“讲授物理定律,要讲清它的内容和条件”。这是常听到的经验之谈,但对其中的“条件”一词,却似乎没有统一的理解。譬如我们可以说,“根据牛顿第二定律,受力是使物体产生加速度的条件”,同时也可以说:“牛顿第二定律的成立,是以宏观、低速、惯性系为条件的。”这两句话里都提到“条件”,但含义显然不同。 “Teach the laws of physics and explain its contents and conditions.” This is an often-talked experience, but there seems to be no uniform understanding of the term “conditions.” For example, we can say, “According to Newton’s second law, stress is the condition that causes an object to produce acceleration.” At the same time, it can also be said: “The establishment of Newton’s second law is based on macroscopic, low-speed, and inertial systems.” In both sentences, “conditions” are mentioned, but the meaning is obviously different.