x(t) = v0xt, (2)
where v0x denotes the initial velocity in the x-direction.
As equation (2) shows, the projectile is not accelerated in the x-direction
and thus will not change its velocity according to Newton’s first law.
Note that both equations can be treated independently, but what we eventually observe
is the superposition of both types of motion, E r(t) = (x(t), y(t)).