A stone falls from the top of a 125m high cliff.How long does it take to reach the sea?I know that S[distance] is 125m, and that A[acceleration] is 10m/s². Considering the equations of motion- I can find the answer only if I receive another piece of information as final velocity, or initial velocity. 

V1 = initial velocity = 0 ( fall = dropped= from rest )S = V1*t + 1/2 *g*t^2125 = 0 +  1/2 *10 t^2 = 5 t^2>>>>>>>>>>>>t^2 = 125/5 = 25 t = sqrt 25 = 5 secV2 = final velocity = V11 + gt = 0 + 10 * 5 = 50m/s

The initial velocity is 0 since it isn't moving at the beginning.0=-10t^2+12510t^2=125t^2=12.5t≈3.53553391 seconds