為什麼一個快速旋轉的陀螺不容易倒下，但一旦轉速變慢或停止就會倒下？ Why does a rapidly spinning top stay upright, but falls over once it slows down or stops?
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因為旋轉產生的角動量具有方向保持性（進動現象），能抵抗重力造成的傾斜力矩 Because the angular momentum from spinning has directional persistence (precession), resisting the tilting torque of gravity 旋轉物體擁有角動量，當外力（重力）試圖改變其旋轉軸時，會產生「進動」（Precession）而不是直接倒下，轉速夠快時就很穩定。 A spinning object possesses angular momentum. When an external force (gravity) tries to tilt the axis, it causes "precession" rather than an immediate fall. It remains stable as long as the spin is fast.