Question

A sound pulse sent vertically downward into the earth is reflected from two different ways of the earth such that echoes are heard after 1.25s and 1.45s, assuming the speed of the pulse is 200ms-1 calculate the distance between the lattes?

Answer 1

pulse 1 goes outbound for 1.25/2 = .650 seconds
pulse 2 goes outbound for 1.45/2 = .725 seconds
difference in one way time = .725 - .650 = .075 seconds
so
difference in range = 200 m/s * .075 s = 15 meters

Answer 2

the 2nd echo is 200 ms behind the 1st
... 100 ms out and 100 ms back

200 m/s * 100 ms = ? m

Answer 3

Using: V= 2x/t..
x1= 200* 1.25/2 = 125 m
x2= 200* 1.45/2= 145 m.
Distance between the layers = x2 - x1 = (145 - 125) m
= 20 metres.