“质点”这个概念是高中物理提出的第一个理想化模型,其基础性显而易见,它也是人教社新版高中物理必修一中第一节的核心,在教学中流行着一些似是而非的说法,在几乎所有的高中教辅资料、甚至期中期末考试卷中差不多都有这样的观点:例如,一列火车从北京开到广州,①在研究火车的整体运动时毫无疑问可以把火车看做质点,理由是火车的长度可 The concept of “mass point” is the first idealized model put forward by high school physics. Its basic nature is obvious. It is also the core of the first section of the new edition of the senior high school physics required by the People’s Education Agency. There are some plausible arguments in teaching. In nearly all high school teaching materials and even mid-term exam papers, there is almost such a point: for example, a train travels from Beijing to Guangzhou, and there is no doubt that the train can be regarded as a mass when studying the overall movement of trains. The reason is that the length of the train can be