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ICSE Class 9 Physics Question 15 of 19

Propagation of Sound Waves — Question 11

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Question

Question 11

Assuming the speed of sound in air equal to 340 m s-1 and in water equal to 1360 m s-1 , find the time taken to travel a distance 1700 m by sound in (i) air and (ii) water.

Answer

(i) Given,

Speed of sound in air (Va) = 340 m s-1

Speed of sound in water (Vw) = 1360 m s-1

Distance (d) = 1700 m

t = ?

V = Distance (d)Time (t)\dfrac{\text{Distance (d)}}{\text {Time (t)}}

Substituting the values for air, we get,

340=1700t⇒t=1700340⇒t=5 s340 = \dfrac{1700}{\text t} \\[0.5em] \Rightarrow \text t = \dfrac{1700}{340} \\[0.5em] \Rightarrow \text t = 5 \text { s} \\[0.5em]

Therefore, the time taken by sound to travel in air = 5 s

(ii) Substituting the values for water, we get,

1360=1700t⇒t=17001360⇒t=1.25 s1360 = \dfrac{1700}{\text t} \\[0.5em] \Rightarrow \text t = \dfrac{1700}{1360} \\[0.5em] \Rightarrow \text t = 1.25 \text { s} \\[0.5em]

Therefore, the time taken by sound to travel in air = 1.25 s