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机械效率问题是初中物理教学中的难点之一,也是考试中的热点内容.此类问题涉及有用功、额外功、总功、功率等诸多概念,许多学生由于对这些概念理解不深,不能正确领会这些概念间的区别与联系,往往在解题时感到困惑.下面结合自己多年的教学体会,就以下几个问题谈一些看法.问题一如何正确区分有用功和额外功?
The problem of mechanical efficiency is one of the difficulties in junior middle school physics teaching, and it is also a hot topic in the exam. Such problems involve many concepts such as useful work, extra work, total work, power, etc. Many students cannot understand the concepts because they do not understand these concepts deeply. Understanding the differences and connections between these concepts is often puzzling when solving problems. The following combination of years of teaching experience, on the following questions to talk about some of the views. Question 1 how to correctly distinguish between useful work and extra work?