Help with B

Problem 7 (Pollen grain) Pollen grains are very light and roughly the shape of a sphere. To study the drift of pollen, researchers dropped grains of pollen inside a cylinder of still air to compare the rate they fell to that of a sphere. A. Since pollen grains are very small and travel at low speeds, their Reynolds number is very small. The drag force Fa is then proportional to: a. Fa