初二物理“研究液体的压强和深度的关系”和“研究物体浮在液面的条件”两个分组实验都有向试管加沙子,并设法使试管浮于水面这一主要实验步骤。实践证明,即使教师作详细实验指导,学生在操作时仍然会出现这样或那样的问题,究其原因:一是向管里加沙子时不能掌握适当重量;二是不易调整装有沙子的管子的重 The first two physics “research on the relationship between the pressure and depth of liquids” and “research on the conditions of objects floating on the liquid surface.” Both groups of experiments have added sand to test tubes and managed to float the test tubes to the surface of the water. Practice has proved that even if the teacher makes detailed experimental guidance, students will still have problems of one kind or another in the operation. The reasons are as follows: First, they cannot grasp proper weight when sand is added to the tube; second, they are difficult to adjust the weight of the tube containing sand.