升力能够抵消鸟儿自身的重力,使鸟儿停留在空中。可是,升力看不见、摸不着,怎样感受它的存在呢?你需要:一张纸,一把尺子和一把剪刀。第一步:用尺子量出一张长15厘米、宽5厘米的纸条,用剪刀剪下来。第二步:用拇指和食指轻轻捏住纸条的一端。第三步:用另一只手的拇指和食 Lift can counteract the bird’s own weight and keep the bird in the air. However, the lift can not see, touch, how to feel its existence? You need: a piece of paper, a ruler and a pair of scissors. The first step: using a ruler to measure a length of 15 cm, width 5 cm of paper, cut with scissors. Step two: gently pinch the end of the note with your thumb and index finger. The third step: with the other hand’s thumb and food