Aspring-damper system is designed to support an electric motor which has a total mass of 20 kg and an unknown rotating imbalance. in free vibration, a displacement of 16 mm is damped to 1 mm in two cycles. determine the required spring stiffness so that only 20% of the vertical component of the unbalanced force is transmitted to the ground when the motor is running at 1,200 rpm, assuming the damping ratio remains constant.