So let me get this straight.
If you consider the distance as the Δd, then you cannot consider the distance as d for a non-constant velocity (i.e. there is acceleration)?
I guess this leads to a very interesting question (and probably the source of my confusion). In the equation [tex]v = d/t[/tex], what is the d stand for, physically? It surely cannot be the height; the height is Δd, right?