Wen Yi decomposition of force model of teaching plan
Teaching design
The first lesson of "Decomposition of Force"
Xi 'an China Railway High School Duan Caifeng
Postal code: 7 10054
Teaching design of force decomposition (lesson 1)
Duan Caifeng from Xi 'an China Railway School
Textbook analysis
This section is the fifth section of Chapter III of Interaction published by People's Education Publishing House, which is the further understanding and application of the vectoriality of force, the relationship between resultant force and component force, and the parallelogram law of force after the fourth section, and it is a key point of this chapter. The specific contents include: the concept of force decomposition, the law of force decomposition, the method of force decomposition in practical problems, the condition of unique solution, the law of vector addition and so on. It should be divided into two classes, and this instructional design is the first class.
Analysis of learning situation
Students learn the definitions of resultant force and component force, know the relationship between resultant force and component force, understand the parallelogram rule of force synthesis, and use the parallelogram rule to find the magnitude and direction of resultant force. Therefore, the concept of decomposition is not difficult to understand. The decomposition of force is the inverse operation of the composition of force, and it follows the parallelogram rule. However, it is difficult to decompose force in specific problems, especially how to determine the direction of component.
design concept
The content of this lesson is closely related to real life. My design concept is to extract models from production and life, and then move towards production and life. Insisting on taking students as the main body, we created a lot of rich experiments and situations: lifting objects on the platform scale, placing objects on the inclined plane, hanging keys on compasses, placing basketball between the inclined plane and the baffle, etc. , so that students can fully experience and understand the practical role in specific problems and easily break through the difficulties.
Teaching objectives
1, knowledge and skills
(1) The decomposition of understanding is the inverse operation of force composition, which follows the parallelogram rule.
(2) The component direction should be determined according to actual needs.
(3) It will be used as a knowledge component of drawing method and right triangle.
2. Process and method
(1) Further understand "equivalent substitution".
(2) The ability to discover, explore and solve problems through inquiry.
(3) Mastering the ability of applying mathematical knowledge to solve physical problems.
3. Emotional attitudes and values
(1) Enjoy the happiness of success by guessing and exploring.
(2) Feel that physics is around, and have the consciousness of applying physical knowledge to life and production experiments.
Teaching emphases and difficulties
Key points: 1. Correctly judge the function and decomposition of force in specific problems.
2. I will use the parallelogram rule to calculate the component, and I will use the right triangle knowledge to calculate the component.
Difficulties: 1, the equivalent substitution relationship between component force and resultant force.
2. The actual effect of force decomposition.
Ways to break through the key points and difficulties
Stimulate students' interest through story introduction; Make full use of teaching resources, create a large number of rich experiments and situations, and make boring knowledge vivid; Students explore and solve problems in groups, give full play to collective wisdom, show opportunities to students in groups, mobilize their enthusiasm for learning and share their achievements; Combine reality and reap the happiness of success.
Teaching means and methods
Tutoring plan+experimental inquiry experience+cooperative discussion+multimedia.
training/teaching aid
An electronic platform scale, a slider with thin lines, a compass, a bunch of keys, a self-made slope, a self-made slope with a vertical baffle covered with sponge, a slider, a football, a scale and multimedia courseware.
teaching process
Introduction of new lessons (2 minutes)
One day, Xiaoming and his family went for an outing. On the way, they saw a truck accidentally stuck in a mud pit on the side of the road. Many adults push behind, but they can't get it out. At this time, Xiaoming volunteered and said, "I'll try!" " "I saw him find a thick rope and tie one end of it to the car and the other end to the big tree next to it. Then he slowly pulled the car out with a little force in the center of the rope. Everyone was shocked: "Don't you think this is the legendary' four Liang'?"
So, Xiao Ming has studied Kung Fu. Does he have any special skills? After learning the new lesson, we will answer this question again.
Activity design: Teachers tell stories, courseware shows scenarios, and students listen to stories.
Design intention: The story is introduced into the classroom to stimulate students' interest in learning.
(B) the new curriculum teaching
First, check the completion of the tutorial (3 minutes)
Activity design: The teacher asked two students to report the contents of their review plan and preview plan respectively, and the other students corrected their mistakes.
Design intention: Reviewing the relationship between resultant force and component force and the method of force synthesis will help students to deepen their understanding of "equivalent substitution" of resultant force and component force, deepen their understanding of "parallelogram law", and preliminarily understand the concept and law of force decomposition, so as to prepare for the new lesson.
Second, the new curriculum teaching
1, autonomous learning (4 minutes)
Teacher: Through preview, we have made it clear that the decomposition of force is a process of solving the component of force by the known resultant force, and the law of force decomposition is also a parallelogram law, but I still have a few questions: (courseware demonstration problem)
Why is the decomposition of force the inverse operation of the composition of force?
Decomposition of a force with a certain size and direction, if there is no conditional restriction, why can countless components be obtained?
When the directions of two components are known, how many groups of components are obtained? How to draw the map exactly?
