________________________________________

5. Move the lower probe 3 cm down and repeat experiment (experiment No. 2):

S \u003d ______________________________________________________________

V \u003d _____________________________________________________________

and = ______________________________________________________________

6. Repeat the experiment, removing the lower sensor by another 3 cm (experiment No. 3):

S \u003d

and = _______________________________________________________________

7. Make a conclusion about how the speed of the trolley changes with an increase in the time of its movement, and about what the acceleration of the carriage turned out to be during these experiments.

___________

Laboratory work No. 2.

Measuring the acceleration due to gravity

Objective: to determine the acceleration of gravity, to demonstrate that in free fall the acceleration does not depend on body weight.

Equipment: optoelectric sensors - 2 pcs., steel plate - 2 pcs., measuring unitL-micro, starter platform, power supply.

Safety rules. Read the rules carefully and sign that you agree to follow them.

Caution! There should be no foreign objects on the table. Rough handling of the devices will cause them to fall. At the same time, you can get a mechanical injury, bruise., Remove the devices from working condition.

I have read the rules, I undertake to comply. _________________________

Student signature

Note: To perform the experiment, a demonstration kit "Mechanics" from a series of equipment is usedL-micro.

In this work, the acceleration of gravityg determined based on time measurementt spent by the body to fall from a heighth without initial speed. When conducting an experiment, it is convenient to register the parameters of motion of metal squares of the same size, but different thicknesses and, accordingly, different masses.

Training tasks and questions.

1. In the absence of air resistance, the speed of a freely falling body in the third second of falling increases by:

1) 10 m / s 2) 15 m / s 3) 30 m / s 4) 45 m / s

2. Oh ... Which body at a timet 1 acceleration is zero?

3. The ball is thrown at an angle to the horizon (see picture). If the air resistance is negligible, then the acceleration of the ball at the pointAND co-directional with vector

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

4. The figures show graphs of the dependence of the velocity projection on time for four bodies moving along the axisOh ... Which of the bodies moves with the greatest acceleration in absolute value?

Using the graph of the dependence of the projections of the vectors of displacement of bodies on the time of their movement (see Fig.), Find the distance between the bodies in 3 s after the start of movement.

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

Working process

1. Install the starter platform at the top chalkboard... Place the two optoelectric sensors vertically below it, orienting them as shown in the figure. The sensors are located at a distance of approximately 0.5 m from each other in such a way that a body that freely falls after being released from the launching device passes sequentially through their sections.

2. Connect the optoelectric sensors to the connectors on the trigger platform, and the power supply to the connectors of the connecting cable connected to connector 3 of the measuring unit.

3. Select the item "Determination of the acceleration of gravity (option 1)" in the menu on the computer screen and enter the equipment setup mode. Pay attention to the images of the sensors in the window on the screen. If only a sensor is present, then the sensor is open. When the optical axis of the sensor is overlapped, it is replaced by an image of the sensor with a trolley in its alignment.

4. Hang one of the steel plates from the trigger magnet. In order to use a simple formula when processing the resultsh = gt 2 /2 , you must accurately set mutual arrangement steel plate (in the starting device) and the nearest optoelectric sensor. The belt starts counting when one of the optoelectric sensors is triggered.

5. Move the upper optoelectric sensor up towards the starting device with the body suspended from it until the image of the sensor with the cart in its alignment appears on the screen. Then very carefully lower the sensor down and stop it at the moment when the cart disappears from the image of the sensor ...

Go to the measurement screen and carry out a series of 3 runs. Each time, write down the time that appears on the computer screen.

Measure the distanceh between the optoelectric sensors. Calculate the average time the body fallst wed and substituting the obtained data into the formulag = 2 h / t 2 wed , determine the acceleration of gravityg ... Measure in the same way with another square.

Enter the received data into the table.

Steel plates

Experience number

Distance between sensors

h , m

Time

t , from

Average time

t Wed, s

Acceleration of gravity

g , m / s 2

Large plate

Smaller plate

Draw conclusions based on the experiments:

__________________________

Laboratory work No. 3.

Study of the dependence of the oscillation period of the spring

pendulum from the mass of the load and the stiffness of the spring

Objective: to establish experimentally the dependence of the oscillation period and oscillation frequency of a spring pendulum on the spring stiffness and the mass of the load.

Equipment: set of weights, dynamometer, set of springs, tripod, stopwatch, ruler.

