比值定义法（Ratio definition method）
Discussion on ratio definition method
Zhang Jian1
百合粥的做法
The ratio definition is defined as the ratio when defining a physical quantity. The physical concepts defined by the ratio method occupy a large proportion in physics, such as speed, acceleration, power, electric field intensity and magnetic induction intensity, etc..
First, the definition of ratio
The ratio definition method is suitable for the definition of material properties and object movement characteristics. Becau they will show some properties in and outside action, this will provide us with the u of external factors to reprent the characteristics of indirect way, often with a certain ratio of experiment for attributes and substances or objects on the two or more physical quantity which can be measured, can determine the new physics a characterization of this attribute. Using ratio method to define physical quantities often requires certain conditions: first, it is objectively needed; two is a physical quantity that can indirectly reflect characteristic attributes; three, the ratio of multiple physical quantities must be a fixed value.帆船逆风行驶原理
Two. Understanding of the ratio definition method
The formula of the ratio definition method can not be mathematically pure. In the establishment of physical
quantities, we should understand the physical ideas and methods, make clear the nature of the concept of expression, should not be formalized by mathematical symbols, ignoring the rich content of physical content. It is necessary to reveal the true dependency relationship between the concepts and the concepts concerned from the formula, and avoid rote memorization and misu. For example, the definition of speed is ud here is the ratio of motion speed, but the speed of motion object is not decided by this ratio; the speed of movement is also characterized as a whole, the exact meaning of displacement is the time rate of change, and not as simple combination, so there is no V and is proportional to the speed T, and inverly proportional to the. On the other hand, reprented by the proportion of the mathematics form of expression, not necessarily is the application of the ratio method of definition. For example, the acceleration formula, which is to be learned in the future, is only the mathematical definition of the ratio, but does not have the other characteristics of the ratio definition method. So we can't simply combine the ratio definition method with the mathematical formula.
澳大利亚国立大学
The ratio definition method is a commonly ud physics scientific method in junior high school physics teaching, and should be paid enough attention to.
桂林有什么好吃的The ratio of definition method is to u a ratio of two or more than two physical quantity method to define the addition of a new physical quantity, the esnce of this method is compared with the thought, its esnce is bad on the idea of control variables. The key to the comparison is to lect the same criteria (becau only the same criteria are chon, so that
the results of the comparison are meaningful). The ratio definition method, which us two or more than two physical quantities, is a basic means of lecting the same standard in comparison.
The physical quantities defined by the ratio definition method can be divided into two types according to their different meanings:
One is that the ratio of two or more physical quantities is a constant or a definite value, which belongs to the quality of x. Such as density, resistance, etc., the ratio reflects the nature of the material itlf, its size is only determined by the material itlf, and the definition of the other physical quantities in the form does not matter;
男生的帅气头像
The other is the description of the external state of the object or substance, the strength of the external function, and does not reflect its inherent nature, belonging to the state. Such as velocity, pressure, power and so on, its size is influenced by other physical quantities in the definition.
The two kinds of physical quantities defined by ratio are different in teaching.工作自荐信
(1) when the physical quantity defined by the ratio belongs to the x quality
Physical quantity ratio method to define the quality, often require certain conditions: one is the objective need of two is to indirectly reflect the two physical attributes can be
measured, three is the ratio of the two physical quantities must be a fixed value.
It is worth noting that in teaching, the corresponding ratio is defined only if the individual (or the same) ratio is obtained by analyzing one phenomenon or some property of a thing,
Instead of the same nature of things, or to compare the different phenomena of the same thing, it will cau the ratio of amount of lack of sufficient basis, the connotation of students is not easy to understand the concept.梦见死人周公解梦
Only when the students have a clear understanding of the qualitative and quantitative comparisons of the attributes of some different rearch objects, will the introduction of xual quality reflect the nature of the attribute (nature).
For example, the same volume density, different material quality, they are not equal, which indicates that the material in the nature is different, with a physical quantity to reflect the objective reality, it is necessary to define the conditional density; becau if different material quality of the same size are the same, there would not be need to establish the concept of the density.
Through repeated experiments, found that in the same matter quality, although the size is not the same, but the ratio is their quality with a constant volume; each kind of material are given a relatively constant and determined, and different kinds of material constants of the same volume of high quality, small
mass constant small. Thus, this constant can fully reprent the properties of matter. The physical quantity of density is introduced.
In the physics of middle school, the important concepts similar to the introduction of density are resistance, electric field intensity, magnetic induction intensity, etc..
(2) the physical quantities defined by the ratio are state quantities
For the definition of the ratio of objects or substances, the external state, the external effect of the strength of the amount of state, and other related factors may not be proportional.
The ratio method is ud to define the physical quantity which belongs to the state quantity, and usually only needs two conditions: one is the objective need, and the two is the two physical quantity which indirectly reflects the characteristic attribute. But in the teaching, we should pay attention to fully restore and show the ratio method to introduce physical quantity process, otherwi students feel difficult to understand.
For example, the introduction of the concept of speed: life experience tells us, to compare the speed of object movement, you can compare the distance at the same time of movement, or can compare the time in the same movement distance. If two objects move in different time and distance, how do they compare their speed? At this time, if the teacher told the students that
>isna函数
