h = v₀t + qt²/2
v₀t = h - qt²/2
v₀ = (h - qt²/2)/h
gt²/2 = h - v₀t
g = 2(h - v₀t)/t²
5/9 = 2/5
2/5 = 8
8×3 < 8 - 6 < 9 × 3