Question

Sound moves at 345m/sec towards a rock wall, reflects and returns as an echo. The roundtrip takes 2 sec.

How far away is the wall?​

Answer 1

SOLUTION

GIVEN

• Sound moves at 345m/sec towards a rock wall, reflects and returns as an echo.

• The roundtrip takes 2 sec.

TO DETERMINE

How far away is the wall

EVALUATION

Here it is given that

Sound moves at 345 m/sec towards a rock wall

∴ Speed of sound = 345 m/sec

Now the sound reflects and returns as an echo.

The roundtrip takes 2 sec.

So Distance travelled by the sound

= ( 345 × 2 ) metre

= 690 metre

Now in 2 sec sound has travelled twice the distance between the wall and the source

Hence the distance between the wall and the source

$\displaystyle\sf{ = \frac{690}{2} \: \: metre }$

$\displaystyle\sf{ = 345 \: \: metre }$

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Answer 2

Explanation:

So Distance travelled by the sound

= ( 345 × 2 ) metre

= 690 metre

Now in 2 sec sound has travelled twice the distance between the wall and the source

Hence the distance between the wall and the source

\displaystyle\sf{ = \frac{690}{2} \: \: metre }=

2

690

metre

\displaystyle\sf{ = 345 \: \: metre }=345metre

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