Hi, why is it that as the frequency of the driver decreases below the natural frequency of the oscillator it reaches a fixed amplitude when the external frequency is zero whereas whenever you go to the other extreme and have a very high external frequency the amplitude of the oscillator approaches zero? The graph that displays this information shows that the amplitude of the oscillator has a value (Fo/k) when the driving frequency is zero (i.e. the graph doesn't go through the origin). How can you have an amplitude at zero frequency? Thanks for any help given!