1- An explosion takes place on a boat. A ship's sonar detector picks up the signal 2.2s before the sound is perceived by sailors on the deck of that ship. How far away from the ship is the ship? The modulus of the speed of sound in water is 1500 m/s.

2-The modulus of longitudinal wave velocity in a lead pipe is equal to 1327 m/s. We consider a series of connected lead pipes with a total length of 104 m. If we hit a hammer blow at one end, why do we hear two blows at the other end? Calculate the time interval between the reception of each of the two sound signals.