Question:
A rule for finding your distance from a lightning flash is to count seconds
from the time you see the flash until you hear the thunder and then divide the
count by 5.
The result is supposed to give you the distance in miles.
Explain this rule and determine the 
error in it at 
and 
pressure.
Devise a similar rule for obtaining the distance in kilometers.
Solution:
Since the speed of light is 
, we will take
for this calculation.
At a temperature of 
, and pressure of the speed of sound is 
.
Therefore, for a person standing a distance d from the lightning,
the time between the light and the sound arriving is
.
Therefore, by counting a time 
between the light and sound corresponds to a
distance traveled of
.
This rule is good to 
.
Converting to miles (
), gives
.
This is good to 
.