If the helicopter is going to hover in place, the force it pushes on these tiny air balls will have to be equal to the weight of the helicopter.

如果想使直升机悬停于某处，这些空气微粒的推力必须相当于直升机重量。

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The precise critical force of a system can be deduced from the fact that the determinant of stiffness matrix of the system is equal to zero in the critical condition.

由结构刚度矩阵行列式值为零的失稳条件导出结构失稳特征方程，从而精确地确定系统临界力值。

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The precise critical force of a system can be deduced from the fact that the determinant of stiffness matrix of the system is equal to zero in the critical condition.

由结构刚度矩阵行列式值为零的失稳条件导出结构失稳特征方程，从而精确地确定系统临界力值。

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