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Classical Mechanics Level 2

A man claps his hands near a mountain and hears the echo after 4 seconds. Let the speed of sound in air be 1188 k m h − 1 km h^{-1} . Find the distance of the man from the mountain in meters.


The answer is 660.

Mehul Arora by Mehul Arora , 20, India

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3 solutions

Hello and peace be upon you,

as for the distance for an echo,

d = (v.t )/ 2 = [ [( 1188 x 1000 ) / 3600 ] x 4 ] / 2 = 660 m...

thanks.....

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Good solution. I like the way you solved my question!!

The highlight of your solution is the first line.

Keep up the good work!!

Mehul Arora - 6 years, 5 months ago

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I'm glad, you are happy, thanks...

MOHD NAIM MOHD AMIN - 6 years, 5 months ago
Ashish Menon
May 28, 2016

1188 k m / h = 1188 × 5 18 = 66 × 5 m / s 1188 km/h = 1188 × \dfrac{5}{18} = 66 × 5m/s .
Now, distance travelled by echo = 2×distance between mountain and observer.
So, 66 × 5 = 2 d 4 d = 66 × 5 × 2 d = 660 m 66 × 5 = \dfrac{2d}{4}\\ d = 66 × 5 × 2\\ d = \color{#69047E}{\boxed{660 m}}

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Himanshu Sharma
Dec 29, 2014

Simple question.

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