Consider the single-degree-of-freedom system shown in Figure 9.8. The excitation force due to the rotating unbalance is meω2sin(ωt). Assume that the system has the following parameters: m = 5 kg, M = 100 kg, e = 0.1 m, k = 5,000 N/m, and b = 200 N・s/m.
a. Determine the force transmitted to the support when the system runs at the rotating speed ω = 1.5ωn.
b. Determine the force transmissibility.
c. The spring is replaced to decrease the force transmissibility at the same excitation
frequency to 20%. Determine the stiffness of the new spring.