(a) A man standin

a. Let speed of sound = v

Difference of man from the class = d

Time taken to hear the who = 3.5s

Velocity of the sound wave to reach the person before he moved closer

Distance of the man = d – 84

Time taken = T= 3 s

b. The loudness or softness of a sound is determined basically by its amplitude. The amplitude of the sound wave depends upon the force with which an object is made to vibrate.

C. The total distance covered by the sound from the point of generation to the reflecting surface and back should be at least (344 m/s) × 0.1 s = 34.4 m. Thus, for hearing distinct echoes, the minimum distance of the obstacle from the source of sound must be half of this distance, that is, 17.2 m.