Centripetal force teaching plan Fan Wenyi
Knowledge and skills:
Know the concept, source, formula and physical meaning of centripetal force.
Understand the method and basis of circular motion analysis when learning general curve motion.
Process and method:
Through learning, Newton's second law consciously shifted from linear motion to circular motion.
Emotional attitudes and values:
Through discussion and communication, students' thinking ability and analytical ability are cultivated, and their enthusiasm for exploring problems is cultivated. Focus on the concept of centripetal force, the source of centripetal force, the relationship with centripetal acceleration, the difficulty of teaching AIDS, the key points of learning plan teaching: the concept, source, formula and physical significance of centripetal force.
Special attention: the source of centripetal force
Knowledge Link: centripetal acceleration and Newton's Second Law
Teaching process: link teaching, content learning, teacher-student interaction, pre-class design and design.
The representative of centripetal acceleration's physical meaning and formula report spoke. Listen carefully, evaluate and supplement, and lay a good foundation for the new course.
Guiding learning
go one's own way
study
cooperate
Explore that acceleration is produced by resultant force, so how is centripetal acceleration produced? We will study this problem in this class.
First, uniform circular motion and centripetal force
1. centripetal force: the resultant force on an object in uniform circular motion.
2. Formula: Fn= or Fn=.
3. Source: The centripetal force in uniform circular motion may be an external force on the object or a component of a force. Centripetal force is a named force, which can be provided by gravity, elasticity, friction and so on. , or determined by the resultant force of these forces or their components.
4. Function: Generate and change the direction of linear velocity.
1. device: hang a steel ball under the thin iron wire, and push the steel ball by hand to make it make a circular swing in a certain horizontal plane, as shown in the figure.
The teacher asked questions.
Students listen carefully, think carefully, and prepare to enter a new class.
Read the textbook and complete the study plan.
Through examples, the origin of the name of centripetal force is obtained
Combining Newton's second law and centripetal acceleration's formula, the centripetal force formula is derived.
Students explore in groups and teachers guide them. Explain the main research direction of this section and remind students to enter the state.
Read the textbook and extract the essence.
Let the students know the source and direction of centripetal force through the scene display.
Strengthen oral English
Gossip about sb.' s mistakes
effective
train
show
Communication 2. Seeking centripetal force and resultant force:
(1) Fn= can be used to calculate the centripetal force required by the steel ball.
(2) The resultant force f of the sum can be calculated.
3. Conclusion: By comparing the calculated centripetal force Fn with the resultant force F exerted on the steel ball after substituting the data, it can be concluded that what the steel ball needs is equal to the external force exerted on the steel ball.
Example: As shown in the above figure, a pendulum ball with a mass of m is hoisted by a long string L, and the upper end is fixed, so that the pendulum ball moves in a uniform circle in the horizontal plane, and the string will rotate along the conical surface, thus forming a conical pendulum. About the force of conical pendulum, the following statement is correct ().
A. The swing ball is influenced by gravity, tension and centripetal force.
Centripetal force teaching plan Fan Wener
design principle
Constructivism teaching theory inspires us to change our teaching concept, create a "student-centered, teacher-led" teaching environment, let students complete their tasks in real situations, change our long-term indoctrination teaching in which teachers speak on stage and students listen in the audience, give full play to students' autonomy in learning, guide students to actively discover, analyze and solve problems, actively construct a good cognitive structure and cultivate innovative spirit.
Textbook analysis
First, through examples, the textbook allows students to analyze the mechanical characteristics of objects from the perspective of motion and force, so as to get the concept of centripetal force, which is helpful for students to experience and understand. According to Newton's second law, the mathematical expression of centripetal force is deduced from the theoretical point of view. After that, in order to make students have a certain knowledge and understanding of the centripetal force formula, a verification experiment is designed in the textbook: the expression of centripetal force is roughly verified with a conical pendulum. Through the conical pendulum experiment, the distance between science and life is narrowed, and students feel that science is around and have a sense of intimacy with science.
This section is also different from the past, that is, after discussing uniform circular motion, we discuss variable-speed circular motion and general curvilinear motion. The supplement of this content not only provides a theoretical basis for analyzing the force analysis and motion of objects at the highest and lowest points of the curve, but also provides students with a way of dealing with problems: from special to general.
The study of this part of knowledge can make necessary preparations for the motion of gravity and charged particles in a uniform magnetic field. Of course, after learning this section, all the forms of sports in middle schools have been learned, so that students can understand the relationship between sports and strength from a broader perspective.
