Question

A stone is dropped from a tower 100 meters above the ground. The stone falls past ground level and into a well. It hits the water at the bottom of the well 5.00 seconds after being dropped from the tower. Calculate the depth of the well. Given: g = -9.81 meters/second2.

Answer 1

Let's use the second kinematic equation, and define the depth of the well as y and 0 as the ground level.
Δy = v₀t + 1/2gt²
y-100 = 0(5) + 1/2(-9.8)(5)²
y-100 = -4.9(25) = -122.5
y = -22.5

So the well is 22.5 m deep. Make sense?