Question

An echo is heard after 0.8 seconds when a person fires a cracker 125 m from a tower. Calculate the speed of sound.

Answer 1

Given:

The time taken by the echo to be heard, $t=0.8s$

Distance from the tower, $d=125m$

Finding the speed of sound (v)

When a sound after being reflected from a suitable reflecting surface is heard again after some time. Such a sound is called an echo.

We know that the distance covered by the sound is $2d$.

$$\begin{gathered} \because dis\tan ce=speed\times time \\ \Rightarrow 2d=v\times t \end{gathered}$$

By substituting the given values, we get

$$\begin{gathered} 2\times 125=v\times 0.8 \\ \Rightarrow 250=0.8v \\ \Rightarrow 312.5=v \end{gathered}$$

Hence, the speed of the sound is 312.5 m/s.