Analysis of learning situation
Through the study of the previous sections, the students learned the conditions of curve motion, the important method of dealing with curve motion-the synthesis and decomposition of motion, and also learned the flat throwing motion by using the knowledge of synthesis and decomposition of motion. Then physical quantities such as angular velocity, linear velocity, period and rotational speed are introduced to describe the law of uniform circular motion. The study of this knowledge prepares students for learning centripetal force.
Because centripetal force is a force that students are unfamiliar with, and the abstract thinking ability and logical reasoning ability of senior one students are not very strong, it is necessary to sublimate students' understanding of centripetal force from perceptual knowledge to rational knowledge through examples and experiments in teaching.
Teaching objectives
1. Knowledge and skills
(1) Know what centripetal force is and understand it as an effective force.
(2) Understand the exact meaning of centripetal force formula and use it for simple calculation.
(3) Know that the centripetal force is a component of the resultant force in the circular motion with variable speed, and know the function of the resultant force.
2. Process and method
(1) Let students understand the concept of centripetal force by exploring it. And master the general methods of dealing with problems: asking questions, analyzing problems and solving problems.
(2) In the process of verifying the expression of centripetal force, I realized the role of the control variable method in solving problems.
(3) Through the research process from uniform circular motion to variable circular motion and then to general curvilinear motion, let students understand the thinking method of solving problems from special to general. And learn to analyze and solve problems from the perspective of movement and force.
3. Emotional attitudes and values
(1) Experience the research process from special to general, and cultivate students' ability to analyze and solve problems.
(2) Examples, experiments and life are closely linked, which narrows the distance between science and students, makes students feel that science is around, mobilizes students' enthusiasm for learning and cultivates students' interest in learning.
Important and difficult
1. Teaching focus
(1) Understand the concept of centripetal force and establish the formula.
(2) Understand the formula of centripetal force and use it for calculation.
(3) Understand that centripetal force only changes the direction of speed, but does not change the size of speed.
2. Teaching difficulties
(1) Understand the concept of centripetal force and establish the formula.
(2) Understand that centripetal force only changes the direction of speed, but does not change the size of speed.
Teaching strategies and means
Centripetal force is an important and difficult content in senior high school physics. When analyzing the force of an object, it is often unclear what force provides centripetal force during the movement, which shows that students' understanding and understanding of centripetal force is not deep and comprehensive enough. In order to break through the difficulties, teachers stimulate students' desire for knowledge through concrete examples and experiments in teaching, so that students can actively participate in the process of inquiry, become the main body of learning, and actively acquire knowledge and ability.
The teaching process of this course is designed as follows: creating situations → finding problems → guessing → theoretical derivation → experimental verification → drawing conclusions → guiding practice.
In teaching methods, PPT, video, demonstration experiment and story telling are fully used to enhance the vividness and vividness of teaching and enliven the classroom atmosphere, so as to fully mobilize students' learning enthusiasm and implement teaching objectives.
Preparation before class
1. Experimental instruments: steel ball with rope (one for two people), iron frame, one steel ball, one rope, scale, round bottle cap, stopwatch, stopper and round bottle cap.
2. Video: Bicycle turning, swivel chair in the park.
3. make PPT.
teaching process
First, the introduction of new courses.
Demonstration experiment: let the object do circular motion as uniformly as possible on the rotating platform.
Teacher: Why can a building block do uniform circular motion? We will study this problem in this class.
(Design intention: Introduce from experiments to stimulate students' curiosity and enliven the classroom atmosphere. )
Second, the new curriculum teaching
centripetal force
1. The concept of centripetal force
Student: Under the guidance of the teacher, analyze the force of the wood block: the wood block is subjected to gravity, friction and support.
Teacher: What is the resultant force on the block?
Student: Gravity and supporting force cancel each other out, and the resultant force is friction.
Teacher: What are the characteristics of this resultant force?
Student: Think and answer: The direction points to the center of circular motion.
Teacher: Get the definition of centripetal force: the resultant force pointing to the center of the circle when an object moves in a uniform circle.
Do a good job of connecting the old knowledge with the new knowledge, so that the concept can be drawn naturally and smoothly. )
Feel centripetal force
Student: Students hold one end of the rope with their hands, so that the steel ball with the rope moves in a circle as uniformly as possible in the horizontal plane.
