A flower pot is accidently knocked off a window ledge and falls 30.625 meters . How long does it take to reach the groound.

a = -g = -9.81 m/s^2

v = a t = -9.81 t
height = Initial height + initial velocity * t + (1/2) a t^2
0 = 30.625 + 0 * t - 4.9 t^2
so
t^2 = 30.625 / 4.9
t = 2.5 seconds