Lesson rectilinear and curvilinear motion. Types of mechanical movement (rectilinear and curvilinear). Why choose not to consider relocation

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Lesson topic: Rectilinear and curvilinear motion. The movement of the body in a circle.

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Mechanical motion Rectilinear Curvilinear Ellipse motion Parabolic motion Hyperbolic motion Circular motion

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Lesson objectives: 1. Know the main characteristics of curvilinear motion and the relationship between them. 2. Be able to apply the acquired knowledge in solving experimental problems.

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Topic study plan

The study of new material The condition of rectilinear and curvilinear motion Direction of body velocity during curvilinear motion Centripetal acceleration Period of revolution Frequency of revolution Centripetal force Performing frontal experimental tasks Independent work in the form of tests Summing up

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According to the type of trajectory, the movement is: Curvilinear Rectilinear

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Conditions for rectilinear and curvilinear motion of bodies (Experiment with a ball)

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p.67 Remember! Working with the textbook

Slide 9

Circular motion - a special case of curvilinear motion

Slide 10

Movement characteristics - linear speed of curvilinear movement () - centripetal acceleration () - period of revolution () - frequency of revolution ()

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Remember. The direction of particle motion coincides with the tangent to the circle

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With curvilinear motion, the speed of the body is directed tangentially to the circle. Remember.

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With curvilinear motion, acceleration is directed towards the center of the circle. Remember.

Slide 14

Why is the acceleration directed towards the center of the circle?

slide 15

Definition of speed - speed - period of revolution r - radius of the circle

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When a body moves in a circle, the modulus of the velocity vector can change or remain constant, but the direction of the velocity vector necessarily changes. Therefore, the velocity vector is a variable value. This means that the movement in a circle always occurs with acceleration.

Remember!

Slide 17

Centripetal force elastic force friction force gravitational force Hydrogen atom model

Slide 18

1. Set the dependence of the speed on the radius2. Measure the acceleration while moving in a circle3. Determine the dependence of centripetal acceleration on the number of revolutions per unit time.

Experiment

Slide 19

Option 1Option 2 1. The body moves uniformly in a circle in a clockwise direction counterclockwise How is the acceleration vector directed during such a movement? a) 1; b) 2; in 3 ; d) 4. 2. The car moves with a constant modulo speed along the trajectory of the figure. At which of the indicated points of the trajectory is the centripetal acceleration the minimum maximum? 3. How many times will centripetal acceleration change if the speed of a material point is increased and decreased by 3 times? a) will increase by 9 times; b) decrease by 9 times; c) will increase by 3 times; d) will decrease by 3 times. Independent work

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Continue the sentence Today in the lesson, I realized that ... I liked the lesson that ... In the lesson I was pleased ... I am satisfied with my work because ... I would like to recommend ...

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Homework: §18-19, ex. 18 (1, 2) Additional control. 18 (5) Thank you for your attention. Thank you for the lesson!

View all slides

MBOU "Chubaevskaya OOSh" Urmarsky district of the Chechen Republic

PHYSICS LESSON IN GRADE 9

Rectilinear and curvilinear motion.

Movement of a body in a circle.

Teacher: Stepanova E.A.

Chubaevo - 2013

Topic: Rectilinear and curvilinear motion. The movement of a body in a circle with a constant modulo speed.

Lesson objectives: to give students an idea of rectilinear and curvilinear motion, frequency, period. To acquaint with the formulas for finding these quantities and units of measurement.
Educational tasks: to form the concept of rectilinear and curvilinear motion, the quantities characterizing it, the units of measurement of these quantities and formulas for calculation.
Developmental tasks: to continue the formation of skills to apply theoretical knowledge to solve practical problems, to develop interest in the subject and logical thinking.
Educational tasks: continue to develop the horizons of students; the ability to keep notes in notebooks, to observe, to notice the patterns of phenomena, to argue their conclusions.

