Separate variables in Eq. (12) and substitute u = v/g to obtain the upward-motion velocity function given in Eq. (13) with initial condition v(0) =

Separate variables in Eq. (12) and substitute u = v√ρ/g to obtain the upward-motion velocity function given in Eq. (13) with initial condition v(0) = v₀.

ap dt -g-pu = -8 (1 + 20). (12)