1. The problem statement, all variables and given/known data The terminal velocity of a 2×10−5 kg raindrop is about 7m/s. Assuming a drag force Fd= - bv, Assuming a drag force determine the time required for such a drop, starting from rest, to reach 63% of terminal velocity. 2. Relevant equations Fd=-bv Sum of F-ma 3. The attempt at a solution I use Fd=-bv to solve for b then used Fd-Fg=ma and reduced that to dv/dt=-g-(bv/m) but don't know how to determine time.