Equipment: Presentation.Computer. Multimedia projector Ball, ball on string, inclined chute, ball, toy car, spinning top, clock model with arrows, stopwatches

During the classes

I. Organizing time. Introductory word of the teacher. Hello, my young friends! Let me start our today's lesson with these lines: "Mysteries of terrible nature hang everywhere in the air" (N. Zabolotsky, poem "Mad Wolf") (slide 1)

2. Knowledge update

What types of movement do you know?What is the difference between rectilinear and curvilinear movements?- Compare toolpath and path for rectilinear and curvilinear motions. Teacher: We know that all bodies attract each other. In particular, the Moon, for example, is attracted to the Earth. But the question arises: if the Moon is attracted to the Earth, why does it revolve around it, and not fall to the Earth? (sl-)

In order to answer this question, it is necessary to consider the types of motion of bodies. We already know that movement can be uniform and uneven, but there are other characteristics of movement. (slide)

3. Problem situation: How are the following movements different?

Demonstrations: ball falling in a straight line, ball rolling down a straight chute. And along a circular path, the rotation of a ball on a thread, the movement of a toy car on the table, the movement of a ball thrown at an angle to the horizon ... ( by type of trajectory)

Teacher: According to the type of trajectory, these movements can be divide for movements in a straight line and along a curved line .(slide)

Let's try to give definitions curvilinear and rectilinear movements. ( Writing in a notebook) rectilinear motion- movement in a straight line. Curvilinear movement - movement along an indirect (curved) trajectory.

4. So, the topic of the lesson

Rectilinear and curvilinear motion. Circular motion(slide)

Teacher: Consider two examples of curvilinear movement: along a broken line and along a curve (draw). How are these trajectories different?

Pupils: In the first case, the trajectory can be divided into straight sections and consider each section separately. In the second case, you can split the curve into arcs of circles and straight sections. T.ob. this movement can be considered as a sequence of movements occurring along the arcs of circles of different radii. Therefore, in order to study curvilinear motion, one must study circular movement.(slide 15)

Message 1 The movement of the body in a circle

In nature and technology very often there are movements whose trajectories are not straight, but curved lines. This is a curvilinear movement. Planets and artificial satellites of the Earth move along curvilinear trajectories in outer space, and on Earth all kinds of means of transport, parts of machines and mechanisms, river waters, atmospheric air, etc.

If you press the end of a steel rod against a rotating grindstone, then the hot particles coming off the stone will be visible in the form of sparks. These particles fly at the same speed that they had at the moment of separation from the stone. It is clearly seen that the direction of movement of the sparks coincides with the tangent to the circle at the point where the rod touches the stone. Tangent moving spray from the wheels of a skidding car. (Draw.)

Direction and modulus of speed

Account: In this way, instantaneous speed body at different points of the curvilinear trajectory has a different direction. Modulo, the speed can be the same everywhere or change from point to point. (slide)

But even if the modulus of speed does not change, it cannot be considered constant. Speed is a vector quantity. For a vector quantity, the modulus and direction are equally important. And times changing speed, so there is an acceleration. Therefore, curvilinear motion is always acceleration, even if modulo the speed is constant .(slide)(video1)

Acceleration a body moving uniformly in a circle at any point centripetal, i.e. directed along the radius of the circle towards its center. At any point, the acceleration vector is perpendicular to the velocity vector. (Draw)

Centripetal acceleration module: a c \u003d V 2 / R ( write a formula), where V is the linear velocity of the body, and R is the radius of the circle. (slide)

Centripetal force - the force acting on the body during curvilinear motion at any time, is always directed along the radius of the circle to the center (as well as centripetal acceleration). The force acting on the body is proportional to the acceleration. F=ma, then

Characteristics of the movement of the body in a circle

Movement in a circle is often characterized not by the speed of movement, but by the time interval during which the body makes one complete revolution. This value is called circulation period and is denoted by the letter T. ( Write period definition). When moving in a circle, the body will return to its original point in a certain period of time. Therefore, circular motion is periodic.

Period is the time of one complete rotation.

If the body makes N revolutions in time t, how to find the period? (formula)

Let's find the relationship between the period of revolution T and the modulus of speed for uniform motion along a circle of radius R. V \u003d S / t \u003d 2πR / T. ( Write the formula in your notebook)

Message2 A period is a value that occurs frequently enough in nature and technology. Yes, we know. That the Earth rotates on its axis and the average period of rotation is 24 hours. The complete revolution of the Earth around the Sun takes about 365.26 days. The impellers of hydraulic turbines make one complete revolution in a time equal to 1 second. A helicopter propeller has a period of revolution from 0.15 to 0.3 seconds. The period of blood circulation in humans is approximately 21-22 seconds.

