if we assume the origin is at the dropping point and the object is merely dropped and not thrown up or down then y0 = 0 and v0 = 0. The equation reduces to
y = 0 + 0t + ½gt²
y = ½gt²
t = √(2y/g)
in the ft - lb - s system
y = -100 ft
g = -32.2 ft / s²
t = √(2y/g)
t = √(2(-100) / (-32.2))
t = 2.5 s
