Question

A person hears his sound again after reflection from obstacle situated far away after 2.5 seconds. If velocity of sound is taken to be 330m/s, how far is the obstacle away from him? *

Answer 1

The person hears the reflected sound after 2.5 seconds of producing it. The distance travelled by the sound during this time is equal to twice the distance between the person and the obstacle.

Because the sound reaches the obstacle and gets reflected back to the person, thereby travelling the distance between them two time.

Let the distance between the person and the obstacle be $\sf{d.}$ So we know that,

$\longrightarrow\sf{Distance=Speed\times Time}$

Here,

• Distance $\sf{=2d}$

• Speed $\sf{=330\ m\ s^{-1}}$

• Time $\sf{=2.5\ s}$

Hence,

$\longrightarrow\sf{2d=330\times2.5}$

$\longrightarrow\sf{2d=825}$

$\longrightarrow\sf{\underline{\underline{d=412.5\ m}}}$