The ball. At most 45.93 g and at least 42.67 mm across — the Rules of Golf, Equipment Rules. In flight: gravity, drag, and Magnus lift from backspin, both aerodynamic forces growing with the square of airspeed.
The coefficients. Drag rising linearly with the spin ratio and lift as its 0.4 power is the form Smits & Smith found (1994, Science and Golf II). The three numbers here are fitted so one model carries a driver, 7-iron and wedge within about 3 % of the TrackMan PGA Tour averages (113 / 90 / 83 mph club speed; 2,686 / 7,097 / 9,304 rpm; 275 / 172 / 136 yd).
No dimples. A smooth sphere below its drag crisis has a drag coefficient near 0.5 (Achenbach 1972); dimples trip the boundary layer into turbulence and roughly halve it in the speed range a ball flies in (Bearman & Harvey 1976).
The ground. Green speed from the USGA Stimpmeter (a ball released at about 1.83 m/s; this green runs 11 ft). A rolling ball feels 5/7 of gravity along a slope. The cup is 108 mm; a ball dead centre drops at up to about 1.6 m/s (Holmes 1991). Wind follows a logarithmic profile with height.
Simplified. The bounce and the grass drag at speed are tuned, not measured; the putt rolls from the start without its first skid; spin decays at a fixed few per cent a second. The course is invented.