垂直放置的矩形挡水平板,深为3m,如果矩形面积为3m2,则矩形所受的静水总压力为( )
A campus emergency ______ occur at any time of the day or night, weekend, or holiday, with little or no warning.
垂直放置的矩形平板,一侧挡水,该平板由置于上、下边缘的拉杆固定,则拉力之比T1/T2应为()
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