I am considering a ball that is being thrown and travelling in the air. I know that the air resistance acting on it is proportional to the difference between the velocity of the ball and the air, so say air resistance = $-k(\dot{r}- u)$.
Question - what is the value of $k$, i.e that is suitable for a ball thrown over a distance of say, around $15$ metres. I know there isn’t a universal value, but what approximate value could I use for a model. Would it have to be between $0$ and $1$?