Teaching plan 1 of physics teaching in senior high school
Teaching objectives
Knowledge target
1, knowing the conditions;
2. Being able to judge the existence, size and direction of stillness according to the motion state of objects in simple problems; Know that there is maximum silence;
3, master the dynamic friction coefficient, calculate the slip in specific problems, and master the method of judging the direction;
4. Know the factors that affect the dynamic friction coefficient;
capability goal
1. Summarize the conditions and characteristics through observation and demonstration experiments, and cultivate students' observation and generalization ability. By comparing the difference between static and slippery, students' comprehensive analysis ability is cultivated.
Affective goal
Infiltrate the education of physical methods. When analyzing the object, highlight the main contradiction, ignore the secondary factors and irrelevant factors, and summarize the conditions and laws.
Teaching suggestion
I. Basic knowledge and skills:
1, when two objects are in contact with each other, relative sliding motion will hinder the relative motion on their contact surfaces, which is called sliding;
2. When two objects are in contact with each other and have a tendency to slide relatively, but remain in a relatively static state, the force that hinders the relative sliding appears on their contact surfaces.
3. The sliding between two objects is directly proportional to the pressure between the contact surfaces of these two objects.
4. The coefficient of dynamic friction is related to the materials of two objects in contact with each other.
5. The direction is tangent to the contact surface, which is opposite to the relative motion or relative motion trend of the object.
6. Maximum static existence-maximum static.
Second, the key and difficult analysis:
1, the content of this lesson is divided into two parts: sliding and static. The emphasis is on the conditions, characteristics and laws of production, and the relationship is obtained through demonstration experiments.
2. The difficulty is that when understanding the sliding formula, especially when understanding the moving object on the horizontal plane, students often take gravity as pressure without analyzing the specific situation.
Teaching suggestion
First, explain the related concepts of teaching methods and suggestions
Based on the basic facts, this paper introduces the existence of sliding time and static time, and makes students accept this existence by using the knowledge of the balance of two forces. Because the content is the difficulty of this section, it is not required to explain it in one step, and its concept can be understood through experiments and student discussions.
1, let students find examples used in life and production;
2, let students think and discuss, such as:
1, it must be resistance;
2. Static objects must be static;
3. The moving object cannot be static;
It is mainly emphasized that the contact force hinders the relative motion or the trend of relative motion between objects, but it does not necessarily hinder the motion of objects, that is, it can also play the role of driving force in motion, such as the example of conveyor belt.
Second, the size of the explanation and what factors are related to the teaching suggestions.
1, the sliding size is related to the material of the object and the smoothness of its surface; Related to the positive pressure between objects; But has nothing to do with the size of the contact area. Pay attention to the explanation of positive pressure.
2. The size of sliding can be expressed by a formula: the relationship between the dynamic friction coefficient and the surfaces of two objects is not that the brighter the surfaces, the smaller the sliding friction coefficient is. In fact, when the surfaces of two objects are rough, the dynamic friction coefficient will be large because of the staggered teeth on the contact surface; For very smooth surfaces, especially very clean surfaces, molecular forces play a major role, so the dynamic friction coefficient is larger, and the smoother the surface, the greater the dynamic friction coefficient. However, in mechanics, it is often called "the surface of an object is smooth", which is an expression that ignores the object. In fact, it is an idealized model and has nothing to do with the above description.
3. The coefficient of dynamic friction is a unitless physical quantity, which can directly affect the motion state and force of an object.
4. The magnitude of static electricity increases with the increase of external force, which is equal to the magnitude of external force. However, the static state cannot increase indefinitely, but has a maximum value. When the external force exceeds this maximum, the maximum static force is called the maximum static force. Experiments show that the maximum static force is determined by the formula, which is called the static friction coefficient, that is, the positive pressure on the object. The relationship between size and external force is shown in the figure: the size of sliding.
High school physics teaching plan II
learning target
1. Deeply understand the conditions of elasticity, accurately judge the direction of elasticity, memorize Hooke's law, and improve the ability to analyze elasticity problems.
2. Self-study, cooperative exploration, and learn to use the hypothesis method to judge whether there is flexibility.
3.*** Input, recognizing that physics is closely related to production and life.
Important and difficult
Key points: the judgment of the condition and direction of elasticity, Hooke's law;
Difficulties: judge whether there is elasticity or not, and judge the direction of elasticity.
explain
1. Read through the textbook P54-P56 first, outline the basic concepts in this section, and make clear the conditions and directions of elasticity and Hooke's law.
