Problem 3. The mass and stiffness of a SDOF system are 2 ks2/in. and 40 k /in., respectively. If the system is set into free vibration with the initial conditions u(0) = 0.7 in. and ů(0) = 5.6 in./s, derive expressions governing the displacement history for (a) c = 0 and (b) c = 2.8 k.s/in. Plot both responses on the same graph from t = 0 to 7 s at 0.01sec intervals. Determine the velocity of the system at t = 1.0 s in both cases.