Activity design: give students three minutes to read the contents of 64 pages of the textbook with questions and draw pictures if necessary; Ask a student to draw a decomposition diagram of the force when the directions of two components are known on the blackboard. After three minutes, let the students answer the questions in turn, the teacher corrects the mistakes, and the courseware shows the answers and drawing methods, emphasizing the answers to the questions.
Design intention: Answer students' difficult questions, guide students to know what the task of force decomposition is, and know how to draw the method of force decomposition when the two directions of force component are known, so as to lay the foundation for later teaching.
2. Cooperative inquiry (10 minutes)
Teacher: From the above questions, we can imagine that if in a specific problem, we can try to determine the direction of the component of the resultant force, we can get the determined component by using the parallelogram rule, and we can also solve two components by using the triangle knowledge we have learned.
Activity design: students are divided into four groups, equipped with necessary experimental equipment, and are required to complete their tasks within ten minutes. Focus: study Galileo's research ideas: observation-conjecture-experiment-conclusion; The final component of the force should be expressed by the trigonometric function value of the resultant force and the known angle.
Task arrangement and equipment:
The first group: decompose diagonal tension. Provide instruments: electronic platform scale, slider with thin line.
The second group: decompose the gravity of the object on the inclined plane. Provide instruments: inclined plane and slider.
The third group: decompose the force of the object on the triangular bracket. Provide instruments: compasses and weights.
The fourth group: decompose the gravity of the object between the vertical baffle and the inclined plane. The inclined plane is covered with sponge and football with vertical baffle.
Design intention: enjoy the happiness of success through guessing and exploring; Cooperative learning, giving full play to students' dominant position.
3. Group presentation (15 minutes)
Activity design: Each group sent two students to the stage to show them from the aspects of observation, speculation, experimental design, experimental phenomenon, conclusion and resultant decomposition results. Other members of the group can add and ask questions.
Design intention: to cultivate students' awareness of expressing their views and their desire to communicate with others.
4. Classroom test (6 minutes)
Activity design: Teachers and students * * * sum up the three steps to find a force in specific problems:
(1) Determine the direction of two components according to the action of force.
⑵ Make two parts according to the parallelogram rule.
⑶ Calculate the size and direction of the component according to the triangle knowledge.
Students complete two tests on the study plan in 5 minutes. The teacher announced the answer and explained it briefly.
Design intention: Students sum up the methods and steps of solving problems and skillfully solve problems through practice.
Decomposition of force model II
Teaching objectives
Knowledge and skills
1, do you know what is the decomposition of force?
2. Knowing that the decomposition of force also follows the parallelogram law, we can make the decomposition diagram of force.
3, can use the right triangle knowledge to calculate the component size.
4, can analyze and explain some phenomena in production and life, can use the knowledge of force decomposition to solve some simple practical problems.
Process and method
1. Analyze the function of force from the force of an object, so as to determine the direction of component force and cultivate students' ability to analyze and solve problems.
2. Strengthen the thinking method of "equivalent substitution"
Emotional attitudes and values
1. Cultivate students' experimental exploration spirit and scientific rigor through experiments.
2. Cultivate students' cooperative spirit and ability through group cooperation and inquiry.
3. Improve students' interest in physics by connecting with real life.
Teaching focus
Master the decomposition method of force, use the knowledge of right triangle to make the decomposition diagram of force and calculate the component of force.
Key Breakthrough: In both interactive inquiry and independent inquiry, students are arranged to draw and calculate, so that students can master methods and improve their abilities.
Difficult reading in teaching
According to the stress of the problem, determine the direction of the component.
Difficulty breakthrough: through experimental means, turn the invisible into the visible, and turn the feeling into the visible. Through interactive inquiry between teachers and students, group inquiry and independent inquiry, we can deeply understand what force is and how to determine the direction of component according to the function of force!
teaching process
[Introduction to class]
Teacher: I am honored to come to Fuchun Middle School to study with my classmates. First, we invite two boys to come forward and finish a little game with the teacher.
Teacher-student interaction: invite two boys to simulate tug-of-war and enter the stalemate stage, hold the rope tightly and pull it hard, and then the teacher pulls it from the middle of the rope with two fingers. As a result, both boys are pulled over.
The teacher continued to ignite the atmosphere: the teacher can not only easily pull two boys with two fingers, but also pull the bus with one hand. Unfortunately, this cannot be demonstrated live. Watch a video! (Playing video)
The teacher left a suspense: why can the teacher "dial a thousand pounds in four or two" Through today's study, students can explain this phenomenon well.
The teacher made clear the meaning of the content of the class: last class, students have learned that sometimes in order to facilitate the study of problems, several forces can be replaced by one force, which is the synthesis of forces. In fact, in many cases, a force can produce multiple effects. In order to study the practical needs of the problem, we must replace this force with several forces, which is the decomposition of forces. Just now, for example, two students were tug-of-war, and the teacher applied a horizontal pull in the middle of the rope, which produced the effect of pulling two students at the same time. To explain this phenomenon, we must learn the knowledge of force decomposition. Now we study the decomposition of force from a simple point of view.
