While giving a couple of numerical examples, the tutor reminisces about sound.

When I was a kid I played baseball.  In that town, there wasn’t much else to do except play it or watch it.  The men played softball.

I recall lying in the summer heat, watching from the grass far beyond the left field fence. The pitcher threw underhand, the ball arced through the air, and the batter swung.  The ball started up and away.  Then, I heard the metallic “conk” of the aluminum bat striking the ball.  I remember being surprised how late the sound reached me after I’d seen the ball take off.

Looking back, I might have been about 180m from home plate.  The temperature was likely around 28C.  The speed of sound, s, in metres per second, is given by

s=(332 + 0.6T),   where T is in degrees C.

The speed of sound that day would likely have been 332 + 0.6(28) = 348.8 ≈ 349m/s.

Given my distance of 180m, and the fact that

time=distance/speed

it would have taken about 180/349 = 0.516 ≈ 0.52s, or about half a second, for the sound to reach me.

One more recollection: Maybe the same year as the event above, I saw a documentary about the first nuclear test in the American southwest. One of the scientists had watched the explosion from an observation post that, I believe, was 10 miles away. He commented that the light flash from the explosion was instantaneous. “Then, a long time later…the sound.”

Let’s imagine the temp in that situation was also 28C, in which case the speed of sound, as calculated above, would have been 349m/s. If I recall, there is roughly 1600m to a mile. The scientist’s observation post was 10(1600m) = 16000m from the blast site. How long did the sound take to reach him?

time=distance/speed=16000/349 = 45.8s ≈ 49s

The scientist might have waited about 49 seconds between the light flash and the sound from the atomic test.

Well, that’s all for today. I hope you enjoyed the memories:)

Source:

Heath, Robert et al. Fundamentals of Physics. Heath Canada, 1981.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.