We considered projectile motion -- an idealized motion of an object through the air that is subject to the force of gravity but not resistance. The upshot is that the motion can be described by two components: a horizontal component that has zero acceleration (hence has a constant velocity) and a vertical component that has a constant acceleration, namely the acceleration due to gravity of -9.8 m/s² (assuming vertically upward is the positive direction).

We imagined looking at the motion from an "eye in the sky" perspective in which the motion seemed to be purely horizontal (and at constant velocity) as well as looking at the motion from directly in front the path in which the motion seemed to be purely vertical (and at constant acceleration). Furthermore, we considered the situation of dropping something on an airplane that had reached a cruising speed. In the "frame of reference" of the plane the object seems only to fall vertically with no horizontal component whatsoever. On the other hand, in a cloud's frame of reference the object has both horizontal and vertical parts -- with the horizontal part matching the cruising velocity of the plane and the vertical consistent with one-dimensional falling.

We looked at a situation of shooting a projectile horizontally from a height h and it hitting the "ground" a distance R away.  Using the vertical equations, we could establish the time of flight as 

t = (2 h / g)^1/2

Using the horizontal equations, we found a result for the speed

v = R (g / (2 h))^1/2