简单机械作为重要的考查内容之一,主要有杠杆和滑轮两大类,本章内容概念较多,综合性强,既是初中的难点又是重点,但同学们在解这类题时往往出错,现就几例加以解析: As one of the important contents of investigation, simple machinery mainly consists of two categories: levers and pulleys. This chapter has many concepts and comprehensive features. It is both a difficult and a key point for junior high schools, but students often make mistakes in solving such problems. For a few cases to be resolved: