SpringDescription.withDampingRatio({double mass, double springConstant, double ratio: 1.0 })

Creates a spring given the mass (m), spring constant (k), and damping ratio (ΞΆ). The damping ratio is especially useful trying to determing the type of spring to create. A ratio of 1.0 creates a critically damped spring, > 1.0 creates an overdamped spring and < 1.0 an underdamped one.

See mass and springConstant for the units for those arguments. The damping ratio is unitless.

Source 

SpringDescription.withDampingRatio({
  double mass,
  double springConstant,
  double ratio: 1.0
}) : mass = mass,
     springConstant = springConstant,
     damping = ratio * 2.0 * math.sqrt(mass * springConstant);