2. On the basis of understanding the content of the textbook, independently complete the tutorial plan, and do not make requirements when consolidating the training preview.
3. Write carefully, find out problems and doubts, and prepare for class discussion and questioning.
Problem guidance
1. What is deformation and what is elastic deformation?
2. What is flexibility?
3. Write your understanding of Hooke's law and stiffness coefficient.
Cooperative investigation
Exploration point 1: elastic deformation and elasticity
Question 1. When the spring is stretched or compressed, plasticine can be kneaded into various models. What's the difference between these two deformations?
Question 2. In the picture below, the ball and the ball are at rest. Analyze whether there is elastic force between two balls in four cases.
According to the above situation, the conditions of elastic force generation and the methods of judging whether there is elastic force are summarized.
Used for training
1. The following statement is correct.
A. hard objects shall not be deformed.
B. press the table hard. Although invisible to the naked eye, the desktop must be deformed.
C. When two objects touch each other, an interactive elastic force will be generated.
D. there is elasticity between two objects, and the objects do not necessarily deform.
2. Elastic deformation is
A. the pole deformation of pole vaulters when they take off.
B. When you sit in a chair, the chair surface will be slightly deformed.
C. the aluminum bucket was smashed flat.
D. the spring is forcibly straightened.
Explore the second point, several kinds of elasticity and their direction.
Question 3. As shown in the figure, a building block is still on a horizontal desktop, draw a schematic diagram of the elasticity of the building block and the desktop, and analyze the reasons why the building block exerts elasticity on the desktop.
Question 4. As the picture shows, a small ball is hung from the ceiling with a string. 1 Analyze the force on the ball and draw the schematic diagram of each force.
The tension of the rope on the ball is also elastic. What is its direction law?
Used for training
3. A small piece of wood is put on the table. The following statement is correct.
A. At the contact point, only the table is acted by elasticity, and the wood block is not acted by elasticity.
B. Both the desktop and the small wooden block are subjected to elastic force at the contact point.
C. The pressure of wood blocks on the desktop is the force exerted on the desktop to restore the original state after the wood blocks are deformed.
D. the pressure of the block on the table is the gravity of the block.
Please draw the elastic force on the rod or ball in the picture.
A.this pillar leans against the wall.
B. put the rod into the hemispherical groove.
C. the ball is hung on the vertical wall with thin lines.
Point d 1 is the center of gravity of the ball, point 2 is the center of the ball, and point 1 and point 2 are on the same vertical line.
Explore the third point, Hooke's law
[Experiment]: The hook code is attached to a spring with a length scale behind it. When the number of hook codes increases, the elasticity in the spring increases and the elongation of the spring increases. What does this experiment show?
Question 5. Briefly describe the content of Hooke's law and write the formula.
Question 6. We define it as the stiffness coefficient of the spring. Please write down its symbol and unit.
For training:
5. The natural length of a light spring is 15cm, and the length becomes 18cm after hanging a weight of 0.5kg below. Find the stiffness coefficient of the spring.
Consolidation training
1. Regarding the direction of elasticity, the following statement is correct.
The direction of pressure is always perpendicular to the contact surface and points to the pressed object.
B the direction of supporting force is always perpendicular to the supporting surface and points to the supported object.
C the direction of the rope tension on the object may not be along the direction of the rope.
D The direction in which the rope pulls the object always points to the direction in which the rope shrinks along the rope.
2. When the book is placed on the table, it will be affected by the elasticity of the table. The direct cause of this elasticity is
A. book deformation B. desktop deformation C. gravity on the book D. gravity on the desktop
3. A car is parked on the horizontal plane. The following statement is correct.
A. Due to the elastic deformation of the ground, the ground is subjected to downward elastic force; The car has no elastic deformation, so it has no elasticity.
B. Due to the elastic deformation of the ground, the ground is subjected to downward elastic force; The car received an upward elastic force because it was also deformed.
C. the upward elasticity of the car is due to the deformation of the ground; The downward elasticity of the ground is due to the elastic deformation of the car.
D. The car is subjected to upward elastic force, and the force applying object is the ground; The ground is subjected to downward elastic force, and the force applying object is a car.
4. As shown in the figure, the relationship between the length L of the light spring and the elastic force is determined by the chart:
1 original length of spring;
2. Stiffness coefficient of the spring;
3 when the spring length is 0.20m, the size of the elastic force.