Account: The movement of a body in a circle can be characterized by another quantity - the number of revolutions per unit of time. They call her frequency circulation: ν= 1/T. Frequency unit: s -1 = Hz. ( Write down the definition, unit and formula)(slide)

How to find the frequency if the body makes N revolutions in time t (formula)

Teacher: What conclusion can be drawn about the relationship between these quantities? (period and frequency are reciprocals)

Message3 The crankshafts of tractor engines have a rotational speed of 60 to 100 revolutions per second. The gas turbine rotor rotates at a frequency of 200 to 300 rpm. Bullet. Departing from a Kalashnikov assault rifle, rotates at a frequency of 3000 rpm. To measure the frequency, there are devices, the so-called circles for measuring frequency, based on optical illusions. On such a circle, black stripes are applied and there are frequencies. When such a circle rotates, the black stripes form a circle at the frequency corresponding to this circle. Tachometers are also used to measure frequency. (slide)

Connection Rotation speed and rotation period

ℓ - circumference

ℓ=2πr V=2πr/T

Additional characteristics of movement in a circle. (slide)

Account: Recall what quantities characterize rectilinear motion?

Movement, speed, acceleration.

Account: by analogy, movement in a circle - the same quantities - angular displacement, angular velocity and angular acceleration.

Angular Move: (slide) This is the angle between two radii. Designated - Measured in rad. or deg.

Account: Recall from the algebra course how a radian is related to a degree?

2pi rad.=360 deg. Pi \u003d 3.14, then 1 rad. \u003d 360 / 6.28 \u003d 57 degrees.

Angular speed w=

Angular velocity unit - rad/s

Teacher:. Think about what the angular velocity will be equal to if the body has made one complete revolution?

Student. Since the body has made a complete revolution, the time of its movement is equal to the period, and the angular displacement is 360 ° or 2. Therefore, the angular velocity is.

Teacher: So what did we talk about today? (about curvilinear motion)

5. Questions for consolidation.

What movement is called curvilinear?

Which movement is a special case of curvilinear movement?

What is the direction of the instantaneous velocity in curvilinear motion?

Why is acceleration called centripetal?

What is period and frequency? What units are measured in?

How are these quantities related?

How can curvilinear motion be described?

What is the direction of acceleration of a body moving in a circle with a constant modulo speed?

6.Experimental work

Measure the period and frequency of a body suspended on a thread and rotating in a horizontal plane.

(on the desks you have bodies suspended on threads, a stopwatch. Rotate the body in a horizontal plane evenly and measure the time of 10 full rotations. Calculate the period and frequency)

7. Fixing. Problem solving. (slide)

A.S. Pushkin. "Ruslan and Ludmila"

By the seaside, the oak is green,

golden chain on the oak

And day and night the cat is a scientist

Everything goes around in circles.

Q: What is the name of this movement of the cat? Determine the frequency and period and angular velocity if in 2 min. He does 12 circles. (answer: 0.1 1/s, T=10s, w=0.628rad/s)

P.P. Ershov "Humpbacked Horse"

Well, this is how our Ivan rides

Behind the ring on the okian

The hunchback flies like the wind

And an initiative for the first evening

A hundred thousand miles waved

And he didn't rest anywhere.

Q: How many times did the Humpbacked Horse circumnavigate the Earth during the first evening? The earth has the shape of a ball, and one verst is approximately 1066 m. (Answer: 2.5 times)

8. Test Checking the assimilation of new material(tests on paper)

Test 1

1. An example of curvilinear motion are ...

a) falling stone
b) turning the car to the right;
c) sprinter's run at 100 meters.

2. The minute hand of the clock makes one complete revolution. What is the circulation period?

a) 60 s; b) 1/3600 s; c) 3600 s.

3. A bicycle wheel makes one revolution in 4 s. Determine the rotational speed.

a) 0.25 1/s; b) 4 1/s; c) 2 1/s.

4. The screw of a motor boat makes 25 revolutions in 1 s. What is the angular velocity of the screw?

a) 25 rad/s; b) /25 rad/s; c) 50 rad/s.

