yea i haven't done this crap in so long, I'm trying to remember it.

i think the units are important in this.

Newtons are kg*m/s<sup>2</sup>

velocity is m/s

so the force of air resistance = (-100)(kg*m/s<sup>2</sup>)(s<sup>2</sup>/m<sup>2</sup>)(m<sup>2</sup>/s<sup>2</sup>) = -100 kg*m/s<sup>2</sup> = -100 N

so the air friction force is constant, which means your equation is simply 999890 N = 100 kg dv/dt

which is the same as 9998.9 m/s<sup>2</sup>=dv/dt

so then dv = 9998.9 m/s<sup>2</sup> dt

so v = 9998.9 m/s<sup>2</sup> * t