A research ship uses ultrasound pulses to measure the depth of an ocean trench.
The speed of ultrasound in sea water is 1500 m/s.
The ocean trench floor is 6000 m below the ship.
An ultrasound pulse is emitted from the ship.
How long is it before the ultrasound pulse returns to the ship?
Use the equation: distance travelled=speed×time\text{distance travelled} = \text{speed} \times \text{time}distance travelled=speed×time
2.0 s2.0\text{ s}2.0 s
4.0 s4.0\text{ s}4.0 s
8.0 s8.0\text{ s}8.0 s
16.0 s16.0\text{ s}16.0 s