A square platform PQRS and a car that it is supporting have a combined mass of M. The platform is suspended by four elastic wires from a fixed point O, as indicated in Fig. 2.72. The vertical distance between the point of suspension O and the horizontal equilibrium position of the platform is h. If the side of the platform is a and the stiffness of each wire is k, determine the period of vertical vibration of the platform.
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