Question

A diver is 7ft above water. The diver descends 12ft in total. How deep is he in the water?

Answer 1

Hint: It has been given to us in the question, the height from which the diver is going to make the fall or jump into the water. The value of this height is given as seven feet. Also, the total height that the diver descends from the position of his jump to the maximum depth under water is given to us as twelve feet. This is the total distance travelled by the diver in his free fall, first under the effect of gravity alone and then under water, where gravity as well as the Buoyant force of water that is upward in direction is acting on the diver.

Complete answer:
To find out how deep the diver is in water, we need to subtract the height at which he is standing above the water from his total descend after jumping. This can be written as:
Depth under water = (Total descend)-(Height above the water surface)
It is given in the problem:
Total descend = 12ft
Height above the water surface = 7ft
Therefore, the depth under water is equal to:
$\begin{align}
  & =12-7ft \\
 & =5ft \\
\end{align}$
Hence, the diver is 5 feet deep in water.
It should be known that the reason why the diver finally stopped descending further was the buoyant force of water acting on the diver, once he entered the water. The magnitude of this buoyant force increases as the depth increases, and thus the diver comes to a stop.

Note:
These problems will qualify as an easy problem but we would still need to be very careful while solving them. We should be well aware of the vocabulary terms used in these types of problems like the height of ascent or total descend, etc. or we may end up not being able to solve these problems.