2.130 The free-vibration responses of an electric motor of weight 500 N mounted on different types of foundations are shown in Figs. 2.114(a) and (b). Identify the following in each case: (i) the nature of damping provided by the foundation, (ii) the spring constant and damping coeffi- cient of the foundation, and (iii) the undamped and damped natural frequencies of the electric motor. x(t), mm Mas 0.1 0.2 0.3 0.4 0.5 0.6 8 0 x(t), mm 8 0.1 6 (a) 0.2 0.3 0.4 (b) 0.5 t, s t, s​