Question

A stone is dropped into a deep well and is heard to hit the water 2 s after being dropped. Determine the depth of the well. Assume no time delay in stone hitting the water and sound being heard. Take
a
=
10
m
s
−
2
.

Answer 1

The distance travelled by the stone (the depth of the well) is given by the kinematic equation:

$$h = \dfrac{at^2}{2}$$

where $a =10m/s^2$ is the acceleration of the stone, and $t = 2s$ is the time.

THus, obtian:

$$h = \dfrac{10\cdot 2^2}{2} = 20m$$

Answer. 20m.