1. A ship is sailing in dense fog and it could be close to dangerous cliffs. The captain switches on the fog horn. The horn sounds and the echo is heard 4 s later. The speed of sound in air is 340 m/s.
a. Calculate the distance between the ship and the cliff.

b. Next time the fog horn sounds it takes 3.5 s for the echo to be heard. State whether the ship is further from, nearer to or at the same distance from the cliff.