Safety rules. Read the rules carefully and sign that you agree to follow them.

I have read the rules, I undertake to comply .___________________________

Student signature

Practice tasks and questions

1. Sign of oscillatory motion - ___________________

__________________________

2. In which drawings is the body in a position of balance

_______ ________ _________

3. The elastic force is greatest at the point _________ and __________ shown in the figures _______ ________ ________.

4. At each point on the trajectory of movement, except for the point ______, the ball is acted upon by the elastic force of the spring directed to the equilibrium position.

5. Indicate the points where the speed is the highest ____________ and the lowest _______ _______, the highest acceleration ______ ______ and the lowest _______.

X work od

1. Assemble the measuring setup according to the figure.

2. By stretching the spring x and the mass of the load, determine the spring stiffness.

F control \u003d k  x – Hooke's law

F control \u003d R = mg ;

1) ____________________________________________________

2) ____________________________________________________

3) ____________________________________________________

3. Fill in Table 1 of the dependence of the oscillation period on the weight of the load for the same spring.

4. Fill in table No. 2 of the dependence of the oscillation frequency of the spring pendulum on the spring stiffness for a weight of 200 g.

5. Draw conclusions about the dependence of the period and frequency of oscillations of a spring pendulum on the mass and stiffness of the spring.

__________________________________________________________________________________________________

Laboratory work No. 4

Study of the dependence of the period and frequency of free oscillations of a thread pendulum on the length of the thread

Objective: find out how the period and frequencies of free oscillations of a filament pendulum depend on its length.

Equipment:a tripod with a clutch and a foot, a ball about 130 cm long with a thread attached to it, a stopwatch.

Safety rules. Read the rules carefully and sign that you agree to follow them.

Caution! There should be no foreign objects on the table. Use the devices only for their intended purpose. Rough handling of the devices will cause them to fall. At the same time, you can get a mechanical injury, bruise, remove the devices from working condition.

I have read the rules, I undertake to comply. _______________________

Student signature

Practice tasks and questions

1. What vibrations are called free? ___________________________

________________________________________________________________

2. What is a filament pendulum? ___________________________

________________________________________________________________

3. The oscillation period is ___________________________________________

________________________________________________________________

4. The vibration frequency is ___________________________________________

5. The period and frequency are _______________________ values, since their products are equal to ___________________.

6. In what units in the C system is it measured:

period [ T] =

frequency [ν] \u003d

7. The thread pendulum made 36 complete oscillations in 1.2 minutes. Find the period and frequency of the pendulum.

Given: B Solution:

t \u003d 1.2 minutes \u003d T =

N = 36

T - ?, ν - ?

Working process

1. Place a tripod on the edge of the table.

2. Secure the string of the pendulum to the tripod foot using a piece of eraser or thick paper.

3. For the first experiment, select a thread length of 5 - 8 cm and deflect the ball from the equilibrium position by a small amplitude (1 - 2 cm) and release.

4. Measure the span of time t , during which the pendulum will make 25 - 30 complete oscillations ( N ).

5. Record the measurement results in the table

6. Conduct 4 more experiments in the same way as the first, with the length of the pendulum L increase to the limit.

(For example: 2) 20 - 25 cm, 3) 45 - 50 cm, 4) 80 - 85 cm, 5) 125 - 130 cm).

7. For each experiment, calculate the period of oscillation and write it down in the table.

T 1 = T 4 =

T 2 = T 5 =

T 3 =

8
. For each experiment, calculate the value of the vibration frequency or

and write it down in the table.

9. Analyze the results recorded in the table and answer the questions.

a) Did you increase or decrease the length of the pendulum if the oscillation period decreased from 0.3 s to 0.1 s?

________________________________________________________________________________________________________________________________

b) Increased or decreased the length of the pendulum, if the frequency of oscillations decreased from 5 Hz to 3 Hz

____________________________________________________________________________________________________________________________________

Laboratory work No. 5.

Study of the phenomenon of electromagnetic induction

Objective: study the phenomenon of electromagnetic induction.

Equipment:milliammeter, coil-coil, arc-shaped or strip magnet, power source, coil with an iron core from a collapsible electromagnet, rheostat, key, connecting wires.

Safety rules. Read the rules carefully and sign that you agree to follow them.

Caution! Protect appliances from falling. Avoid extreme loads measuring instruments... When conducting experiments with magnetic fields, take off the watch and remove the mobile phone.

