MP Board · Class 9 · Science · SoundA SONAR device fitted on a submarine sends out an ultrasonic signal that returns from an underwater rock after $2.4\text{ seconds}$. If the speed of sound in seawater is $1500\text{ m/s}$, calculate the distance of the rock from the submarine.

Given:

• Time taken for the signal to return ($t$) = $2.4\text{ s}$
• Speed of sound in seawater ($v$) = $1500\text{ m/s}$

Formula:\nLet the distance between the submarine and the rock be $d$.\nThe total distance covered by the ultrasonic signal going and returning = $2d$. $$\text{Speed } (v) = \frac{\text{Total distance}}{\text{Time}} = \frac{2d}{t}$$

Step-by-step Calculation: $$2d = v \times t$$ $$2d = 1500\text{ m/s} \times 2.4\text{ s}$$ $$2d = 3600\text{ m}$$ $$d = \frac{3600}{2} = 1800\text{ m}$$

Answer:\nThe distance of the rock from the submarine is $1800\text{ m}$ (or $1.8\text{ km}$).