An "unexpected" problems inquiry activityIn the new curriculum reform of basic education, scientific inquiry, not only as science subject curriculum, and as the content was incorporated into the _ content standards, this is essentially to strengthen inquiry teaching goals into reality requires. Science teachers, enhance the ability to carry out exploring teaching became a natural request.
First, the problem of simple mechanical design and attractive leverage is a commonly used. Usually only talk about a fixed axis of rotation, as shown in the case with fixed hinges, the equilibrium conditions: =. In some cases, the axis of rotation of the object there are two or more, the studies tend to choose one of them to fix the hinge, the problem can be solved. As shown in the example problems, can be analyzed as a fixed axis of rotation, then in another stretch on the hinge is fixed axis of a rotating the lever counterclockwise. According to the survey, many students have rotating axis problem, often blindly without in-depth analysis formula. In teaching activities in the, teachers can created loose of environment, through some conducive to inspired students in-depth inquiry of problem, let students for independent of inquiry, makes students not only get knowledge Shang of consolidation and upgrade, and change "assumed" of thinking set, widened thought, training dared to questioned of attitude and innovation of consciousness? based on such of idea, we using homemade of experiment device, for has once inquiry sex learning activities of attempts to. , Rectangular beam rotating boxes are light weight, high strength materials together. For simple considerations, a shaft are ball point pen refill sleeves, copper rod and shaft combinations of "easy bearing", and hinge-centric, dimensions, quality of both sides of its strict symmetry. Using a thin wire as shown in the linked code. We form a picture of the device in front of students, and ask questions: "which 1 ≠ 2, loaded spring balance status?, please state the reasons, verified and specific experiments."
Second, students explore the answer to the question is not "visible" in the face of this problem, but most of them quickly to make sure thinks the correct answer: couldn't keep his balance. Because the whole device as leverage. , On a straight and perpendicular to the beam, can be handled as a hinge, so the "leverage" couldn't keep his balance. Can be seen from their facial expressions and tone, he, such a "simple" problems are clearly dismissive. Although some students think that the matter is not so simple, but after thinking it over for a while after, also made similar conclusions. ' After the student judge, on their view, teachers did not give either positive or negative, but to provide them with physical, let them experiment on their own judgments for validation. After the experiment, the phenomenon, they were surprised and confused. Many people experiment over and over again, always wanted to see my expectations on the same phenomenon, but let them down – "leveraged" remains balanced! to this, students were bewildered, lost in thought, there's constantly saying "it is impossible, impossible!". But * all * real, they realized that the answer to the question is not "obvious" to trying to understand why, for further inquiry.
2. Maintain for a longer period of time has passed, after their respective thinking, students formed two opinions: one is the "friction" point of view, and the other is "elastic" view. In order to prove it, they discussed the analysis, teachers ' organizations. Some students think that: as the shaft friction existed, leading to a "device to maintain balance." They rotates the friction force size, orientation, and its impact on device balanced analyses, and the method to reduce friction. But after they used lubricants reduce friction, there is no change. Teachers and for they provides has they himself are think friction enough small of, with micro precision bearing alternative above simple "combination bearing" of new device, repeatedly for experiment, but phenomenon still old! another some students is proposed: with as Figure 2 by shows of situation on device of balance problem for explained, that put device in the of () 1 as fixed turned axis, because 11≪22, "lever" has counterclockwise turned of trend, 2 Shang is can provides makes lever clockwise turned of stretch, makes "lever" balance.