Finding initial value of differential equation Given,
$$ mdv/dt = mg - kv $$
Question is:  

Find the velocity $v(t)$ that satisfies this initial value problem.
  Also, by letting $t$ approach positive infinity, determine the terminal velocity of the ball.

I first separated the equation and got
$$ dv/dt = g - k/mv $$
I have no clue how to approach this question. Can someone please help?

Set $u=g-k/m·v$. Then 
$$
u'=-\frac km ·v'=-\frac km·u
$$
which is the well known equation for exponential growth resp. decay.