[Probe into Teacher-student Interaction I]
(Photo display: Tractors pull rakes, while people pull boxes! )
Teacher's question conversion: students look at pictures on the screen, in which objects are pulled obliquely upwards. What effect does this pull have on objects?
Teacher: Next, we use experiments to explore.
Experimental exploration between teachers and students: We put a car on the scale of dynamometer and mark the position of the pointer. One end of the car is connected to the force sensor with a string, and students can read the tension value directly on the screen. The other end of the car passes through the pulley hook code with a thin rope, giving the car an oblique upward pulling force. Here we hang a hook code with a weight of 4.9N. Please write F=4.9N on your study plan.
The teacher asked the students 1: What phenomena did the students observe in the readings of the platform scale and sensors? Please describe it!
(The sensor didn't read before, but now it reads, and the reading of the platform scale is reduced. )
The teacher continued to ask: What effect did this show in the car?
(The effect of pulling the car vertically upward and the effect of pulling the car horizontally to the right) (The teacher praised and encouraged the students in time)
Essay 3 on decomposition of force model
Teaching objectives:
Knowledge and skills
1, understand the concepts of component and force decomposition.
2. The decomposition of knowledge and the synthesis of force are reciprocal operations, both of which obey the parallelogram law of force.
3, master the general steps of decomposition according to the effect of force, and learn to judge the actual effect of a force.
(2) Process and method
1, strengthen the idea of "equivalent replacement".
2. Cultivate the ability of observation and experiment.
3. Cultivate the ability to use mathematical tools to solve physical problems.
4. Cultivate the ability to analyze problems with body language.
(3) Emotion, attitude and values
1. Cultivate students' habit of exploring things around them by analyzing daily phenomena.
2. Cultivate students' awareness of expressing opinions and their desire to communicate with others.
Teaching focus
In practical problems, how to decompose forces according to their functions.
Teaching difficulties
How to determine the effect of a force?
teaching method
Analyze daily phenomena, ask questions, guide exploration, practice experience, discuss and communicate, and describe the decomposition method of output in physical language.
training/teaching aid
Building blocks, rubber bands, spring scales, pencils, thin threads, hook codes, multimedia courseware.
teaching process
Introduce a new course
Student activity: watch the video of the car automatically getting up and down.
Transition introduction: I believe that students will understand the truth after learning today's lesson.
Decomposition of blackboard writing force
New curriculum teaching:
Question: (Review, pave the way) What is resultant force? What is a component? What is the composition of force? What is the law of force composition?
The student replied: If the force has the same function as a force, this force is called the resultant force of the force, and the force is called the component of this force. The process of finding the resultant force of several forces is called force synthesis.
The combination of forces follows the parallelogram law.
We call it the decomposition of force, which guides students to understand the process of resultant force of objects.
Write on the blackboard 1. Finding the component of a known force is called force decomposition.
Guide students, then, what law should be followed in the decomposition of force?
Students think and answer: They should also follow the parallelogram rule.
Blackboard 2. The decomposition of force follows the parallelogram law.
Guiding students to reason that the decomposition of force and the synthesis of force are inverse operations.
There is no limit to the introduction of transition. A diagonal line can make countless groups of parallelograms, that is, a force can be decomposed into countless groups of different components, as shown in the right picture.
In practical problems, the role of force is often certain. How to decompose a known force?
Teacher's activity: demonstration experiment: hang a heavy object on the rubber band.
What phenomenon can be observed? What is the reason?
2. What effect does the weight have on the vertical downward pulling force F of the rubber band?
3. Can this effect be achieved with two forces F 1 and F2? What is the direction?
Teacher guides students]: Can you achieve the same effect by applying force along the elongation direction of two rubber bands? That is, F 1 and F2 are two forces instead of force F?
If F 1 and F2 have the same effect as F, then F 1 and F2 are two components of F (decomposition process of multimedia presentation).
In practical problems, the role of force is often certain. Through analysis, we can find out its function, thus determine the direction of the two-component force, and then decompose it to get a unique definite solution.
Blackboard 3, usually according to the role of force decomposition.
Transition introduction: The key to force decomposition is to determine the actual effect of a force.
Student activities: Discuss and communicate: What is the function of gravity G on the ball as shown in the picture? How does the function of gravity g decompose gravity?
Students think, discuss and answer the actual effect analysis: if there is no gravity,
Will there be extrusion between the object and the inclined plane and baffle? Don't! So two practical effects of gravity
The effect is that there is extrusion between the object and the inclined plane, and the object slides down to make the object.
There is extrusion between baffle and baffle.
Teacher guides students]: Can the same effect be achieved with the force perpendicular to the slope and baffle and the force passing through the ball and its contact point? That is, the two forces g' and g'' are equivalent to the replacement force g?
G' and G'' have the same effect as G, and G' and G'' are two components of G (decomposition process of multimedia presentation).
Let's explore two common examples:
Example 1 An object placed on the horizontal ground is subjected to an oblique upward pulling force F, and F forms an angle θ with the horizontal direction, as shown in the figure. How does force f decompose according to its function? What are the sizes and directions of its two components?
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