Teaching plan 3 of physics teaching in senior high school
Teaching objectives
Knowledge and skills: understand the relationship between the speed of uniform variable speed linear motion and time and acceleration, and calculate the speed of uniform variable speed motion; Understand the meaning of speed image of uniform and variable speed movement; Knowing the relationship between the displacement of uniform variable speed motion and time and acceleration will calculate the displacement of uniform variable speed linear motion.
Process and method: By establishing velocity formula and displacement formula, experience the role of physical theory in physical research, and experience the methods and ideas of deducing new theories by using known theories; Through the establishment of velocity image, the function of image method in physics research is realized.
Emotion, attitude and values: through the expression of the same law by physical formulas and images, we can experience the diversity of the expression forms of physical laws, appreciate the formal beauty of physical laws, and cultivate students' aesthetic consciousness.
Teaching focus
Velocity formula, velocity image, displacement formula.
Teaching difficulties
Significance and application of velocity image.
training/teaching aid
Ppt courseware
teaching process
◆ Create a situation-lead to a topic.
1. Review questions:
1 What is uniform linear motion? What are the characteristics of its speed? What are the characteristics of acceleration?
How to calculate the acceleration of uniform linear motion? The acceleration of the uniform acceleration linear motion of the object is 2m/s2, which shows how the speed of the object changes.
2. Summary of assessment:
1 uniform linear motion. The speed direction is unchanged, and the size changes evenly with time. The acceleration is neither zero nor constant.
The calculation formula of acceleration is: refers to the speed at which an object increases or decreases by 2m/s per second.
3. Ask the question: If the initial velocity and acceleration at the beginning of the movement are known, how to calculate the final velocity at a certain moment?
◆ Cooperative inquiry-new lesson learning
First, the speed of linear motion with uniform speed change.
1. Research on the problem: 10 The calculation speed problem in the textbook "Speed of Uniform Linear Motion".
2. Derivation of the velocity formula of uniform linear motion.
1 Derived from the Meaning of Acceleration ── A Case Study
Example: 1 The velocity of the particle at time 0 is vom/s, and the linear motion is uniformly accelerated with the acceleration am/s2 from time 0 to find the velocity of the particle at the end of ts.
Analysis: the velocity of particle 0 at a certain moment is VOM/s; According to the meaning of acceleration, the speed of particle increase in 1s is: am/s; The increasing speed in the ts time from time 0 to the end of ts is ATM/s; The speed at the end of ts should be the sum of the speed at time 0 and the increased speed in ts time, namely:.
2 Derived from the definition of acceleration:
The definition of acceleration is: you can get it by removing the denominator and moving the term:
3. Exchange assessment-summary
1 The speed formula of uniform linear motion is:, and if the particle moves in a uniform linear motion from rest, there are:
2 Significance of the formula: The formula reflects the relationship between the speed of uniform linear motion and the change of time, involving four physical quantities related to motion. If three of them are known, we can use this formula to find another unknown physical quantity.
3 Direction of each quantity in the formula: The four physical quantities in the formula are all vectors except time, with both magnitude and direction. Because of the linear motion, the directions of the three vectors are all on the same straight line. Therefore, it can be determined in advance that the direction of a certain quantity is positive, and when other quantities with the same direction are substituted into the formula, it is "positive+",otherwise it is "negative-"; A calculated quantity is positive, which means that its direction is consistent with the selected positive direction; Negative means that its direction is opposite to the selected positive direction. In this way, using the formula, we can not only calculate the size of the unknown quantity, but also calculate its direction.
When using the speed formula, the initial speed direction is generally selected as the positive direction.
◆ Case Study-Summary and Integration
Example 2 textbook "Example 2" on page 1 1.
A. Case study
B note: when using the formula, the units of each quantity should be converted into international units; Taking the initial velocity direction as the positive direction, the initial velocity is positive; When accelerating uniformly, the acceleration is positive, and when decelerating uniformly, the acceleration is negative. When its magnitude is substituted into the formula, a "-"sign should be added before its magnitude; The calculated final speed is "+",indicating that the direction is consistent with the initial speed, and the calculated final speed is "-",indicating that the direction is opposite to the initial speed.
C. About the sign of the vector: As mentioned above, the sign of the vector only indicates the direction of the vector, not the size of the vector. When comparing the sizes of two vectors, take their absolute values for comparison.
