Given:
Time of travelling is, 14 hours.
Travelled height is 140 feet.
The objective is to find the height of the submarine after 5 hours.
Since, it is given that the submarine is descending at a constant rate.
Then, the constant speed can be calculated as,
![\begin{gathered} \text{Speed}=(Dis\tan ce)/(Time) \\ s=(140)/(14) \\ s=10\text{ ft/hr} \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/s346yo5qg20171cp8130sqnbsql6gi2agl.png)
Now, the height after 5 hours can be calculated as,
![\begin{gathered} s=(Dis\tan ce)/(Time) \\ \text{d}=s* t \\ d=10*5 \\ d=50\text{ ft.} \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/6av7c40w7oae92dord7wu0fnu4twv96ivg.png)
Hence, the height of the submarine in downwards after 5 hours is 50 ft.