For positive constants $k$ and $g$, the velocity, $v$, of a particle of mass $m$ at time $t$ is given by $$v=\frac{mg}{k}\left(1-e^{-kt/m}\right).$$ At what rate is the velocity is changing at time 0? At $t=2$? What do your answers tell you about the motion?

At what rate is the velocity changing at time 0?
rate =
At what rate is it changing at $t = 2$?
rate =

(What do your answers tell you about the motion of the particle?)