Physics!!!?
An important news announcement is trans- mitted by radio waves to people who are 65 km away, sitting next to their radios, and by sound waves to people sitting across the newsroom, 4.7 m from the newscaster. Take the speed of sound in air to be 344 m/s.
What is the difference in time that the mes- sage is received?
Answer in units of ms.
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Answers & Comments
radio waves speed is the speed of light, i.e. 300*10^3 km/sec...therefore :
t1 = 65/(300*10^3) = 0.22 msec
t2 = 4700/344 = 13.66 msec
t = t1+t2 = 13.66+0.22 = 13.88 msec
The time for radio waves to travel 65 km is (6.5 x 10^3m)/(3.0 x 10^8 m/s) = 21.7 microseconds.
The time for sound waves to travel 4.7 m is (4.7 m)/(344 m/s) = 13.7 ms.
The "difference" could be reported as 13.7 ms.
But it's not quite true, as the distance from the newscaster to his microphone is not zero, and the distance from the radios to the people who are sitting "next to" their radios is not zero, either.