________________________

Student signature

Practice tasks and questions

1. Magnetic field induction is ______________________________________

characteristic of the magnetic field.

2. Write down the formula modulus of the vector of magnetic induction.

B \u003d __________________.

The unit of measurement of magnetic induction in the C system: IN  =  

3. What is magnetic flux? _________________________________________

_________________________________________________________________

4. What does the magnetic flux depend on? ____________________________________

_________________________________________________________________

5. What is the phenomenon of electromagnetic induction? _________________

_________________________________________________________________

6. Who discovered the phenomenon of electromagnetic induction and why is this discovery classified as the greatest? ______________________________________

__________________________________________________________________

Working process

1. Connect the coil to the milliammeter clamps.

2. Insert one of the poles of the magnet into the coil, and then stop the magnet for a few seconds. Write down whether an induction current occurred in the coil: a) during the movement of the magnet relative to the coil; b) during its stop.

__________________________________________________________________________________________________________________________________

3. Record if the magnetic flux has changedF penetrating the coil: a) during the movement of the magnet; b) during its stop.

4. Formulate under what condition an induction current occurred in the coil.

5 . Insert one of the poles of the magnet into the coil, and then remove at the same speed. (Adjust the speed so that the pointer deviates to half the full scale value.)

________________________________________________________________

__________________________________________________________________

6. Repeat the experiment, but with a higher speed of the magnet.

a) Write down the direction of the induction current. ______________

_______________________________________________________________

b) Write down what the induction current module will be. __________________

_________________________________________________________________

7. Write down how the speed of the magnet moves:

a) By the amount of change in magnetic flux .__________________________

__________________________________________________________________

b) On the induction current module. ____________________________________

__________________________________________________________________

8. Formulate how the modulus of the induction current depends on the rate of change of the magnetic flux.

_________________________________________________________________

9. Assemble the setup for the drawing experiment.

1 - coil-coil

2 - coil

10. Check if there is a1 induction current at: a) closing and opening the circuit in which the coil is included2 ; b) flowing through2 direct current; c) changing the current strength with a rheostat.

________________________________________________________________________________________________________________________________

11. Write down in which of the following cases: a) the magnetic flux through the coil changed1 ; b) there was an induction current in the coil1 .

Conclusion:

________________________________________________________________________________________________________________________________________

Laboratory work No. 6

Observation of continuous and line spectra

emitting

Objective:observation of a continuous spectrum using glass plates with beveled edges and a line emission spectrum using a two-tube spectroscope.

Equipment:projection apparatus, two-tube spectroscope spectral tubes with hydrogen, neon or helium, high-voltage inductor, power supply, (these devices are common for the whole class), glass plate with beveled edges (issued to each).

Description of the device.

Caution! Electricity! Make sure that the insulation of the conductors is intact. Avoid extreme loads on measuring instruments.

I have read the rules, I undertake to comply. ______________________

Student signature

Practice tasks and questions

1. The spectroscope was designed in 1815 by a German physicist

________________________________________________________

2. The visible light is electromagnetic waves frequency:

from _________________ Hz to __________________ Hz.

3. What bodies emit a continuous spectrum?

1. ______________________________________________________________

2. ______________________________________________________________

3. ______________________________________________________________

4. What is the spectrum of low-density luminous gases?

________________________________________________________________

5. Formulate the law of H. Kirchhoff: _________________________________

_______________________________________________________________

Working process

1. Place the plate horizontally in front of the eye. Observe a light vertical strip on the screen through the edges making up an angle of 45º - the image of the sliding slit of the projection device.

2. Select the primary colors of the obtained continuous spectrum and record them in the observed sequence.

________________________________________________________________

3. Repeat the experiment, looking at the strip through the 60 ° angle. Record differences as spectra.

________________________________________________________________

4. Observe line spectra of hydrogen, helium, or neon by viewing luminous spectral tubes with a spectroscope.

Write down which lines were seen.

__________________________________________________________________

Conclusion: ____________________________________________________________

__________________________________________________________________

Laboratory work No. 7

Study of nuclear fission in uranium

track photos

Objective: verify the validity of the law of conservation of momentum using the example of uranium fission.

Equipment: photograph of tracks of charged particles formed in a photographic emulsion during fission of a uranium atom nucleus under the action of a neutron, measuring ruler.