5. Determine the rotational speed of the drill of an electric drill if its angular velocity is 400 .

a) 800 1/s; b) 400 1/s; c) 200 1/s.

Answers: b; in; but; in; in.

Test 2

1. An example of curvilinear motion is…

a) the movement of the elevator;
b) a skier's jump from a springboard;
c) the fall of a cone from the lower branch of a spruce in calm weather.

The second hand of the clock makes one full revolution. What is its frequency of circulation?

a) 1/60 s; b) 60 s; c) 1 s.

3. The wheel of the car makes 20 revolutions in 10 seconds. Determine the period of rotation of the wheel?

a) 5 s; b) 10 s; c) 0.5 s.

4. The rotor of a powerful steam turbine makes 50 revolutions in 1 s. Calculate the angular velocity.

a) 50 rad/s; b)/50 rad/s; c) 10 rad/s.

5. Determine the period of revolution of the bicycle sprocket if the angular velocity is equal.

a) 1 s; b) 2 s; c) 0.5 s.

Answers: b; but; in; in; b.

Self test

9. Reflection.

Let's complete it together ZUH mechanism (I know, I learned, I want to know)

10.Summing up, grades for the lesson

11. Homework paragraphs 18,19,

home study: calculate, if possible, all the characteristics of any rotating body (bike wheel, clock minute hand)

Ya. I. Perelman. Entertaining physics. Book. 1 and 2 - M.: Nauka, 1979.

S. A. Tikhomirova. Didactic material in physics. Physics in fiction. 7 - 11 grades. – M.: Enlightenment. 1996.

Topic: Curvilinear motion. Uniform motion of a material point along a circle.

The objectives of the lesson: the formation of students' ideas about curvilinear motion, frequency, angular displacement, period. To acquaint with the formulas for finding these quantities and units of measurement.

Tasks:

educational : to give students an idea of the curvilinear movement of its trajectory, the quantities characterizing it, the units of measurement of these quantities and the formulas for calculation.
Educational : continue the formation of skills to apply theoretical knowledge to solve practical problems, develop interest in the subject and logical thinking.
Educational : continue to develop the horizons of students; the ability to keep notes in notebooks, to observe, to notice the patterns of phenomena, to argue their conclusions.

Lesson type: combined

Methods Keywords: visual, verbal, elements of critical thinking, demonstration experiment.

Equipment: an inclined chute, a ball, a ball on a thread, a toy car, a spinning top, a clock model with arrows, a multimedia projector, a presentation.

DURING THE CLASSES

Psychological mood.

Checking homework.

Frontal survey pp. 24-25 Questions for self-control.

Verification of the decision house. tasks Exercise 5 (2,3)

3. Challenge.

– What types of movement do you know?

How is body movement different from each other?
What is the difference between rectilinear and curvilinear movements?
– In what frame of reference can we talk about these types of motion?
– Compare toolpath and path for rectilinear and curvilinear motions.

2. Explanation of new material combined with demonstration experiment and conversation.

Teacher. Demonstration: a ball falling vertically, rolling down a chute, spinning a ball on a thread, moving a toy car on a table, falling a tennis ball thrown at an angle to the horizon.

Teacher. What is the difference between the trajectories of motion of the proposed bodies? (Student answers)
Try to give yourself definitions curvilinear and rectilinear movements. (Entry in notebooks):
– rectilinear movement – movement along a straight trajectory, and the direction of the force and velocity vectors are the same ;

– curvilinear motion - motion along an indirect path.

Consider two examples of curvilinear motion: along a broken line and along a curve

Teacher. How do these trajectories differ?

Student. In the first case, the trajectory can be divided into straight sections and each section can be considered separately. In the second case, you can split the curve into arcs of circles and straight sections. Thus, this movement can be considered as a sequence of movements occurring along arcs of circles of different radii

Teacher. Give examples of rectilinear and curvilinear motion that you have encountered in your life.

Teacher. Movement in a circle is often characterized not by the speed of movement, but by the time interval during which the body makes one complete revolution. This value is called circulation period and is denoted by the letter T. (Write down the definition of the period).