Teacher: The steel ball moves in a circle as uniformly as possible in the horizontal plane. What force makes the steel ball move in a circle?
Student: The stress analysis of the steel ball shows that the tension makes the steel ball move in a circle.
(Design intention: Let students experience it with common small experiments, and enhance the perceptual knowledge of centripetal force. )
Teacher: That is to say, the tension of the steel ball plays the role of centripetal force of circular motion. Let's do experiments and guess: which factors are related to the tension?
Student: Hands-on experience and conjecture: the magnitude of the pulling force may be related to the mass m, linear velocity v, angular velocity, period t and radius r of the steel ball.
Teacher: So how do we study the relationship between centripetal force and M, V, T and R?
Student: Think, discuss and answer: Keep the four quantities of M, V, T and R unchanged by the method of control variables, and study the relationship with the remaining quantity.
Teacher: If the mass m, linear velocity v, angular velocity and period t of the steel ball remain the same, can the radius r be changed?
Student: Under the guidance of the teacher, think and answer according to the relationship between various physical quantities: the radius r cannot be changed.
Teacher: So how do we study the relationship between these physical quantities?
Student: Think, discuss and answer: An object moves in a uniform circle. As long as two of the four physical quantities V, T and R are determined, the other two quantities are determined. So we only need to study the relationship between centripetal force and two of the four physical quantities m, v, t and R.
Teacher: Guide students to do experiments by controlling variables and experience the magnitude of centripetal force.
Student: Do experiments by controlling variables and experience the magnitude of centripetal force.
Teacher: What is the relationship between centripetal force and the physical quantity after each person's experience?
Student: According to your own experience and answer:
The mass m and radius r are fixed, and the greater the linear velocity v, the greater the centripetal force;
The mass m and linear velocity v are constant, and the greater the radius r, the greater the centripetal force;
The mass m and radius r are constant, and the greater the period t, the smaller the centripetal force. ...
(Design intention: actively guide students to guess and infiltrate the experimental method: the teaching of control variable method. )
3. Derive the expression of centripetal force
Teacher: This is a possible qualitative relationship between centripetal force and various physical quantities. Then can you theoretically derive the expression of centripetal force from what you have learned?
Teacher: Under the guidance of the teacher, according to centripetal acceleration's expression and Newton's second law;
Because, so =
Centripetal force teaching plan Fan Wensan
I. teaching material analysis
Analysis of curriculum standard: Newton's second law can be used to analyze the centripetal force of uniform circular motion.
Teaching Material Status: The centripetal force part is the key and difficult point of the curve movement in Chapter 6 of the compulsory course 2 of the experimental teaching material of the curriculum standard in ordinary senior high schools, which has the function of connecting the past with the future. It is not only an inflection point of this chapter's knowledge, but also an important basis for the expansion of this chapter's content; Through learning, students can not only improve their superficial understanding of circular motion to theoretical analysis, but also improve their analysis of circular motion in life to the analysis and deduction of celestial motion and charged particle motion in electromagnetic field. At the same time, centripetal force can fully reflect the importance of force and movement in physics, and it is a good material to learn the relationship between movement and force.
Second, the analysis of learning situation
Through the previous study, students can understand the relationship between mass, force and acceleration, understand the physical quantities describing circular motion and their relationship, and know that uniform circular motion points to the centripetal acceleration of the center of the circle. Moreover, students have experienced the learning process of mutual cooperation, mutual discussion, mutual exchange and finally showing their achievements, and have a general way of thinking to deal with problems: asking questions-analyzing problems-solving problems.
Third, the teaching objectives
Knowledge and skills
1. Understand the concept of centripetal force, and know that centripetal force is a force named according to the function of force.
2. Knowing which factors are related to centripetal force, we can make simple scenario calculation.
3. It is known that in the circular motion with variable speed, the normal component of the resultant force provides centripetal force and the tangential component is used for acceleration.
4. Know the processing method of general curve motion.
(2) Process and method
1. Through the exploration and experience of the concept of centripetal force, let students understand the connotation of its concept. And familiar with the general methods of dealing with problems: asking questions, analyzing problems and solving problems.
2. In the process of verifying the expression of centripetal force, realize the role of physical experiment in solving problems.
3. Through the research process from uniform circular motion to variable circular motion and then to general curvilinear motion, let students understand the thinking method of solving problems from special to general. And learn to analyze and solve problems from the perspective of force and movement.
