一弹簧振子,重物的质量为m,弹簧的倔强系数为k,该振子作振幅为A的简谐振动,当重物通过平衡位置且向规定的正方向运动时,开始计时,则其振动方程为
A campus emergency ______ occur at any time of the day or night, weekend, or holiday, with little or no warning.
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