A man standing between two parallel hills fires a gun and hears two echoes, one 2.5 s and the other 3.5 s after the firing. If the velocity of sound is 330 ms-1, how long will it take him to hear the third echo?

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Q: 4 (NDA-I/2008)
A man standing between two parallel hills fires a gun and hears two echoes, one
2.5 s and the other
3.5 s after the firing. If the velocity of sound is 330 ms-1, how long will it take him to hear the third echo?

question_subject: 

Science

question_exam: 

NDA-I

stats: 

0,9,16,4,11,9,1

keywords: 

{'third echo': [0, 0, 1, 0], 'velocity': [0, 2, 2, 6], 'echoes': [0, 0, 1, 0], 'sound': [4, 3, 10, 15], 'parallel hills': [0, 0, 1, 0], 'firing': [0, 0, 1, 0], 'gun': [0, 1, 1, 1]}

The correct answer is option 3: 6 s.

In this scenario, the man is standing between two parallel hills and fires a gun. He hears two echoes, one 2.5 seconds after the firing and the other 3.5 seconds after the firing.

To understand why it will take 6 seconds to hear the third echo, let`s break it down:

- The first echo is heard after 2.5 seconds. This means that the sound wave traveled from the man to the hill and back in 2.5 seconds.

- The second echo is heard after 3.5 seconds. This means that the sound wave traveled from the man to the other hill and back in 3.5 seconds.

Since the two hills are parallel, the distance from the man to each hill is the same. Therefore, the time it takes for the sound to travel from the man to each hill is equal.

To find the time it takes for the sound to travel from the man to the hill and back (one round trip), we can subtract the time it takes for the sound to travel from the man to the hill.

So, the time it takes for the sound to travel from the man to each hill and back will be (3.5