First, the reverse thinking method
Reverse thinking is a scientific thinking method to solve physical problems. For some questions, using conventional thinking methods will be very complicated and even impossible to answer. Using reverse thinking, that is, taking the "final state" of the movement process as the "initial state", to study the problem reversely can make the physical scene simpler and the physical formula simplified, thus making the problem easy to solve and get twice the result with half the effort.
Second, the symmetry method
Symmetry is a kind of invariance when things change. There is a beautiful and harmonious symmetry phenomenon in nature and natural science. When using symmetry to solve a problem, the answer may be clear at a glance, which greatly simplifies the steps of solving the problem. From the perspective of scientific thinking methods, the most prominent role of symmetry is to inspire and cultivate students' intuitive thinking ability. The key to solving problems with symmetry method is to keenly see and grasp the symmetry of things in a certain aspect, and these symmetries are often the shortcut to the answer.
Third, the image method
Images can intuitively describe the physical process, vividly express the physical laws, and vividly express the relationship between physical quantities, which has always been a common tool in physics, and the image problem is also a knowledge point that must be tested in the college entrance examination every year. Using physical images to deal with physical problems is a comprehensive embodiment of the ability to read and draw pictures. Usually qualitative drawing is the main method (sometimes quantitative drawing is needed). When it is too difficult to analyze some physical problems, it is often difficult to simplify the complex and turn the difficult into the easy.
Assumption is to assume certain conditions before reasoning. If the result is consistent with the phenomenon of topic setting, the hypothesis is established, otherwise the hypothesis is not established. Assumptions commonly used to solve physical problems include hypothetical physical scenarios, hypothetical physical processes, hypothetical physical quantities, etc. Using assumptions to deal with some physical problems can often break through thinking obstacles and find new ways to solve problems. This method is often used to analyze the common direction of elasticity or friction.
Five, the whole, isolation method
Physics exercises often involve more than one single object, an isolated process or a single condition. At this time, many objects, processes and unknowns involved can be considered as a whole, and this method of solving problems with the whole as the research object is called the whole method. The method of extracting a part (such as an object or a process) from the whole for analysis and research is called isolation method.
Six, graphic method
Graphic method is a method to make a graph according to the meaning of the question to determine the correct answer. It is simple, clear and intuitive. Using it to qualitatively analyze some physical problems can get twice the result with half the effort. In particular, it is often used to solve the balance problem of an object subjected to three forces (the magnitude and direction of one force remain unchanged, and the direction of the other force remains unchanged).
Seven, conversion method
Some physical problems are difficult to solve because of the complexity of the movement process or the difficulty of force analysis. In this case, the reference system or the research object should be transformed according to the relativity of motion or Newton's third law, which is called transformation method. The application of this method can make the problem from difficult to easy, and the process of solving the problem is clear at a glance. Eight. procedural law
The so-called programmed method is to analyze the physical processes given by the topic in chronological order, correctly divide different processes, specifically analyze the relationship between speed, displacement and time for each process, and then use the specific characteristics of each process to solve the problem. The key to solving problems by programming method is to correctly select the research object and physical process, and pay attention to two points: First, pay attention to the speed relationship, that is, the final speed of 1 process is the initial speed of the second process. The second is the displacement relationship, that is, the sum of the displacements of each segment is equal to the total displacement.
Nine, extreme law
Some physical problems, because physical phenomena involve many factors and the process changes are complex, it is often difficult for students to gain insight into their changing laws and make judgments quickly. However, if the problem is pushed to an extreme state or a special state for analysis, the problem will immediately become clear and intuitive. This method of solving problems is called extreme thinking method, also called extreme method.
The key to solving physical problems with extreme thinking is to consider what extreme the problem should be pushed to, that is, to choose a good variable, and the selected variable should have an extreme value or critical value in the process of change, and then analyze the changing law of the problem from the extreme state, so as to solve the problem.
Some problems may be complicated if they are calculated directly. If you substitute a special value that conforms to the laws of physics, you will make a quick, accurate and flexible judgment. This method is especially suitable for multiple-choice questions. If the options in multiple-choice questions are referential or mutually exclusive, it is easier to choose the correct answer by extreme value method, which highlights the advantages of extreme value method. Strengthening this kind of training is conducive to cultivating students' divergent thinking and creative thinking.
Extreme value method
There are two common extreme value problems: one is to directly point out that a physical quantity has an extreme value and find its extreme value; The other is to solve related problems by finding the extreme value of a physical quantity. Two typical solutions to physical extremum problems.
(1) The first solution is to analyze the physical concepts and laws involved in the physical phenomena given in the problem, make clear the conditions under which the physical quantities in the problem take the extreme value, or what physical characteristics exist when the extreme value appears, and then look for the extreme value according to these conditions or characteristics. This method highlights the physical essence of the problem. This solution is called the physical method to solve the extreme value problem. (2) The second solution is to establish equations according to the physical laws followed by physical problems, and then carry out mathematical derivation according to these equations. In the derivation, the extreme value is obtained by using the existing conclusions in mathematics. This method focuses on mathematical derivation, which is called physical-mathematical method to solve extreme value problems.
This extreme problem can be solved in many ways:
(1) arithmetic-geometric average method, i.e.
A. If the sum of two variables is a certain value, when the two numbers are equal, their product is the largest. B. If the product of two variables is a certain value, when the two numbers are equal, their sum will be minimized.
(2) Using the discriminant of quadratic function to find the discriminant of the root of extreme quadratic equation AX2+BX+C = 0 (a ≠ 0), which has the following properties:
δ= B2-4ac & gt； 0—— The equation has two real number solutions; δ= B2-4ac = 0- The equation has a real number solution; δ= B2-4ac & lt； The 0- equation has no real number solution.
Using the above properties, we can find the extreme value of a function, which can be transformed into the form of AX2+BX+C = 0. XI。 Estimation method
Physical estimation generally refers to roughly calculating the size or range of physical quantities by using physical methods and approximate calculation methods according to certain physical concepts and laws. Physical estimation is an important method. Some physical problems can be simply dealt with by approximate methods on the premise of accuracy. Some physical problems, due to the particularity of their own conditions, do not need and cannot be accurately calculated. In this case, estimation becomes a special method with scientific and practical value.
Twelve. Conservation thought
Conservation laws such as energy conservation, mechanical energy conservation, mass conservation and charge conservation all embody an essential law of nature-"constancy". Learning physics knowledge is to explore the physical laws of nature, so what are the physical laws of nature? In the ever-changing physical phenomena, the constant "thing" is the essential factor that determines the change and development of things.
From another point of view, it is precisely because there are a lot of conservation phenomena and laws in the material world that conservation ideas and methods are provided for us to deal with physical problems. Conservation laws such as energy conservation and mechanical energy conservation are the main tools for us to deal with physics problems in senior high school. Analyzing the transfer and transformation of energy and mechanical energy in physical phenomena is the main idea to solve physical problems. In the complex physical process, grasping the constant factor is the key to solve the problem.