An unbalanced engine mounted on an elastic support imposes a periodic vertical force on the support at the rotational frequency of the engine. In order to determine the relationship between the engine rotational frequency and the resonance frequency of the elastically supported engine, the engine run speed was slowly increased from its normal value of 400 rpm to 480 rpm, which resulted in a trebling of the amplitude of the measured displacement. No resonance was observed in the displacement response in the range of speeds investigated. Assuming that the damping present in the existing elastic support is negligible, determine: The natural frequency of the elastically supported engine rad/s. Your answer should be accurate to +/-0.1. It is proposed to reduce the vibration displacement amplitude at the normal run speed of 400 rpm to 80 % of its current value by inserting a damping device. The required damping ratio of the device is_ Your answer should be accurate to +/-0.01. If the mass of the machine is 600 kg, the damping coefficient of the damping device is Your answer should be accurate to +/- 1. kNs/m.