Note: the figure shows a photograph of the division of the nucleus of a uranium atom under the action of a neuron into two fragments (the nucleus was at the pointg ). The tracks show that the fragments of the uranium atom nucleus scattered in opposite directions (the break in the left track is explained by the collision of the fragment with the nucleus of one of the atoms of the emulsion). The greater the particle energy, the longer the track length. The thickness of the track is the greater, the greater the charge of the particle and the lower its velocity.

Practice tasks and questions

1. Formulate the law of conservation of momentum. ___________________________

__________________________________________________________________

2. Explain the physical meaning of the equation:

__________________________________________________________________

3. Why does the uranium fission reaction go with the release of energy in environment? _______________________________________________

_______________________________________________________________

4. Using the example of any reaction, explain what the laws of conservation of charge and mass number are. _________________________________

_________________________________________________________________

5. Find the unknown element in the periodic table, formed by the following β-decay reaction:

__________________________________________________________________

6. What is the principle of action of a photographic emulsion?

______________________________________________________________

Working process

1. Look at the photo and find the shard tracks.

2. Measure the track lengths of the debris with a millimeter ruler and compare.

3. Using the law of conservation of momentum, explain why the fragments formed during the fission of the uranium atom nucleus flew in opposite directions. _____________________________________

_________________________________________________________________

4. Are the charges and energy of the fragments the same? _____________________________

__________________________________________________________________

5. On what grounds can you judge this? ________________________

__________________________________________________________________

6. One of the possible reactions of uranium fission can be written symbolically as follows:

where z x – the nucleus of an atom of one of the chemical elements.

Using the law of conservation of charge and the table of D.I. Mendeleev, determine what kind of element it is.

____________________________________________________________________________________________________________________________________

Conclusion: ______________________________________________________________

____________________________________________________________________________________________

Laboratory work No. 8

Studying tracks of charged particles by ready

photos

Objective:explain the nature of the motion of charged particles.

Equipment:photographs of tracks of charged particles obtained in a Wilson chamber, a bubble chamber and a photographic emulsion.

Practice tasks and questions

1. What methods of studying charged particles do you know? _____________

________________________________________________________________________________________________________________________________________________________________________________________________

2. What is the principle of the Wilson chamber? ___________________

________________________________________________________________________________________________________________________________

3. What is the advantage of a bubble chamber over a Wilson chamber? How are these devices different? _________________________________________

________________________________________________________________________________________________________________________________________________________________________________________________

4. What are the similarities between the photoemulsion method and photography?

________________________________________________________________________________________________________________________________________________________________________________________________

5. Formulate the left hand rule for determining the direction of the force acting on a charge in a magnetic field. ____________________________

________________________________________________________________________________________________________________________________________________________________________________________________

6. The figure shows the track of a particle in a Wilson chamber placed in a magnetic field. The vector is directed from the plane. Determine the sign of the particle charge.

______________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Working process

1. Which photographs presented to you (Fig. 1, 2, 3) show the tracks of particles moving in a magnetic field? Justify the answer.

______________________________________________________________________________________________________

Figure: 1

__________________________________

2. Consider a photograph of the tracks of alpha particles moving in the Wilson chamber (Fig. 1).

a) In what direction did the alpha particles move?

__________________________________________________________________________________________________________________________________________________________________________

b) Why are the lengths of the tracks of alpha particles approximately the same?

______________________________________________________________________________________________________

Figure: 3

__________________________________

c) Why does the thickness of the tracks of α-particles increase slightly by the end of the motion? _________________________________________________________

________________________________________________________________________________________________________________________________

3. Figure 2 shows a photograph of alpha-particle tracks in a Wilson chamber in a magnetic field. Answer the following questions.

a) In which direction did the particles move? _____________________________

________________________________________________________________________________________________________________________________

b) How was the magnetic induction vector directed? ___________________

________________________________________________________________________________________________________________________________

c) Why did the radius of curvature and the thickness of the tracks change as the α particles moved? _______________________________________________________

________________________________________________________________________________________________________________________________

4. Figure 3 shows a photograph of an electron track in a bubble chamber in a magnetic field. Answer the following questions.

a) Why does the electron track have a spiral shape? _____________________

________________________________________________________________________________________________________________________________

b) In which direction was the electron moving? __________________________

________________________________________________________________________________________________________________________________

c) How was the magnetic induction vector directed? ___________________

________________________________________________________________________________________________________________________________

d) What could be the reason that the track of the electron in Figure 3 is much longer than the tracks of α-particles in Figure 2? _______________________

________________________________________________________________________________________________________________________________

Conclusion: _________________________________________________________

______________________________________________________________________________________________________________________________________________________________________________________________________

Laboratory work No. 9

Measurement of natural background radiation

dosimeter

Objective:gaining practical skills in using a household dosimeter to measure background radiation.

