Question

An object is $11km$ below sea level. A research vessel sends down a sonar signal to confirm this depth. After how long can it expect to get the echo? (Take the speed of sound in seawater as $1,520m/s$)

• A. 15.30 s
• B. 14.47 s
• C. 12.20 s
• D. 11.13 s

Answer 1

The correct option is B

14.47 s

The total distance travelled by the sonar signal from the ship to the sea bed and back:
$S$ = $2\times 11km$ = $22,000m$
Time taken by the sound to travel this distance is:
$t=\frac{s}{v}=\frac{22000m}{1520m/s}=14.47s$
$\therefore$ The echo will reach the ship $14.47$ seconds after the signal is sent.