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ICSE Class 10 Physics Question 23 of 27

Solved Sample Paper 3 — Question 11

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Question 7(ii)

A student stands 330 m from a tall cliff which is 990 m from another tall cliff.

A student stands 330 m from a tall cliff which is 990 m from another tall cliff. The student fires a pistol and hears some echoes. If the speed of sound between the cliffs is 330 m/s, What is the time taken by first echo to reach the student? Find the time interval between the first echo and the second echo. Physics Sample Paper Solved ICSE Class 10.

The student fires a pistol and hears some echoes. If the speed of sound between the cliffs is 330 m/s,

(a) What is the time taken by first echo to reach the student?

(b) Find the time interval between the first echo and the second echo.

Answer

(a) Given,

D1 = 330 m

D2 = 660 m

V = 330 ms-1

t1 = ?

t2 = ?

As we know,

Time interval (t)1=Total distance travelled (2d)Speed of sound (V)\text {Time interval (t)}_1 = \dfrac{\text{Total distance travelled (2d)}}{\text {Speed of sound (V)}} \\[0.5em]

t1=2×330330⇒t1=2s\text{t}_1 = \dfrac{2 \times 330 }{330} \\[0.5em] \Rightarrow \text{t}_1 = 2 \text{s}

Hence, time taken by first echo to reach the student = 2 s

(b) time taken by second echo to reach the student :

t2=2×660330⇒t2=4s\text{t}_2 = \dfrac{2 \times 660 }{330} \\[0.5em] \Rightarrow \text{t}_2 = 4 \text{s}

t2 - t1 = 4 - 2 = 2 s

Hence, time interval between two echoes is 2 s