Creates a FrictionSimulation with the given arguments, namely: the fluid drag coefficient, a unitless value; the initial position, in the same length units as used for x; and the initial velocity, in the same velocity units as used for dx.
Source
FrictionSimulation(double drag, double position, double velocity)
: _drag = drag,
_dragLog = math.log(drag),
_x = position,
_v = velocity;