To control the vibration of a 1DOF oscillator consisted of mass m = 100 kg and spring k = 10 kN/m, a detuner is used. It is known that the mass of the detuner m = 30 kg. Determining the stiffness of the detuner spring k for the following excitation conditions: Case 1: periodic force applied on m at 5 Hz; Case 2: impact force applied on m. Hint: impact force excites the vibration at resonance frequency. F k m m V.x