A ship travelling towards a cliff receives the echo of its whistle after 3.5 seconds. A short while later, it receives the echo after 2.5 seconds. If the speed of sound in air under the prevalling condition is 250ms -1, how much closer is the ship to the cliff?
10m
350m
175m
125m
Correct answer is D
Difference in time = 1 sec
echo time = 1 \(\div\) 2 = 0.5 sec
Difference of cliff from ship = 0.5 x 250
= 125m