Problem 4. (30 pts) Determine the amplitudes of motion of the three masses when a harmonic force is applied to the lower left mass with m = 1 kg, k = 1000 N/m, Fo = 1000 N/m, Fo = 5 N, F(t) = Fo sin wt and w = 10 rad/s using the mode superposition method. k 000 k 2m k 000 m m F(t)