In this video we finish our example on the vibration of two degree of freedom systems. We quickly go over the equations of motions, natural frequencies, and mode shapes based on what we found in the two previous tutorials. Then, we present the two time responses corresponding to the two masses of the system. We show how to use four initial conditions to find four unknowns existing in the time response expressions. Finally, these unknowns including the amplitudes and phase angles of the mode shapes are calculated using the numerical values identified for this example.