一竖直悬挂的弹簧振子原来处于静止状态,用力将振子下位0.02m后释放,使之做谐振动,并测得振动周期为0.2s,设向下为x轴的正方向,则其振动表达式(SI)为()
A campus emergency ______ occur at any time of the day or night, weekend, or holiday, with little or no warning.
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