机械效率是有用功与总功的比值,是表示一个机械的性能好坏的指标之一。机械效率越大,机械的性能越好,就越能充分地发挥机械设备的作用。寻找提高机械效率的方法具有重要的经济意义,可以减少能耗,降低生产成本。滑轮组的机械效率类试题是中考热点,会使学生出现许多错误。学生在这类问题中常犯的错误大致有以下两类。例1如图1所示,物体G在拉力F的作用下作匀速直线运动,拉力所做的功是600J,物体向左移动了2m, Mechanical efficiency is the ratio of useful work and total work is one of the indicators of the performance of a mechanical performance. The greater the mechanical efficiency, the better the mechanical properties, the more fully play the role of mechanical equipment. Finding ways to improve mechanical efficiency has important economic implications, reducing energy consumption and lowering production costs. Pulley group mechanical efficiency class test is a hot test, students will make many mistakes. Students often make mistakes in such problems in the following two categories. Example 1 As shown in Figure 1, the object G under the action of pulling force F for uniform linear motion, the pulling force is 600J, the object moved to the left 2m,