(4) Figure 4.3 is a spring-mass system sliding on a dry surface. The system is imparted with an initial displacement (x0) at a time of 0 seconds (t=0 s) and a zero initial velocity (v0=0 m/s ). The static coefficient of friction is s and k is the coefficient of kinetic (sliding) friction. System Parameters: - k1=25N/m - k2=75N/m - m=25kg - s=0.06 - k=0.05 - x(t=0)=x0=2m - x(t=0)=v0=0m/s (a) Determine the equivalent spring stiffness (keq) for the system (b) Calculate the number of half cycles (n) until the oscillations of the system stop