当我们把一只猫四脚朝天抓住如(图2),然后让它从静止自由落下,我们发现这只猫不是背部着地而是在空中使身体翻转过来,最后四脚着地。猫在开始跌落的瞬间,它的角动量为零而能在空中转体,这似乎违背了角动量守恒定律,其实不然。因为角动量为零的物体不一 When we grabbed a cat all the way to the sky (Figure 2) and let it free fall, we found that the cat flipped over in the air instead of the back, with the last four legs on the ground. At the moment the cat begins to fall, its angular momentum is zero and can swivel in the air, which seems contrary to the law of conservation of angular momentum, but it is not. Because of the angular momentum of zero objects