An echo is returned in 3 s.
Question.
An echo is returned in $3 \mathrm{~s}$. What is the distance of the reflecting surface from the source, given that the speed of sound is $342 \mathrm{~ms}^{-1}$ ?

Solution:

Given, speed of sound, $\mathrm{v}=342 \mathrm{~m} \mathrm{~s}^{-1}$;

time taken for hearing the echo, $\mathrm{t}=3 \mathrm{~s}$;

distance of the reflecting surface, $\mathrm{s}=$ ?

Now, $\mathrm{s}=\frac{\mathrm{v}}{2}=\frac{342}{2}=\mathbf{5 1 3} \mathbf{~ m}$
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