3. [20] A mass-spring-damper system has the free response shown in the figure below. a. Determine the damped natural frequency of the system. b. Determine the damping ratio of the system using the log-decrement method. c. Given that damping ratio, how close (numerically) are the damped and undamped natural frequencies? d. Determine the spring stiffness of the system if the mass is 4kg. Acceleration (g) 2 -2 0 0.01 0.02 N 0.03 0.04 0.05 Time (s) 3. [20] A mass-spring-damper system has the free response shown in the figure below. a. Determine the damped natural frequency of the system. b. Determine the damping ratio of the system using the log-decrement method. c. Given that damping ratio, how close (numerically) are the damped and undamped natural frequencies? d. Determine the spring stiffness of the system if the mass is 4kg. Acceleration (g) 2 -2 0 0.01 0.02 0.03 0.04 0.05 Time (s)