Second, the speed image of uniform linear motion
1. Cooperative exploration
1 Preparation of mathematical knowledge and methods: In mathematics, in addition to expressing the relationship between one dependent variable and another with functional relationship, you can also express the relationship between the quantity represented by the ordinate axis and the quantity represented by the abscissa with straight lines or curves on the rectangular coordinate plane, such as the direct proportional function and the inverse proportional function that you learned in the beginning.
2 Methods Micro-movement: The formula reflects the relationship between the instantaneous speed of uniform linear motion and time change, just like a math problem, which can also be expressed by images on the coordinate plane. If a plane rectangular coordinate system is established, the horizontal axis represents time and the vertical axis represents the instantaneous speed of each time. According to each time and the corresponding instantaneous velocity in the particle motion, a series of points can be drawn on the coordinate plane, and these points are connected by smooth straight lines or curves. This is the velocity-time image of the particle, referred to as "v-t" image, which vividly represents the velocity change of the particle.
Learn to build a "v-t" image: instruct students to build a "v-t" image with the speed of uniformly accelerated linear motion particles reflected in the table on page 1 1 of the textbook.
A. Draw a plane rectangular coordinate system-"TOV" coordinate system, and determine the coordinate scale; B. Tracking points; C. Contact
2. Exchange assessment
1 Image features: straight line. In the case of uniform acceleration, it is a straight line obliquely upward; In the case of uniform deceleration, it is a straight line obliquely downward. If the initial velocity is zero, it is a straight line passing through the origin; If the initial velocity is not zero, it is a straight line, but the origin.
2 The meaning of image:
A. It means that the speed of linear motion with uniform speed change changes uniformly with time, and the instantaneous speed at a certain moment can be directly read from the image;
B. Express the acceleration of uniform linear motion: randomly select two points from the image and calculate the acceleration. According to the knowledge of analytic geometry, the ratio is the slope of the straight line of the image, that is, the tangent of the included angle between the image and the T axis. The more inclined the image, the greater the absolute value of the slope. Therefore, the slope of the v-t image represents the acceleration.
◆ Case Study-Summary and Integration
Example 3 is a v-t image of three particles in motion. What kind of sports do they represent?
Analysis: The images are all straight lines, indicating that all three particles are moving in a straight line at a uniform speed. The slope of image A is not equal to zero and positive, and the motion represented by image A is uniformly accelerated linear motion. The slope of B image is zero, and the image is parallel to the T axis, which means that the acceleration is zero, and the motion represented by B image is uniform linear motion; The slope of C-image is not equal to zero and negative, and the motion represented by C-image is linear motion with uniform deceleration.
Third, the displacement of uniform linear motion
1. Cooperative exploration
1 average speed of uniform linear motion;
Let the initial velocity and final velocity of uniformly variable linear motion particles in time t be vo and vt respectively, then the average velocity during this time is:
Note: This formula is only applicable to uniform linear motion, which is derived from the definition of average velocity and the characteristics of uniform linear motion.
2 Derivation of displacement formula:
Substitution, substitution; The displacement formula of uniform linear motion is obtained.
Discussion on the formula: the formula represents the relationship between displacement and time of uniform linear motion, involving five physical quantities, of which four are known and unknown can be calculated; When this formula is applied, the initial velocity direction is generally positive. Therefore, when a particle moves in a straight line with uniform acceleration, the substitution acceleration is positive, and it is negative when it moves in a straight line with uniform deceleration. If the initial velocity of a particle is zero, that is, the particle accelerates at a constant speed from rest, then:
2. Case Study-Summary and Integration
Example 4 textbook page 1 1 Example 3
1 analysis example
It is emphasized that the motion of automobiles and other vehicles after braking is linear motion with uniform deceleration. When the speed drops to zero, the acceleration will become zero, and then it will be known that the car will be at rest and its deceleration will end. Therefore, when solving the displacement of a car after braking for a period of time or the speed at a certain moment, we must first judge the real movement time after braking.
◆ Exchange evaluation-summary and induction
1. Classroom exercise: textbook page 17 "Review and consolidate" 5, 9.
2. Teacher's summary: Look at the blackboard design.
arrange work
1. Review the text and complete the "Review and Consolidation" on page 17 of the textbook in writing.
2. Write a short paper "Velocity-Time Image of Uniform Linear Motion".
Preview this section "Free Fall".
blackboard-writing design