Equipment:household dosimeter, instructions for its use.

Safety rules. Read carefully the rules for using the dosimeter and sign that you agree to follow them. Caution! Protect the device from falling.

I have read the rules, I undertake to comply. _______________________ (_ student's signature)

Note:household dosimeters are designed for operational individual monitoring of the radiation situation by the population and allow an approximate estimate of the equivalent radiation dose rate. Most modern dosimeters measure the radiation dose rate in microsieverts per hour (μSv / h), but another unit is still widely used - micro-roentgen per hour (μR / h). The ratio between them is as follows: 1 μSv / h \u003d 100 μR / h. The average value of the equivalent dose of absorbed radiation due to the natural background radiation is about 2mSv per year.

Practice tasks and questions

1. The absorbed dose of radiation is __________________________________

________________________________________________________________________________________________________________________________________________________________________________________________

2. Absorbed dose formula:

r de: ________________________________

___________________________________

3. Absorbed dose units: \u003d

4. The equivalent dose H is determined by the formula:

where: ________________________________

___________________________________

5. The unit of measure for the equivalent dose is ____________________

6. How many times will the initial number of radioactive nuclei decrease in a time equal to the half-life? ______________________________________

Working process

1. Carefully study the instructions for working with the dosimeter and determine:

what is the procedure for preparing it for work;

what types of ionizing radiation it measures;

in what units the device registers the radiation dose rate;

what is the duration of the measurement cycle;

what are the limits of the absolute measurement error;

what is the procedure for monitoring and replacing the internal power source;

what is the location and purpose of the controls for the operation of the device.

2. Carry out an external examination of the device and test it on.

3. Make sure the dosimeter is in working order.

4. Prepare the device for measuring the radiation dose rate.

5. Measure the background radiation level 8 - 10 times, recording each time the reading of the dosimeter.

6. Calculate the average background radiation.

________________________________________________________________________________________________________________________________

7. Calculate what dose of ionizing radiation a person will receive during the year if the average value of the background radiation does not change throughout the year. Compare it with a value that is safe for human health.

________________________________________________________________________________________________________________________________

8. Compare the obtained average background value with the natural radiation background taken as the norm - 0.15 μSv / h.

Make a conclusion _________________________________________________

_______________________________________________________________

________________________________________________________________

Physics is the science of nature. As a school subject, it occupies a special place, because, along with cognitive information about the world around us, it develops logical thinking, forms a materialistic worldview, creates a holistic picture of the universe, has an educational function.

The role of 7th grade physics in the formation of personality, regardless of the profession chosen by a person, is enormous and continues to grow. In many countries, physics as a discipline began to be introduced into the programs of humanitarian universities. Deep knowledge of physics is a guarantee of success in any profession.

Mastering physics is most effective through activity. The acquisition (consolidation) of knowledge in physics in the 7th grade is facilitated by:

1) decision of physical tasks of various types;
2) analysis of daily events from the standpoint of physics.

Present reshebnik on physics for grade 7 to the textbook of the authors L.A. Isachenkova, Yu.D. Leshchinsky 2011 year of publication provides ample opportunities in such a type of activity as solving problems, presenting design, experimental problems, problems with a choice of answers and problems with unfinished conditions.

Each type of task has a certain methodological load. So, tasks with unfinished conditions invite the student to become a co-author of the problem, supplement the condition and solve the problem in accordance with their level of training. This type of problem actively develops the creativity of students. Questions-tasks develop thinkingteach the student to see physical phenomena in everyday life.

Applications carry important information both for solving the problems given in the Manual, and for solving everyday tasks of a household nature. In addition, the analysis of reference data develops thinking, helps to establish the relationship between the properties of substances, and allows you to compare scales physical quantities, characteristics of devices and machines.

But the main objective of this manual - to teach the reader to independently acquire knowledge, through solving problems of various types, to deepen the understanding of physical phenomena and processes, to master the laws and patterns that connect physical quantities.