Student message. A period is a value that occurs frequently enough in nature and technology. Yes, we know. That the Earth rotates on its axis and the average period of rotation is 24 hours. The complete revolution of the Earth around the Sun takes about 365.26 days. The impellers of hydraulic turbines make one complete revolution in a time equal to 1 second. A helicopter propeller has a period of revolution from 0.15 to 0.3 seconds. The period of blood circulation in humans is approximately 21-22 seconds.

Teacher. The movement of a body in a circle can be characterized by another quantity - the number of revolutions per unit of time. They call her frequency circulation: ν = 1/T. Frequency unit: s –1 = Hz. ( Write down the definition, unit and formula)

Student message. The crankshafts of tractor engines have a rotational speed of 60 to 100 revolutions per second. The gas turbine rotor rotates at a frequency of 200 to 300 rpm. A bullet fired from a Kalashnikov assault rifle rotates at a frequency of 3000 rpm.
To measure the frequency, there are devices, the so-called circles for measuring frequency, based on optical illusions. On such a circle, black stripes are applied and there are frequencies. When such a circle rotates, the black stripes form a circle at the frequency corresponding to this circle. Tachometers are also used to measure frequency. .

Work on compiling a conceptual table using§7

Period of circulation

T = 1/v

T = t/n

the time it takes for a body to complete one revolution

Frequency of circulation

s –1 = Hz.

v = 1/T

ν = n/t

number of revolutions per unit time

Cyclic frequency

rad/s

= 2v

= 2/T

4. Consolidation of the material Teacher. In this lesson, we got acquainted with the description of curvilinear motion, with new concepts and quantities. Reply to me next questions:
How can curvilinear motion be described?
What is angular displacement? In what units is it measured?
What is period and frequency? How are these quantities related? In what units are they measured? How can they be identified?

6. Control and self-check

Teacher. The next task is to check how you learned the new material. Testing.

1. An example of curvilinear motion are ...

a) falling stone
b) turning the car to the right;
c) sprinter's run at 100 meters.

2. The minute hand of the clock makes one complete revolution. What is the circulation period?

a) 60 s; b) 1/3600 s; c) 3600 s.

3. A bicycle wheel makes one revolution in 4 s. Determine the rotational speed.

a) 0.25 1/s; b) 4 1/s; c) 2 1/s.

Test 2

1. An example of curvilinear motion is…

a) the movement of the elevator;
b) a skier's jump from a springboard;
c) the fall of a cone from the lower branch of a spruce in calm weather.

2. The second hand of the clock makes one complete revolution. What is its frequency of circulation?

a) 1/60 s; b) 60 s; c) 1 s.

3. The wheel of the car makes 20 revolutions in 10 seconds. Determine the period of rotation of the wheel?

a) 5 s; b) 10 s; c) 0.5 s.

Answers to test 1: b; in; but; in; in
Answers to test 2: b; but; in; in; b

7. Homework: § 7, make tasks to determine the period and frequency of circulation.

8. Summing up. Assessment by self-control cards

No. p / p

Task types

grade

Solving home problems

Drawing up a conceptual table

testing

final grade

9. Reflection

"Self-assessment sheet".

