Question

A man standing between two parallel cliffs separated by a distance of 1020 m produces some sound. He hears the first echo after 2 sec and next echo after a time of ______ sec after the first echo. (V = 340m/s)

Answer 1

Answer:

4 sec

Explanation:

Assume that the man is between the two cliffs.

When he hears first echo in 2 sec, then the sound has travelled to the first cliff and then back the same distance to the man, i.e. 1 sec each to go and come back. Therefore the distance between the man and the first cliff must be (340m/s) / (1s) = 340m.

Now the distance of second cliff = 1020m - 340m = 680m

Then for the second echo the sound travels 2*680m = 1360m

So, the echo is heard after (1360m) / (340m) = 4s.

Answer 2

Answer:

2

Explanation:

Both start to travel at same time

first echo reaches at this instant the second echo touches the cliff then after 2 sec it reaches to the source .

the 2nd echo takes 4sec in total but 2 sec more than 1st echo.

So the second echo is heard 2 sec after the first