You can estimate your distance from a lightning storm by watching for a lightning flash and then counting in one-second intervals using the general rule that you are 1 km away for every 3 s you count.

Explain why this rule works.
Estimate the distance from a lightning storm if it takes 8 s (exactly) for the sound of the thunder to reach you after you see a flash of lightning. Assume that the temperature is 21 degrees Celsius. (The speed of light is approx. 2.99 x 10^8 m/s.)

3 answers

assume light travels at very very high speed so you see the lightning immediately.
Then distance = speed of sound * time
distance in km = (1/3) t
so
speed of sound must be about 1/3 km/sec
or about 333 m/s

8/3 km

12km