T2 - The period of the free vibration of the product on the cushion: 13.22 where - the time length or duration of the shock. For any shock of known period , we may calculate the equivalent shock frequency: 13.23 the shock duration: 13.24 13.25 2 1 2 2 = T = f 2 1 f 2 = 2 2 2 2 1 W f k g   = = k g W 2 2  = T2 - The period of the free vibration of the product on the cushion: 13.22 where - the time length or duration of the shock. For any shock of known period , we may calculate the equivalent shock frequency: 13.23 the shock duration: 13.24 13.25 2 1 2 2 = T = f 2 1 f 2 = 2 2 2 2 1 W f k g   = = k g W 2 2  = 