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Solved 2025 Question Paper ICSE Class 10 Physics — Question 11

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11
Question

Question 7(ii)

A submarine in the sea, sends ultrasonic ping and a stopwatch is started simultaneously. The stopwatch stops on receiving the reflected wave from an obstacle and reads 1 minute 40 seconds. Calculate the distance of the obstacle from the submarine (Speed of sound in water 1500 ms-1)

Answer

Given,

Time taken = 1 minute 40 seconds = 100 s

Speed of sound = 1500 ms-1)

So,

Distance of the obstacle=Speed of sound×Time taken2=1500×1002=1500002=75000 m=75 km\text {Distance of the obstacle} = \dfrac {\text {Speed of sound} \times \text {Time taken}}{2} \\[1em] =\dfrac{1500 \times 100}{2} = \dfrac{150000}{2} \\[1em] = 75000\ \text m = 75\ \text {km}