Question

The velocity of air in a planet is 500m/s. What should be the minimum distance between the source of sound and the obstacle to hear an echo?
a) 20
b) 25
c) 50
d) 17​

Answer 1

Answer:

B) 25

Explanation:

Let the distance between the source of sound and the obstacle be x metres .

Thus the distance travelled by sound to reach back to the source d=2x

As the minimum time required to hear an echo is equal to 0.1sec

Thus d=vt

2x=500(0.1)⟹x=25m

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