A submarine emits a sonar pulse, which returns from an underwater cliff in 1.02s. If the speed of sound in salt water is 1531 m/s. How far away is the cliff from the submarine?

Given,
Speed of the sound in seawater $\mathrm{v}=1531\mathrm{m}/\mathrm{s}$
Distance traveled by sonar pulse = 2 x depth of the sea = 2d
We know that, Distance = Speed x Time
$\Rightarrow 2\mathrm{d}=\mathrm{Speed} \mathrm{of} \mathrm{sound}\times \mathrm{time}$

 $\Rightarrow 2\mathrm{d}=1531\times 1.02$ 

$\Rightarrow 2\mathrm{d}=1561.62 \mathrm{m}$
$\Rightarrow \mathrm{d}=\frac{1561.62}{2}=780.81$
The submarine is located 780.81m from the cliff.