An explosion happened 1.75 km away from a point A and the sound from the explosion took 5 seconds to reach the point A. Calculate the speed of sound.
The sound of an explosion on the surface of a lake is heard by a boatman 100 m away and by a diver 100 m below the point of explosion.
(i) Who would hear the sound first: boatman or diver?
(ii) Give a reason for your answer in part (i).
(iii) If sound takes time t to reach the boatman, how much time approximately does it take to reach the diver?