Question

A student standing in front of a huge building claps his hands. He heard its echo after 2 seconds (Speed of sound in air is 340 m/sec). Calculate the distance between the student and the building.

Answer 1

Hint: In this question we have been asked to calculate the distance between the student and the building. It is given that the student clapped his hands and heard an echo after 2 seconds. Therefore, to solve this question, we shall first calculate the total distance traveled by the sound before reaching the ears of the student. We have been given the speed of sound. We know that speed is given as distance covered over time. Therefore, using this we can calculate the distance between students and buildings.

Complete step-by-step solution
Let us assume that the student is standing at a distance ‘x’ from the building as shown in the figure below.

Now, we can say that when the student clapped his hands the sound wave will hit the wall and reflect back to the student after two seconds. Therefore, the total distance covered by the sound wave will be twice the distance ‘x’.
Therefore,
Distance \[d=2x\]
It is given that, time \[t=2s\]
The speed of sound \[s=340m/s\]
Now, we know that,
\[s=\dfrac{d}{t}\]
After substituting values
We get,
\[340=\dfrac{2x}{2}\]
Therefore,
\[x=340m\]
Therefore, the distance between the student and building is 340 meters.

Note: The echo is a phenomenon where the sound generated by a source is heard again at the source after reflecting from a distant object such as a building or mountain. This sound is heard after some time. The delay in listening to the sound is directly proportional to the distance between the listener and the reflecting surface.