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液体的压强是初中物理教学中的难点之一.初二学生从“液体的压强”演示实验中,直观的感受到液体压强的规律,又从“液体压强的计算”中学到了液体压强的定量关系.学生能运用p=ρgh进行有关的简单计算,但解释有关的问题就难了.学生往往把容器底部受到的压力跟容器中液体所受的重力混为一谈,把液体的压强跟容器的底面积相联系.如图1所示:学生难以理解水对茶杯底的压力小于杯内水所受的重力.究其原因,是学生对p=ρgh的物理意义不理解,只是死背硬记套公式.笔者在教学实践中,依据教学大纲,挖掘教材潜力,设计并制作了能演示“液体的压强只跟液体的密度和液体的深度有关系,而与液体所受的重力、容器的形状无关”的教具,在课堂教学中收到良好的效果.现将制做工艺和演示过程介绍如下:
The pressure of liquid is one of the difficulties in junior high school physics teaching. The second grader learned the law of liquid pressure intuitively from the “liquid pressure” demonstration experiment, and learned the quantitative relationship of liquid pressure from the “calculation of liquid pressure”. Students can use p=ρgh for simple calculations, but it is difficult to explain the problem. Students tend to confuse the pressure at the bottom of the container with the gravity of the liquid in the container, and the pressure of the liquid is compared with the bottom area of the container. Contact. As shown in Figure 1, students find it difficult to understand that the pressure of water on the bottom of the cup is less than the gravity of the water in the cup. The reason is that students do not understand the physical meaning of p=ρgh, but it is just a hard-booking formula. In the teaching practice, according to the syllabus, the author taps the potential of the textbook and designs and produces a demonstration that “the pressure of a liquid is only related to the density of the liquid and the depth of the liquid, but not to the gravity of the liquid or the shape of the container”. Teaching aids have received good results in classroom teaching. Now we will introduce the manufacturing process and presentation process as follows: