Question

If a stone dropped into a well reaches the water's surface after 3.0 seconds, how far did the stone drop before hitting the water?

Answer 1

Let h =  distance (m) to the water surface.

Initial velocity, u  = 0 (because the stone was dropped).
Use the formula
 h = ut + (1/2)gt^2
  where g = 9.8 m/s^2  (acc. due to graity)
              t = time (s)

h = (1/2)*(9.8)*(3^2) = 44.1 m