Question

A sound signal is simultaneously sent in air and water from a boat on a river. The echo of sound striked by river bed is heard in 4s, while echo striked by aeroplane is heard in 8s. Find the distance between aeroplane and river bed [velocity of sound in air = 350m/s, velocity of sound in water =1500m/s.

1) 4.4km
2) 6.7km
3)8.8km
4)13.4km​

Answer 1

Answer:

4.4km

Explanation:

Time taken to hear echo is half the time taken to cover the distance. As for echo we have to travel twice the distance.

Distance travelled in river, sriver=vrivertriver=1500×2=3000m

Distance travelled in air, sair=vairtair=350×4=1400m

stotal=sriver+sair

=(3000+1400)m=4400m=4.4km