《机械效率》这节课主要包括建立有用功、额外功和总功的概念及理解机械效率两大方面的内容。它既是前面功及功的原理知识的延伸,又是探究斜面机械效率的基础。因此,它的地位就显得较为重要。一、对三种功概念理解的处理想要学生理解机械效率的物理含义以及计算机械效率,就必 This section of “Mechanical Efficiency” mainly includes the contents of building the concepts of useful work, extra work and total work, and understanding the two major aspects of mechanical efficiency. It is both an extension of the prior knowledge of the principles of work and work, and the basis for exploring the mechanical efficiency of bevels. Therefore, its status becomes more important. First, the concept of the three kinds of power to deal with the understanding of the need to understand the physical meaning of mechanical efficiency and computational machinery efficiency, we must