250 kg k = 70,000 N/m 5=0.15 Q4. Consider the one degree-of-freedom model of a motorcycle suspension system as shown in Figure 1. The motorcycle has a mass 250 kg. The suspension stiffness is 70,000 N/m and the damping ratio is 0.15. The motorcycle travels over a terrain that is approximately sinusoidal with a distance between peaks of 10 m and the distance from peak to valley is 10 cm. What is the acceleration amplitude felt by the rider when the motorcycle is traveling at (a) 30 m/s; (b) 60 m/s; (c) 120 m/s? Figure 1