model PlanarPend
  Real x,y,vx,vy,Fx,Fy;
  Real x1,x2,y1,y2,Fx1,Fx2,Fy1,Fy2,F,th(start=-0.5),w;
  Real Fxg,Fyg;
  parameter Real m=1,L=1,g=9.8;
equation
  der(x)=vx;
  der(y)=vy;
  m*der(vx)=Fx;
  m*der(vy)=Fy;
  Fxg=0;
  Fyg=-m*g;
  L*sin(th)=x2-x1;
  L*cos(th)=y2-y1;
  Fx1=F*sin(th);
  Fy1=F*cos(th);
  Fx1+Fx2=0;
  Fy1+Fy2=0;
  der(th)=w;
  x1=0;
  y1=0;
  x2=x;
  y2=y;
  Fx+Fx2+Fxg=0;
  Fy+Fy2+Fyg=0;
end PlanarPend;