Walker, Halliday & Resnick — Force and Motion-II: Problem 36

36 A water droplet 4.0 mm in diameter is falling with a speed of 10 km/h at an altitude of 20 km. Another droplet 6.0 mm in diameter is falling at 25% of that speed and at 25% of that altitude. The density of air at 20 km is 0.20 kg/m³ and that at 5.0 km is 0.70 kg/m³. Assume that the drag coefficient C is the same for the two drops. Find the ratio of the drag force on the higher drop to that on the lower drop.