We wish you success on the difficult path of learning physics.

Laboratory work No. 1

The movement of a body in a circle under the influence of gravity and elasticity.

Objective:check the validity of Newton's second law for the motion of a body in a circle under the action of several.

1) weight, 2) thread, 3) tripod with coupling and ring, 4) sheet of paper, 5) Measuring tape, 6) watch with second hand.

Theoretical justification

The experimental setup consists of a weight tied to a tripod ring on a string (Fig. 1). A sheet of paper is placed on the table under the pendulum, on which a circle with a radius of 10 cm is drawn. Center ABOUT the circle is on the vertical below the suspension point TO pendulum. When the load moves along the circle shown on the sheet, the thread describes a conical surface. Therefore, such a pendulum is called conical.

Let's project (1) onto the X and Y axes.

(X), (2)

(Y), (3)

where is the angle formed by the thread with the vertical.

Let us express from the last equation

and substitute it into equation (2). Then

If the circulation period T pendulum in a circle of radius K is known from experimental data, then

the period of circulation can be determined by measuring the time t , for which the pendulum commits N revolutions:

As can be seen from Figure 1,

, (7)

Fig. 1

Fig. 2

where h \u003d OK - distance from suspension point TO to the center of the circle ABOUT .

Taking into account formulas (5) - (7), equality (4) can be represented as

. (8)

Formula (8) is a direct consequence of Newton's second law. Thus, the first way to check the validity of Newton's second law is reduced to an experimental check of the identity of the left and right sides of equality (8).

Force imparts centripetal acceleration to the pendulum

Taking into account formulas (5) and (6), Newton's second law has the form

. (9)

Power F measured with a dynamometer. The pendulum is pulled from the equilibrium position by a distance equal to the radius of the circle R , and take readings of the dynamometer (Fig. 2) Weight of the load m supposed to be known.

Consequently, another way to test the validity of Newton's second law is reduced to an experimental test of the identity of the left and right sides of equality (9).

order of work

Assemble the experimental setup (see Fig. 1), choosing a pendulum length of about 50 cm.

On a piece of paper, draw a circle with a radius R \u003d 10 cm

Position the sheet of paper so that the center of the circle is under the vertical suspension point of the pendulum.

Measure the distance h between suspension point TO and the center of the circle ABOUT centimeter tape.

h \u003d

5. Move the conical pendulum along the drawn circle at a constant speed. Measure the time t , during which the pendulum performs N \u003d 10 turns.

t =

6. Calculate the centripetal acceleration of the load

Calculate

Conclusion.

Laboratory work No. 2

Boyle-Marriott's Law Test

Objective: experimentally verify the Boyle - Mariotte law by comparing gas parameters in two thermodynamic states.

Equipment, measuring instruments: 1) instrument for studying gas laws, 2) a barometer (one per class), 3) a laboratory stand, 4) a strip of graph paper 300 * 10 mm, 5) a measuring tape.

Theoretical justification

Boyle's Law - Mariotte determines the relationship between the pressure and volume of a gas of a given mass at a constant gas temperature. To make sure that this law or equality is true

(1)

just measure the pressurep 1 , p 2 gas and its volumeV 1 , V 2 in the initial and final state, respectively. An increase in the accuracy of checking the law is achieved by subtracting the product from both sides of equality (1). Then formula (1) will have the form

(2)

(3)

The device for studying gas laws consists of two glass tubes 1 and 2 50 cm long, connected to each other by a rubber hose 3 1 m long, plates with clamps 4 measuring 300 * 50 * 8 mm and plugs 5 (Fig. 1, a). A strip of graph paper is attached to plate 4 between the glass tubes. Tube 2 is removed from the base of the device, lowered down and fixed in the leg of the tripod 6. The rubber hose is filled with water. Atmospheric pressure is measured by a barometer in mm Hg. Art.

When fixing the movable tube in the initial position (Fig. 1, b), the cylindrical volume of gas in the fixed tube 1 can be found by the formula

, (4)

where S - cross-sectional area of \u200b\u200bthe tube 1u

The initial gas pressure in it, expressed in mm Hg. Art., consists of atmospheric pressure and the pressure of a column of water with a height in the tube 2:

mmHg. (five).

where is the difference in water levels in the tubes (in mm). Formula (5) takes into account that the density of water is 13.6 times less than the density of mercury.

