A boy stands near a vertical cliff and shouts. The echo of his shout reaches him after 2.6s. Assume the day is still and the speed of sound in air is 330m/s.
(i) Calculate the distance of the boy from the cliff.
(ii) The boy then walks 165m straight towards the cliff and shouts again. How much time now elapses before he hears the echo?
(iii) By how many seconds did the time interval between the shout and the echo change because of his movement?