Three guys are standing in a row, facing a solid, high wall. Guy A is 10 m from the wall, B is 20 m away from the wall, and C is 30 m away from it. Guy B shouts. Will any other guy be able to hear an echo of Guy B’s shout?

Only guy B and C will be able to hear the echo but guy A  will not be able to hear the echo

Explanation:

Given that:

Guy A  = 10 m away from the wall

Guy B = 20 m away from the wall

Guy C = 30 m away from the wall

At standard Temperature of 20 °C, velocity of sound in dry air ≅ 343 m/s. As such, if there is a reflecting object that produces an echo, it mustn't be more than 17.2 m from where the sound is originating from. As the sound is coming from guy B who is 20 m away, only Guy B and C who are above 17.2 m will only perceive the  echo.

d eras and periods

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explanation:

physics means: "the branch of science concerned with the nature and properties of matter and energy. the subject matter of physics, distinguished from that of chemistry and biology, includes mechanics, heat, light and other radiation, sound, electricity, magnetism, and the structure of atoms."