The point total force equilibrium conditions Student design

New curriculum, high school physics curriculum standards: "high school physics course will help students continue to learn basic physics knowledge and skills, and to experience the process of scientific inquiry, understanding of scientific research methods, enhance creativity and practical ability ......" the target depends The traditional teaching methods can not be achieved. times call for new teaching mode, the modeling teaching has gradually widely adopted by many teachers, and demonstrated strong vitality.

Scientific abstract physical model of the actual problem, with one to reflect the characteristics of the original essence of the ideal substance or process or imaginary structure, to describe the actual thing or process modeling both a thought process, and a way of thinking study method, and its essence is hidden in the complex physical scenarios or physical process can be simplified, abstract, analog, refining the prototype physical model even idealized form of this model is the characterization of the physical system or the physical process of conceptualization, physical modeling aimed correctly characterize the physical scene modeling process should be rooted in the specific physical situations, through a variety of phenomena in the physical scene, the descriptive construct physical models between process variables and model analysis, discussion and inspection to form a model of a real physical sense, then the model analysis, processing and solving physical problems.

Integrated into the physical concept of the formation of the laws of physics to grasp and physical problems solve physical modeling and model applications, which is conducive to encourage students of physics consistency, flexibility and systematic understanding, help students experience science physical law is the result of the physical modeling activities, physical problems is a physical model of the application, will help students understand and master the general methods of physics research to explore the process, the need to experience the physical concepts introduced in the physical modeling process. conducive to the diligent Shansi students apply their knowledge and interest in physics lasting.

Modeling teaching, teachers should allow students in the actual scenario or the creation of the physical scene, experienced model and perfect model, the evaluation model, the application model several processes, prompting the students' understanding of the integrity of the modeling process, reached independently Modeling and answers to issues related to the use of a physical model.

Expected to preview]

(1 reviews common point force balance the role of features and follow the rules.
(2 read through the textbook, write out their own questions, to enter the classroom with a problem.

Learning objectives

(1 characteristics and follow the law to understand the role of the force balance of the total points.
(2 be able to use a total point force equilibrium conditions to solve common production and life Sanli (Sanli balance problems.
(3 witnessed problems explore the whole process, appreciate the triangle method, orthogonal decomposition proper application of the method.
(4 preliminary summarizes the formation of the basic ideas and methods to solve the balance problem.

Instruction for Learning]

Common point force balance of the object is the application of a special case of Newton's second law, namely, F = ma, where a = 0 Therefore, the analysis of the same ideas and methods and the application of Newton's laws of motion.

Students, let us work together to apply the equilibrium conditions to solve two practical problems!

(1 activity with a rope to the birdcage hanging on a beam, as shown in the following figure, if the the birdcage heavy 20 N demand pull rope OA and OB each is how much?
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guide issues: Available in several different ways to solve?

Guide issues: the size of the rope pull rope length about the relationship? Decide which physical quantity?

Guidance: the maximum pull on the same assumption that each rope, gradually increasing the mass of the object, which first off the rope?

Guiding Question 4: Suppose B O points do not move point A slow-moving to the left, the rope pull how changes?

Guidance: How to choose the thickness of the rope?

Guidance: solve the force balance problems commonly used method?

(2 activities of two workers in cartons moving on level ground, usually using both "pull" and "push" method, as shown in the following figure, the direction of the force of these two methods: Rally oblique and thrust under oblique.


Guiding Question 1: How to move the box more effort?

Guiding Question 2: When the angle θ is equal to the number, the minimum force F?

Guidance: the basic idea of ​​solving the balance problem is it?

Guiding Question 4: In the loading of the goods, the workers often by means of a ramp onto the cargo car, the model shown in the following figure, this slant can save much force?

Workers put weight 1000 N goods along the ramp onto the top the slant length 5 m, a height of 3 m. Kinetic friction between the goods and slope factor is 0.3. Assumed that the thrust direction is always parallel to the board, seeking workers handling thrust at least?
In summary, the advocate of independent learning, cooperative learning, inquiry learning today, in the classroom teaching learning plan designed many schools, I believe that learning plan must be designed to reflect the subject characteristics, school case design is different from the lesson plans and exercises, learning The case design is sure to highlight the Guidance guide thinking, guide function, learning plan designed to meet the cognitive ability of students. posted in the free papers Download Center http://eng.hi138.com

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