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《声现象》这一章中的习题第2题：“北宋时代的沈括，在他的著作《梦溪笔谈》中记载着：行军宿营，土兵枕着牛皮制的箭筒睡在地上，能及早听到夜袭的敌人的马蹄声．沈括的这段记载有什么科学道理？”第3题：“甲同学把耳朵贴在长铁管的一端，乙同学在长铁管的另一端敲一下这根
Work title #2 in the chapter “Sound Phenomenon”: “Shen Kuo in the Northern Song Dynasty recorded in his book “Meng Xi Bi Tan”: march camp, and the earthmen sleeping on the ground with a leather quiver The sound of the hoofs of the enemies who heard the night attack early. What scientific doctrine does Shen Kuo have in this paragraph?” Question 3: “A student sticks his ear to one end of the long iron tube, and student B knocks at the other end of the long iron tube. This root