Consider the motion of an object in a spring-mass system with damping, under the influence of a periodic forcing function $F(t)=F_0\cos(\omega t)$, so that the equation of motion is $$my''+cy'+ky = F_0\cos(\omega t).$$
With the following simulation you can analyse the motion of an object in a spring–mass system with damping, subject to an external force $F(t)=F_0\cos(\omega t)$. The simulation also displays the solution of the initial value problem $$m y''+cy'+ky=F_0\cos(\omega t),\quad y(0)=y_0,\quad y'(0)=v_0.$$
Things to try:
Note: $\omega_0=\sqrt{k/m}$.