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课本上的练习题或飞题可以在考试题中以变通或加深的新形式出现,现对九年制义务教育初二物理159页五题作如下变换:原题目用一块塑料片挡住两端开口的玻璃筒下端,竖直地插入水中(如图一),塑料片为什么不下沉?向玻璃筒内缓慢倒水,注意观察筒内水面多高时塑料片下沉,并说明原因。由于塑料片受到水对它的向上压强作用,使
Textbook exercises or flying questions can appear in the test questions in a new form of adaptation or intensification. Now the five questions of the ninth-year compulsory education day two physics 159 pages are changed as follows: The original title blocks the two ends with a piece of plastic. The bottom of the glass tube is inserted into the water vertically (as shown in Fig. 1). Why doesn’t the plastic sheet sink? Slowly pour the water into the glass tube. Observe how high the water level in the tube is when the plastic sheet sinks, and explain why. As the plastic sheet is subjected to its upward pressure on water,