Emotions, attitudes and values
1. Cultivate students' problem awareness and thinking ability through the process from asking questions to solving problems by themselves.
2. Experience the research process from special to general, and cultivate students' ability to analyze and solve problems.
3. Examples, experiments and life are closely linked, which narrows the distance between science and students, makes students feel that science is around, mobilizes students' enthusiasm for learning and cultivates students' interest in learning.
Four, the focus and difficulty of teaching
1. Teaching focus
Understand the concept and formula of centripetal force and the relationship between supply and demand in uniform circular motion, and can make simple judgments and calculations. Will analyze the source of centripetal force
2. Teaching difficulties
Understand that centripetal force is an effective force, analyze the source of centripetal force, and understand the relationship between supply and demand in uniform circular motion
Teaching process of verbs (abbreviation of verb)
Teaching plan Teaching content Students' active thinking dialogue students' pre-class experiments;
Take the electric toy racing car as the research object, as shown in the figure, draw a circle on the ground as the trajectory of the racing car. Pass the rope through a hollow fence. One end of the rope is tied with a toy racing car and the other end is tied with a spring dynamometer. Pay attention to the reading of the spring dynamometer.
Mutual cooperation
Observe the phenomenon
Phenomenon:
When the car is moving in a uniform circular motion, the spring dynamometer has a number and its size remains unchanged.
The problem of knowledge review 1: Review: the essence of uniform circular motion.
Question 2: Review: The physical meaning, definition, direction and size of centripetal acceleration.
Question 3: Review: The content and expression of Newton's second law.
Look at the previous notes and review what you have learned 1. The linear velocity and angular velocity of an object moving in a uniform circular motion are constant (the period is constant).
2. Physical meaning: a physical quantity describing the changing speed of linear velocity of an object moving in a uniform circle.
Definition: the acceleration pointing to the center of the circle when an object moves in a uniform circular motion.
Direction: always point to the center of the circle.
Size:
3. Content: The acceleration of an object is directly proportional to the acting force and inversely proportional to the mass of the object, and the direction of acceleration is the same as that of the acting force.
Expression: F=ma
Situation introduction
1. Perceived centripetal force
Question 1: What did you observe in the experimental activities before class?
Question 2: Now, please pick up the prepared rope with a small rubber at one end and let it make a uniform circular motion on the smooth desktop (pay attention to safety). Tell me how you feel.
Transition: It can be seen that an object in uniform circular motion has a force pointing in the direction of the center of the circle. Let's explore this power together in this class.
Students' own activity experience
1. When the car moves in a uniform circular motion, the number and size displayed by the spring dynamometer remain unchanged.
2. Feel the powerful effect of the rope on the opponent
Looking for centripetal force
Question 1: Please watch the video and answer: (1), what does the earth do around the sun? (2) Why does the earth do this movement around the sun?
Question 2: Did you analyze the force of the object in uniform circular motion in the above question 2 and find out the resultant force?
Question 3: Let the students think about how to make a small rubber with a rope do a uniform circular motion different from Question 2. Establish a physical model and analyze its force to find out the resultant force?
Question 4: Through the above example, the stress characteristics of uniform circular motion are summarized.
Transition: In front of us, we studied the acceleration that always points to the center of the circle in uniform circular motion-centripetal acceleration. According to Newton's second law, the cause of centripetal acceleration must be that the object is subjected to the resultant force pointing to the center of the circle. This resultant force is called centripetal force.
Think independently and complete the stress analysis diagram.
group discussion
Get 1. (1). The earth moves approximately in a circle around the sun, and also in a uniform circle.
(2) The sun has a gravitational effect on the earth.
2.=F
3.( 1)=T
(2)=
Mechanical characteristics of uniform circular motion;
1. can bear one force or multiple forces.
2. The resultant force points to the center of the circle
3. The resultant force can be elastic force, gravity, friction force or the resultant force or component of these forces. 3. Do you know the centripetal force
Question 1: On the basis of summarizing the above questions, please give the definition, direction, size, characteristics and function of centripetal force.
Question 2: Some students think that the expression of centripetal force is: =; Some students think that this is based on Newton's second law:
Which of these two formulas do you think is correct? If they are all correct, please tell me from what angle.
Interlanguage: Can these two expressions be equal? Is the resultant force provided equal to the required centripetal force? Experiments are needed to verify it.
Summarize, exchange views and take notes.
Discuss, think and answer.
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