“简单机械”、“功和能”是初中物理中的重要内容。在实际应用中,这两部分内容往往是紧密结合在一起的.譬如机械效率的计算问题就是如此。有关机械效率的计算题,很多同学都感到困难,特别对计算几种简单机械联合装置的效率问题,更是棘手。其实如果掌握了解题的关键,解答起来并不难。那么解题的关键是什么呢?我认为有下面几点: “Simple mechanics,” “work and energy,” are important aspects of junior high school physics. In practical applications, the two parts are often closely combined, such as the calculation of mechanical efficiency. With regard to the calculation of mechanical efficiency, many students find it difficult, especially for the calculation of the efficiency of several simple mechanical devices. In fact, if you master the key to understanding the problem, it is not difficult to answer it. So what is the key to problem solving? I think there are the following points: