Problem 4 (10 pts) Part of a -periodic forcing function f(t) = |sin(t)| N is shown in Fig.4. Obtain the Fourier series expansion of that forcing function. 1.0 0.8 0.6 0.4 0.2 f(t) MM 2 4 6 8 Figure 4 t 10 12 10 Problem 5 (9 + 6 = 15 pts) The periodic forcing in problem 4 is applied to a SDOF mass-spring-damper system shown in Fig.5. The system parameters are m = 1kg, b = 0.16 N. s/m and k = 64 N/m. == a) Determine the forced response x(t) of the system. b) Plot/sketch amplitude spectra for both f(t) and x(t). Which harmonics are dominant in f(t) and x(t)? f k m x Figure 5