Change u as the model runs: u =

tmax=10; InitGraph(); ScaleWindow(0,-40,tmax,40); DrawAxes(); Label('Second order example',1,35); x=10; //Initial values v=-.1 Colour(Black); t=0; LineStart(t,x); StepModel();
//function StepModel() v = v + u * dt; x = x + v * dt; t = t + dt; LineTo(t, x); if (t<tmax){ setTimeout('StepModel()',40); }