A person, with his ear to the ground, sees a huge stone strike the concrete pavement. A moment later two sounds are heard from the impact: one travels in the air and the other in the concrete, and they are 0.75 s apart. How far away did the impact occur?
The velocity of sound through the indicated mediums are as follows:
v_air(20°C) = 343 m/s
v_concrete = 3000 m/s
t = d/v >>> d = tv
The Attempt at a Solution
d = tv
d = (0.75 s)(343 m/s) = 257.25 m
t = d/v
t = (257.25 m)/(3000 m/s) = 8.575 s
d = (8.575 s)(3000 m/s) = 25725 m
So, the rock was 25725 meters away?
I feel like that is a huge distance, and that perhaps I should have stopped at 257.25 m and used that as my answer instead of plugging the value back into the equation. How do I find the time that passed before he heard the rock through the concrete?
If I use 257.25 m as the answer, it would be assuming that the time it took for him to hear it through the concrete was almost instantaneous.