九年义务教育六年制小学第四册自然教材“力”的教学单元中,《平衡》一课的第三部分是选学内容,起测试学生智力的作用。这部分内容是:在杠杆尺一边距中心两格的位置上挂两个钩码,让学生研究有几种方法可以使杠杆达到平衡。 学生已经掌握了两种达到平衡的方法。一种是杠杆尺左右距离一样长,挂的钩码一样多,能够达到平衡;一种是左右挂钩码不一样多,杠杆尺左右的距离也不一样长,能够达到平衡。所以,学生回答上述时,在已经掌握的知识基础上能迅速答出或通过实验得出结论;在杠杆尺的另一边一样长的位置上挂两个钩码,杠杆尺达到平衡,并能在书上画出来。但另外 Among the teaching units of the “natural” textbook, the fourth volume of the six-year compulsory education in the six-year compulsory education, the third part of the lesson “Balance” consists of the contents of the election and the function of testing students' intelligence. This part is: Two hooks on the side of the lever from the center two hook code, so that students study there are several ways to balance the leverage. Students have mastered two ways to strike a balance. One is about the same length as the lever gauge, hanging as much as the hook code, to achieve balance; one is about the same hook code, the distance around the lever is not the same length, to achieve balance. Therefore, students in response to the above, based on the knowledge they have mastered can quickly answer or experimentally concluded; in the other side of the lever length of the hook hanging two hook code, lever scale to achieve balance, and in Draw on the book. But otherwise