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在现行教材《飞机是怎样飞行的》一课中,多次提到“升力”这个概念。按课本的叙述理解,这里的“升力”是指使气球(包括氢气球、氦气球和热空气球)、风筝、飞机上升的力。倘若仔细地分析,这三种情况下的“升力”却不尽相同。试述如下: 一、气球的升力 气球,不管是氢气球,氦气球还是热空气球,其共同点就是气球内装的气体比空气轻,即它们的密度比空气密度小。
In the course of the current textbook, “How Airplanes Fly,” the concept of “lift” was mentioned many times. According to the narrative of the textbook, “lift” here refers to the force that makes balloons (including hydrogen balloons, helium balloons, and hot air balloons), kites, and planes rise. If we analyze carefully, the “lift” in these three cases is not the same. The following are the descriptions: 1. Balloon Lifting Balloons, whether they are hydrogen balloons, helium balloons or hot air balloons, have in common that the gas contained in the balloons is lighter than air, that is, their density is lower than air density.