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在进行高中物理总复习时,我选择了下述例题: 题1.把一个摆长为0.54米的单摆拉至跟悬点N在同一水平面上,并在悬点正下方且距悬点0.27米处垂直于摆线平面钉一钉子P(图1),然后自由释放摆球,则摆球最高能上升到何处? 问题提出后,许多同学脱口而出:“仍会上升到原来高度!”“为什么?”“因为机械能守恒。”甚至有的同学举出《物理》(甲种本)第一册,第241～242页练习六的第(2)题(见题2)为例,指出“不管钉子钉在何处,摆球都能升到原来的高度”。这个题目如题2: 题2.做下面的实验。把物体拴在细线上悬挂起来,做成一个单摆(图2)。把物体从平衡位置O拉到B,放手后观察物体来回摆动。把铅笔放在1和2,可以看到物体仍然要升到跟B同样高的C_1和C_2,解释这个现象。
In the review of high school physics, I chose the following example: Question 1. Pull a pendulum with a pendulum length of 0.54 meters to the same level as the hanging point N, and just below the hanging point and 0.27 from the hanging point. At a meter perpendicular to the cycloid plane, a nail P (Figure 1) is nailed, and then the pendulum ball is free to release, then the pendulum ball can rise up to where? After the question is raised, many students blurted out: “The height will still rise to the original height!” Why does “” mean?“” Because mechanical energy is conserved.“ Some students even cited the first volume of Physics (A type of book), and the second (2) of Exercises 241 to 242 (see question 2) As an example, it is pointed out that ”The pendulum ball can rise to its original height no matter where the nail is nailed." This topic is covered in Question 2: Question 2. Do the following experiment. Hang the object on a thin line and make it a single pendulum (Figure 2). Pull the object from equilibrium position O to B and let go and watch the object oscillate back and forth. Put the pencil on 1 and 2 and you can see that the object still rises to the same high C_1 and C_2 as B, explaining this phenomenon.