Learned something new

I got upset got joy

Surprised Didn't understand anything

Today we will continue to study movement. We have considered cases when the bodies moved only in a straight line, that is, in a straight line. But how often do we encounter such a movement in life? Of course not. Bodies usually move along curvilinear paths. The movement of planets, trains, animals - all this will be an example of curvilinear movement. It is more difficult to describe such a movement. Change of coordinates will occur in at least two axes, for example OX and OY. Let's compare how the velocity and displacement vectors are directed in rectilinear and curvilinear motion. When a body moves in a straight line, the direction of the velocity vector and the displacement vector always coincide. In order to answer the same question in the case of curvilinear motion, consider the figure. Let us assume that the body moves from point M1 to point M2 along an arc. The path is the length of the arc, the displacement is the M1M2 vector. In geometry, such a segment is called a chord. We see that the direction of speed and displacement do not coincide. With curvilinear motion, we will talk about instantaneous speed. The instantaneous velocity of the body at each point of the curvilinear trajectory is directed tangentially to the trajectory at that point. You can verify this by watching the spray from under the wheels of the car, they also fly out tangentially to the circumference of the wheel. Please note that the speed has a different direction at each point of the curvilinear trajectory, therefore, even if the modulus of the speed remains the same, if the direction of movement has changed, then a new vector must be considered. From the fact that the speed is constantly changing, it follows that the acceleration will also change. Therefore, curvilinear motion is motion with acceleration. Suppose a body moves along some curvilinear trajectory. There can be an infinite number of such trajectories, is it really necessary to describe their own laws of motion for each of them? It turns out that the individual parts of the trajectory can be approximately represented as arcs of circles. And the curvilinear movement itself, in most cases, can be represented as a set of movements along arcs of circles of various radii. By studying circular motion, we will be able to describe more complex cases of motion. Remember, if the speed of the body and the force acting on it are directed along one straight line, then the body moves rectilinearly, and if they are directed along intersecting lines, then the body moves curvilinearly. Determine the trajectory along which the stone rotating on the thread will fly if the thread suddenly breaks? The instantaneous speed of the stone is directed tangentially to the curvilinear line, therefore, at the moment of breakage, according to the law of inertia, the body will move, maintaining the same speed, that is, along the same tangent. The truck is moving along a curved path. The modulo speed is a constant value. Can we say that the acceleration of the truck is zero? It is impossible to state that the acceleration of the truck is equal to zero, since the speed has a different direction at each point of the curvilinear trajectory, therefore, even if the speed modulus remains the same, a new vector must be considered. From the fact that the speed is constantly changing, it follows that the acceleration will also change. We already know that force is the cause of acceleration. Indicate on which sections of the curvilinear motion the force acted?
Justify the answer. On the trajectory marks of the position of the body are made at regular intervals. The force acted in the area 0-3. The body moved in a straight line, but the speed of the body changed (the body moved at an accelerated rate), that is, under the action of a force. The force acted in the area 7-8. The magnitude of the speed did not change, but the direction changed (the body moved at an accelerated rate), that is, under the action of a force.

Scenario lesson number 26

Lesson topic: Rectilinear and curvilinear motion. The movement of a body in a circle with a constant modulo speed.

Subject: physics

Teacher: Apasova N.I.

Grade: 9

Textbook: Physics. Grade 9: textbook / A. V. Peryshkin, E. M. Gutnik. - 3rd ed., stereotype. - M .: Bustard, 2016

Lesson type: lesson in discovering new knowledge

Lesson Objectives:

To create conditions for the formation of students' ideas about the curvilinear movement, the quantities that characterize it;

Promote the development of observation logical thinking;

Contribute to the formation of a scientific worldview and interest in physics.

Lesson objectives:

- give examples of rectilinear and curvilinear motion of bodies; name the conditions under which bodies move rectilinearly and curvilinearly; calculate the module of centripetal acceleration; depict in the figures the vectors of velocity and centripetal acceleration when the body moves in a circle; explain the cause of centripetal acceleration during uniform motion in a circle (subject result);

- master the skills of independent acquisition of new knowledge about the movement of the body in a circle; apply heuristic methods in solving the problem of the cause of centripetal acceleration in case of uniform motion in a circle; master regulatory UUD in solving computational and qualitative problems; develop monologue and dialogic speech (metasubject result);

To form a cognitive interest in species mechanical movement; develop Creative skills and practical skills in solving qualitative and computational problems for the uniform movement of a point along a circle; be able to accept independent solutions, justify and evaluate the results of their actions (personal result).

Teaching aids: textbook, collection of tasks; computer, multimedia projector, presentation "Rectilinear and curvilinear motion"; inclined chute, ball, ball on a thread, toy car, spinning top.

I. Organizational moment (motivation to learning activities)

The purpose of the stage: the inclusion of students in activities at a personally significant level

Greeting, checking readiness for the lesson, emotional mood.

"We are truly free when we have retained the ability to reason for ourselves." Cicero.

Listen, tune in to the lesson.

Personal: attention, respect for others

Communicative: planning educational cooperation

Regulatory: self-regulation

II. Knowledge update

The purpose of the stage: repetition of the studied material necessary for the "discovery of new knowledge", and the identification of difficulties in the individual activity of each student

Organizes mutual checking of homework and a conversation on control questions

1. Formulate the law of universal gravitation. Write down the formula.

2. Is it true that the attraction to the Earth is one of the examples of universal gravitation?

3. How does the force of gravity acting on a body change as it moves away from the Earth?

4. By what formula can one calculate the force of gravity acting on a body if it is at a small height on the Earth?

5. In which case will the force of gravity acting on the same body be greater: if this body is located in the equatorial region the globe Or one of the poles? Why?

