Calculate the velocity, which a spherical rain drop (whose drag coeffient is given as C = 0.45) would achieve falling to the ground from a height of 5.0 km:
(a) in the absence of air drag and,
(b) with air drag parametrized as FD=1/2CpAr² where C is the drag coefficient. A is the area of the object facing the fluid/medium (i.e. cross section), and p is the density of the fluid/medium. For the size across the drop, take it to be 4.0 mm; the mass density of water is 1.00-10 kg/m³ and the density of air is 1.21 kg/m³.
(c) Show that Fp indeed has the units of a force, and work out a reasonable estimate for the time that elapses before the rain drop effectively falls with a constant velocity.