Conservation of Angular Momentum
Core Sentence / 核心句
Angular momentum about a chosen axis is conserved when the net external torque about that axis is zero.
Watch Out / 易错点
zero external force 不是必要条件；要检查 external torque。角动量守恒也不保证机械能守恒。
Angular momentum about a chosen axis is conserved when the net external torque about that axis is zero.
zero external force 不是必要条件；要检查 external torque。角动量守恒也不保证机械能守恒。