1. The problem statement, all variables and given/known data Using the viscosity of air as 1.8x10-5Pa s, and the density of water as 1x103kg m-3, find the radius of a raindrop travelling at a terminal velocity of 7.05ms-1. Assume Stokes law can be used. The problem is finding the density of air, I could use F = 6rvπη but I don't know F, because it says in a previous question to assume that in D + U = W, to assume U is negligible, and I don't know the weight, because I don't know the mass or volume of the raindrop. 2. Relevant equations r = sqrt((9ηv)/(2g(ρ-σ))) 3. The attempt at a solution Without a density of air, I get 9.31x10-5m, but that would be wrong since the density of air is not being included.