Question

A boy fires a gun and another boy at a distance hears the sound of fire 2.5s after seeing the flash. If the speed of sound in air is 340m/s, find the distance between the boys:
A. 850 m
B. 8500 m
C. 1700 m
D. none of these

Answer 1

Sound waves are longitudinal waves that must pass through a medium, such as air. Also, sound travels quite fast; it is still possible to measure its speed in air. When we need to measure the time it takes a sound to travel a measured distance.

Complete step by step answer:
According to question given that,
Time is taken by another boy to hear the sound of fire $= 2.5s$
Also, the speed of sound is given as $= \;340m/s$
To find the distance, we apply the formula:
Distance (d) = speed (S) × time (t)
Therefore distance (D) = $340m/s \times \;2.5s\; = \;850m$
Thus the distance between the two boys is 850m.

Hence the correct option is (A).

**Additional information :**speed, distance and time all are scalar quantities because they show only magnitude, not direction. It can't be zero and negative; they are always positive. It is only one-dimensional motion. Speed of light in a vacuum is $3 \times {10^8}\;m/s$ .

Note: Remember when the propagation of the sound waves requires a medium, without any medium, it is not possible to propagate sound waves or to hear the things. Sound is a form of energy and produces sensation in our ears to hear the things. The vibration of molecules produces it. Another two forms of waves in which sound travelled are:
(i) Longitudinal waves
(ii) Transverse waves