Question

The smoke from the gun barrel is seen 2 second before the explosion is heard. If the speed of sound in air is 340ms^-1, calculate the distance of the observer from the gun. State the approximation used. 

Answer 1

The light has a much larger speed (= 3 × 10⁸ms^-1) in comparison to the sound (= 340ms^-1), therefore we can assume that the light takes negligible time and the sound takes 2 second to reach the observer.

Now speed = (Distance travelled)/(Time taken)

∴ Distance = Speed x Time

= 340 x 2 = 680m.