Abso = G w/((w0^2 - w^2)^2 + G^2 w^2)

Elas =  (w0^2 - w^2)/((w0^2 - w^2)^2 + G^2 w^2)

G = 5

w0 = 5

Plot[{Elas, Abso}, {w, 0, 10}, PlotRange -> {-.5, .5}]

Plot[Elas/Abso, {w, 0, 100}, PlotRange -> {-100, 200}]

x = Elas Cos[w t] + Abso Sin[w t]

Plot[{.2  Cos[w t] /. w -> 3, x /. w -> 3}, {t, 0, 10}]