6. What do you know about free fall acceleration on the Moon?

No. 2,3 - orally

No. 4 - at the board

We know that all bodies are attracted to each other. In particular, the Moon, for example, is attracted to the Earth. But the question arises: if the Moon is attracted to the Earth, why does it revolve around it, and not fall to the Earth?

In order to answer this question, it is necessary to consider the types of motion of bodies.

What types of movements have we studied?

What is called uniform motion?

What is the speed of uniform motion?

What movement is called uniformly accelerated?

What is body acceleration?

What is movement? What is a trajectory?

Answer questions

Mutual check of the task

Answer questions

Cognitive: logical reasoning; consciously and voluntarily build a speech statement in oral form

Regulatory: the ability to listen in accordance with the target setting; clarification and addition of students' statements

II a. Setting goals and objectives for the lesson.

Purpose of the stage: creation of a problem situation; fixing a new learning task

Formulation of the problem.

Demonstration of experience: spinning the top, spinning the ball on the thread

How can you characterize their movements? What do their movements have in common?

So, our task in today's lesson is to introduce the concept of rectilinear and curvilinear motion. Body movements in a circle. slide 1

To set goals, I propose to analyze the scheme of mechanical movement. Slide 2.

What are the goals for our topic? slide 3

speculate

Write down the topic of the lesson, formulate goals

Regulatory: regulation of educational activities; ability to listen in accordance with the target setting

Personal: readiness and ability for self-development.

I V. Problematic explanation of new knowledge

The purpose of the stage: ensuring the perception, comprehension and primary consolidation by students of knowledge about curvilinear motion, quantities characterizing it

Explanation of new material with a presentation, demonstration of experiments, organization independent work students with textbook

Demonstration: a ball falling vertically, rolling down a chute, spinning a ball on a thread, moving a toy car on a table, falling a ball thrown at an angle to the horizon.

What is the difference between the movements of the proposed bodies?

Try to give yourselfdefinitions curvilinear and rectilinear movements.
– rectilinear movement – movement along a straight path
– curvilinear movement – movement along an indirect trajectory.

Task 1. Identify the main features of rectilinear and curvilinear motion

1. Read § 17

2. Based on fig. 34 p. 70 write down in a notebook the signs that a moving body has:

a) rectilinearly (1 b)

b) curvilinear (1 b)

3. Choose the correct statement: (2 b)

A: if the force vector and the velocity vector are directed along the same straight line, then the body moves in a straight line

B: if the force vector and the velocity vector are directed along intersecting lines, then the body moves curvilinearly

1) only A 2) only B 3) both A and B 4) neither A nor B

Do output what determines the type of trajectory.

The action of a force on a body in some cases can only lead to a change in the modulus of the velocity vector of this body, and in others to a change in the direction of the velocity.

Consider two examples of curvilinear motion: along a broken line and along a curve. Slides 7.8

How are these trajectories different?

Task 2. Represent movement along any curvilinear trajectory as movement along a circle.

1. Consider fig. 35 p. 71, analyze it based on the text of the textbook.

2. Draw your own curvilinear trajectory and represent it as a set of arcs of circles of different radii. (1 b)

That. this movement can be considered as a sequence of movements occurring along the arcs of circles of different radii. Slide 9

Task 3. Determine how the linear velocity vector is directed when moving in a circle.

1. Read § 18 page 72.

2. Draw the velocity vector at points B and C in your notebook and draw a conclusion. (2b)

Give examples of curvilinear motion that you have encountered in your life.

Planets and artificial satellites of the Earth move along curvilinear trajectories in outer space, and on Earth all kinds of means of transport, parts of machines and mechanisms, river waters, atmospheric air, etc. slide 10.

If you press the end of a steel rod against a rotating grindstone, then the hot particles coming off the stone will be visible in the form of sparks. These particles fly at the same speed that they had at the moment of separation from the stone. It is clearly seen that the direction of movement of the sparks coincides with the tangent to the circle at the point where the rod touches the stone.Tangent moving spray from the wheels of a skidding car.

