model ClassicGravitation
  parameter Real    G=6.674e-11 "Gravitational Constant";
  Real              m1    "mass #1";
  Real              m2    "mass #2";
  Real              r     "radius";
  Real              F     "force";
equation
  F = (G * m1 * m2) / (r^2)
end ClassicGravitation;