A sonar unit on a submarine sends out a pulse of sound into seawater. The pulse returns 1.28 s later. What is the distance to the object that reflects the pulse back to the submarine?
This process depends on the sort of water (saltwater, ...) and the temperature. The only value of the speed of sound in water which I have at hand is:
$\displaystyle v_s = 1485\ \frac ms$
The distance traveled by the sound signal is:
$\displaystyle d = 1.28\ s \cdot 1485\ \frac ms = 1900.8\ m$
Therefore the object is at a distance of 950.4 m