匀质圆盘半径为R,质量为m,沿斜面作纯滚动。已知轮心加速度为a,则圆盘个质点的惯性力向O点简化的结果是:惯性力系主矩MQO的大小等于( )。
A campus emergency ______ occur at any time of the day or night, weekend, or holiday, with little or no warning.
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