Thus, the instantaneous velocity of the body at different points of the curvilinear trajectory has a different direction, and note that the velocity and force vectors acting on the body are directed along intersecting straight lines. Slide 11.

Modulo, the speed can be the same everywhere or change from point to point. But even if the modulus of speed does not change, it cannot be considered constant. Speed is a vector quantity. And timesvelocity vector changes , so there is an acceleration. Therefore, curvilinear motion is alwaysacceleration , even if modulo the speed is constant.(Slide 12).

Task 4. Study p concept of centripetal acceleration.

Answer the questions:

2) Where is the acceleration of the body directed when moving along a circle with a constant modulo speed? (1 b)

3) What formula can be used to calculate the modulus of the centripetal acceleration vector? (1 b)

4) What formula is used to calculate the module of the force vector, under the influence of which the body moves in a circle with a constant speed in absolute value? (1 b)

Acceleration of a body moving uniformly in a circle at any pointcentripetal , those. directed along the radius of the circle towards its center. At any point, the acceleration vector is perpendicular to the velocity vector. slide 13
Centripetal acceleration module: a c \u003d V 2 /R where V is the linear velocity of the body, and R is the radius of the circle. Slide 14

From the formula it can be seen that at the same speed, the smaller the radius of the circle, the greater the centripetal force. So, at the corners of the road, a moving body (train, car, bicycle) should act towards the center of curvature, the greater the force, the steeper the turn, i.e., the smaller the radius of curvature.

According to Newton's second law, acceleration is always co-directed with the force, as a result of which it arises. This is also true for centripetal acceleration.

How is the force directed at each point of the trajectory?

This force is called centripetal.

The centripetal force depends on the linear speed: with increasing speed, it increases. It is well known to all skaters, skiers and cyclists: the faster you move, the harder it is to make a turn. Drivers know very well how dangerous it is to turn a car sharply at high speed.

The centripetal force is created by all the forces of nature.

Give examples of the action of centripetal forces by their nature:

elastic force (stone on a rope);

gravity (planets around the sun);

friction force (turning).

Watching the demonstration

They answer the question: according to the type of trajectory, these movements can be divided into movements along a straight line and along a curved line.

They give definitions. slide 4

Carry out the task

Draw a conclusion

Slides 5,6

Answer the question: in the first case, the trajectory can be divided into straight sections and each section can be considered separately. In the second case, you can split the curve into arcs of circles and straight sections

Working with textbook

Carry out the task

Working with textbook

Give examples

Working with textbook

Write down the formula

Answer the question

Write the formula in a notebook

Give examples

Cognitive: highlighting essential information; logical reasoning; consciously and voluntarily build a speech statement in oral form; the ability to formulate questions; paragraph content analysis.

Communicative: listening to the teacher and comrades, building clear statements for the interlocutor.

Regulatory: the ability to listen in accordance with the target setting; plan your actions; clarification and addition of students' statements

V. Primary test of understanding

The purpose of the stage: pronunciation and consolidation of new knowledge; identify gaps in the primary comprehension of the studied material, misconceptions of students; make a correction

Problem solving

1. Solving quality problems

No. 1624-1629(P)

2. Solution of calculation problems

Working in pairs

Participate in a group discussion of problem solving

Regulatory: planning your activities to solve the problem, self-regulation

Personal: self-determination with the aim of obtaining the highest score

V аΙΙ. The result of the lesson (reflection of activity)

The purpose of the stage: students' awareness of their educational activities, self-assessment of the results of their activities and the whole class

The teacher asks the students to generalize the acquired knowledge in the lesson. Calculate the number of points for correctly completed tasks and give yourself a grade.

21 -19 points - score "5"

18-15 points - score "4"

14-10 points - score "3"

Offers to return to the goals and objectives of the lesson, analyze their implementation

Have all goals been met?

What have you learned?

I did not know…

Now I know…

Students enter into a dialogue with the teacher, express their opinion, summarize the lesson

Cognitive: the ability to draw conclusions.

Communicative: to be able to formulate own opinion and position.

Regulatory: the ability to exercise self-control and self-esteem; adequately perceive the teacher's assessment