1. The problem statement, all variables and given/known data Initial speed = v, only for acting on it is retarding force F(v) = -Ae^(-cv). Find it's speed as a function of time. 2. Relevant equations F=ma 3. The attempt at a solution m(dv/dt) = -Ae^(-cv) dv / (-Ae^(-cv) = dt / m integrating gives [e^(-cv)/Ac] = t/m where the left side of that integral is evaluated from initial vi to final vf e^(-cvi)/Ac-e^(-cvf)/Ac = t / m multiplying by AC and taking the natural log of all of this... -cvf + cvi = ln(tAc/m) vf = vi - (1/c)*ln(tAc/m) Does this look correct? An online source says this is wrong. Thanks for the help, LaTex coming soon.