A Rocket R is fired from ground with inital speed s to the horizontal at an angle $\displaystyle \alpha$. There is a resistive force F=-mkv where m is the mass and v is the vector (v1,v2) and K is a constant. Show the equations of motion are

$\displaystyle d/dt(v1)+kv1=0$ and $\displaystyle d/dt(v2)+kv2= -g$

My answer. First in the horizontal direction there is no resultant force so I don't get it