When the tube 2 is lifted up and fixed in its final position (Fig. 1, c), the volume of gas in the tube 1 decreases:

(6)

where is the length of the air column in the fixed tube 1.

The final gas pressure is found by the formula

mm. rt. Art. (7)

Substitution of the initial and final gas parameters into formula (3) makes it possible to represent the Boyle - Mariotte law in the form

(8)

Thus, checking the validity of the Boyle - Mariotte law is reduced to an experimental check of the identity of the left Л 8 and the right П 8 parts of equality (8).

Work order

7.Measure the difference in water levels in the tubes.

Lift the movable tube 2 even higher and fix it (see Fig. 1, c).

Repeat the measurement of the length of the air column in tube 1 and the difference in water levels in the tubes. Record your measurements.

10. Measure the atmospheric pressure with a barometer.

11. Calculate the left side of equality (8).

Calculate the right side of equality (8).

13. Check the fulfillment of equality (8)

CONCLUSION:

Laboratory work No. 4

Mixed conductor connection study

Objective : experimentally study the characteristics of a mixed connection of conductors.

Equipment, measuring instruments: 1) power supply, 2) key, 3) rheostat, 4) ammeter, 5) voltmeter, 6) connecting wires, 7) three wire resistors with resistances of 1 Ohm, 2 Ohm and 4 Ohm.

Theoretical justification

Many electrical circuits use a mixed connection of conductors, which is a combination of series and parallel connections. The simplest mixed connection of resistances = 1 ohm, \u003d 2 ohm, \u003d 4 ohm.

a) Resistors R 2 and R 3 are connected in parallel, so the resistance between points 2 and 3

b) In addition, with a parallel connection, the total current flowing into node 2 is equal to the sum of the currents flowing from it.

c) Given that the resistanceR 1 and an equivalent resistance are connected in series.

, (3)

and the total resistance of the circuit between points 1 and 3.

.(4)

The electrical circuit for studying the characteristics of the mixed connection of conductors consists of a power source 1, to which a rheostat 3, an ammeter 4 and a mixed connection of three wire resistors R 1, R 2 and R 3 are connected through a switch 2. A voltmeter 5 measures the voltage between different pairs of points in the circuit. The electric circuit diagram is shown in Figure 3. Subsequent measurements of the current and voltage in the electric circuit will allow checking the relationships (1) - (4).

Current measurementsIflowing through the resistorR1, and the equality of potentials on it allows you to determine the resistance and compare it with a given value.

. (5)

Resistance can be found from Ohm's law by measuring the potential difference with a voltmeter:

.(6)

This result can be compared with the value obtained from formula (1). The validity of formula (3) is checked by an additional measurement using a voltage voltmeter (between points 1 and 3).

This measurement will also allow you to estimate the resistance (between points 1 and 3).

.(7)

The experimental values \u200b\u200bof the resistances obtained by formulas (5) - (7) must satisfy the ratio 9;) for a given mixed connection of conductors.

Work order

Assemble the electrical circuit

3. Record the current measurement.

4. Connect a voltmeter to points 1 and 2 and measure the voltage between these points.

5. Make a note of the voltage measurement

6. Calculate the resistance.

7. Record the measurement of resistance \u003d and compare it with the resistance of the resistor \u003d 1 ohm

8. Connect a voltmeter to points 2 and 3 and measure the voltages between these points

check the validity of formulas (3) and (4).

Ohm

Conclusion:

We have experimentally studied the characteristics of a mixed conductor connection.

Let's check:

Additional task.Make sure that when the conductors are connected in parallel, the equality is true:

Ohm

2 course.

Laboratory work No. 1

Study of the phenomenon of electromagnetic induction

Objective: to prove experimentally Lenz's rule, which determines the direction of the current in electromagnetic induction.

Equipment, measuring instruments: 1) arc-shaped magnet, 2) coil-coil, 3) milliammeter, 4) strip magnet.

Theoretical justification

According to the law of electromagnetic induction (or the Faraday-Maxwell law), the EMF of electromagnetic induction E i in a closed loop is numerically equal and opposite in sign to the rate of change of the magnetic flux F through the surface bounded by this contour.

E i \u003d - Ф '

To determine the sign of the induction EMF (and, accordingly, the direction of the induction current) in the loop, this direction is compared with the selected direction of the loop bypass.

