You drop a stone down a well that is 9.5 m deep.How long is it before you hear the splash? The speed of sound in air is 343 m/s and air resistance is negligible.
A)1.2 s
B)1.3 s
C)1.4 s
D)1.5 s
E)1.6 s

Question

Quizplus · Accepted Answer

The total time it takes for the stone to fall and for its sound to reach the surface would be:

time = time to fall + time for sound to travel up

time to fall = sqrt(2d/g) where d is the depth of the well and g is acceleration due to gravity (approx. 9.8 m/s^2). 
Substituting the values, we get:
time to fall = sqrt(2*9.5/9.8) ≈1.37 s

time for sound to travel up = distance/speed of sound
This distance is the same as the depth of the well = 9.5 m
Substituting the speed of sound, we get:
time for sound to travel up = 9.5/343 ≈ 0.028 s

Adding the two times, we get:
total time = 1.37 + 0.028 ≈ 1.4 s

Therefore, the best choice is C) 1.4 s.

You Drop a Stone Down a Well That Is 9