The direction of the induction current (as well as the value of the induction EMF) is considered positive if it coincides with the selected direction of the loop bypass, and is considered negative if it is opposite to the selected direction of the loop bypass. Let us use the Faraday - Maxwell law to determine the direction of the induction current in a circular wire loop with an area S 0 ... Suppose that at the initial moment of time t 1 =0 the induction of the magnetic field in the area of \u200b\u200bthe loop is zero. The next moment in time t 2 = the loop moves into the area of \u200b\u200bthe magnetic field, the induction of which is directed perpendicular to the plane of the loop towards us (Fig. 1 b)

For the direction of traversing the contour, we choose the direction clockwise. According to the gimbal's rule, the contour area vector will be directed from us perpendicular to the contour area.

The magnetic flux penetrating the loop at the initial position of the loop is zero (\u003d 0):

Magnetic flux at the end position of the coil

Change in magnetic flux per unit of time

This means that the EMF of induction, according to formula (1), will be positive:

E i \u003d

This means that the induction current in the circuit will be directed clockwise. Accordingly, according to the rule of thumb for loop currents, the self-induction on the axis of such a loop will be directed against the induction of the external magnetic field.

According to Lenz's rule, the induction current in the circuit has such a direction that the magnetic flux created by it through the surface bounded by the circuit prevents the change in the magnetic flux that caused this current.

The induction current is also observed when the external magnetic field is amplified in the plane of the loop without moving it. For example, when a strip magnet moves into a loop, the external magnetic field and the magnetic flux that penetrates it increase.

Loop traversal direction

F 1

F 2

ξ i

(sign)

(ex.)

I A

B 1 S 0

B 2 S 0

- (B 2 –B 1) S 0<0

15 mA

Work order

1. Connect the coil - uterus 2 (see Fig. 3) to the terminals of the milliammeter.

2. Insert the north pole of the arched magnet into the coil along its axis. In subsequent experiments, move the poles of the magnet on the same side of the coil, the position of which does not change.

Check the compliance of the test results with Table 1.

3. Remove the arched magnet's north pole from the coil. Present the results of the experiment in the table.

Loop traversal directionmeasure the refractive index of the glass with a plane-parallel plate.

Equipment, measuring instruments:1) a plane-parallel plate with beveled edges, 2) a measuring ruler, 3) a student's square.

Theoretical justification

The method of measuring the refractive index using a plane-parallel plate is based on the fact that a beam passing through a plane-parallel plate leaves it parallel to the direction of incidence.

According to the law of refraction, the refractive index of the medium is

To calculate and on a sheet of paper, two parallel straight lines AB and CD are drawn at a distance of 5-10 mm from each other and a glass plate is placed on them so that its parallel edges are perpendicular to these lines. With this arrangement of the plate, parallel straight lines do not move (Fig. 1, a).

Place the eye at the level of the table and, following the straight lines AB and CD through the glass, turn the plate counterclockwise around the vertical axis (Fig. 1, b). The rotation is carried out until the QC beam appears to be an extension of BM and MQ.

To process the measurement results, draw the contours of the plate with a pencil and remove it from the paper. Through point M, a perpendicular O 1 O 2 is drawn to the parallel edges of the plate and the line MF.

Then, equal segments ME 1 \u003d ML 1 are laid on the straight lines BM and MF, and the perpendiculars L 1 L 2 and E 1 E 2 are lowered with the help of a square from points E 1 and L 1 onto the line O 1 O 2. Of right triangles L

a) first orient the parallel edges of the plate perpendicular to AB and CD. Make sure the parallel lines do not move.

b) place the eye at the level of the table and, following the lines AB and CD through the glass, turn the plate counterclockwise around the vertical axis until the QC beam appears to be a continuation of BM and MQ.

2. Draw the outline of the record with a pencil, and then remove it from the paper.

3. Through point M (see Fig. 1, b), draw a perpendicular О 1 О 2 to the parallel edges of the plate and line МF (continuation МQ) using a square.

4.Center at point M, draw a circle of arbitrary radius, mark points L 1 and E 1 on lines BM and MF (ME 1 \u003d ML 1)

5. Using a square, lower the perpendiculars from points L 1 and E 1 to the line O 1 O 2.

6. Measure the length of the segments L 1 L 2 and E 1 E 2 with a ruler.

7. Calculate the refractive index of the glass using Equation 2.