If you are going through the PADI Open Water Diver e-Learning and are keen to know more about the answers to the knowledge review questions, in this post I will cover Section 1 questions in full details.
In Section 1 of PADI’s Open Water Diver E-Learning, you will cover a first set of important diving concepts. They include buoyancy, water pressure and air volume effects, breathing underwater, equipment and some diving skills.
Going through the online theory is extremely important. Although not compulsory, doing so before you start your water sessions will help you become a good diver more quickly.
This is why is it also very important to go through the Knowledge review questions, particularly the ones where you have more difficulty.
If you understand all concepts in the knowledge review sessions, passing the final exam will be way easier.
If you are looking for explanations to other PADI Open Water knowledge review sections, check out the following links:
- PADI OWD Section 2 Knowledge Review Answers Explained
- PADI OWD Section 3 Knowledge Review Answers Explained
- PADI OWD Section 4 Knowledge Review Answers Explained
- PADI OWD Section 5 Knowledge Review Answers Explained
- PADI Open Water RDP Knowledge Review
- How to Use PADI Dive Tables
Let’s now take a closer look at the knowledge review questions from PADI’s Open water diver Session 1.
1. Something underwater that does not float and does not sink is?
When something underwater does not float nor sink, it is neutrally buoyant.
In water, any object can either float, sink, or neither float nor sink.
Using diving terms, an object can either be positively buoyant, negatively buoyant, or neutrally buoyant.
To better remember these concepts, think of an empty glass bottle. If you put it in the water upright, it will most likely float. If instead you remove all the air and submerge it, it will sink.
If you only partially remove the air from the bottle, it will neither float nor sink. It will be neutrally buoyant.
Buoyancy is extremely important in diving. Having a proper buoyancy will help you consume less gas, avoid touching the bottom and hurting marine life or yourself.
Most importantly, having proper buoyancy will allow you to stay at the depth you decide while diving and avoid sinking.
As you will learn during your open water diver course, a diver should always be properly weighted in order to achieve neutral or slightly negative buoyancy.
2. If an object is neutrally buoyant in salt water, what will happen to it if I put it in fresh water?
If an object is neutrally buoyant in salt water, if you put it in fresh water it will sink.
As you have learnt in Section 1 of your open water diver theory, different types of water have different density.
In particular, salt water is more dense than fresh water. Without entering complex physics concepts, I try to remember this by thinking that salt water is denser exactly because it contains salt.
If water is denser, an object will need to have a greater mass in order to sink.
Therefore, an object that is neutrally buoyant in salt water will be negatively buoyant in fresh water.
3. A diver is 30 meters/99feet underwater. The water pressure at this depth would be X times more than the pressure at the surface.
Water pressure at 30 meters or 99 feet underwater is four times more than water pressure at the surface.
To answer these types of questions you should always remember a very important concept in scuba diving.
As depth increases, the pressure of water surrounding your body also increases as compared to the pressure at the surface.
To remember by how much water pressure increases for a given depth, I use the following rule of thumb.
For every 33 feet (approximately 10 meters) of depth, the pressure increases by 1 atmosphere (1 ata). Pressure at the surface is one atmosphere (1 ata).
4. If I hold a glass full of air upside down, and if I take it to the bottom of the swimming pool without tipping it, the density (thickness) of the air inside the glass will be X at the surface.
If you hold a glass full of air upside down and take it to the bottom of a swimming pool without tipping it, the density of the air inside the glass will be greater than at the surface.
We just saw in the previous question that as we go down underwater, pressure increases.
If we bring along a sealed plastic bottle, we will see that its volume will reduce as we go deeper.
Although the volume reduces, the quantity of air it contains remains the same. It is however more compressed or more dense.
If you apply the same reasoning to a glass full of air, the glass will not compress as it is open. The air inside will however be more dense and occupy less space.
5. What should I do if I can’t equalize (clear) my ears or sinuses while I am descending (going down)?
If you are experiencing issues in equalizing your ears or sinuses while descending, you should stop and ascend a meter/few feet and try to equalize again.
At the beginning of a dive, it is quite common to experience some issues in equalizing your ears and sinuses.
Continuing the descent would only put you in a dangerous situation as you would risk an eardrum rupture.
Instead, you should slowly ascend until the pressure in your ears and sinuses reduces and try to equalize again.
Remember that trying to equalize your ears more strongly is also dangerous.
Instead of equalizing strongly, try to equalize for longer.
6. What should I do to prevent mask squeeze (a sucking or pulling feeling on my face and eyes)?
To prevent a mask squeeze, you should gently breathe into your mask through your nose.
This works exactly as your ears. In the open water theory, you have learnt that as you descend, you will need to equalize dead air spaces.
In fact, while descending, the air in your mask gets compressed just like the air in your middle ear.
While compressing, you will feel increasing pressure of your scuba mask skirt on your face.
To counterbalance such pressure, you will need to gently blow into your mask from your nose as you descend (and feel some slight pressure).
This will ensure that the dead air space between your mask and your face is always equalized. Although you can choose different types of scuba masks, you will need to equalize even the ones with the lowest air space.
7. I put air into a balloon underwater at 10 meters/33 feet and then I take it to the surface. The balloon will?
If you put air into a balloon underwater at 10 meters deep and bring it to the surface, the balloon will expand to twice the size.
In your open water theory, you have learnt that water pressure increases with depth.
As water pressure increases, air gets more compressed, and its volume reduces.
Water pressure increases at a ratio of 1ata every 33 feet or 10 meters, knowing that at surface the pressure is 1 ata.
This means that as we bring a sealed flexible object filled with air on a dive, its volume will reduce by ½ every 33 feet or 10 meters.
Therefore, if we put air into a balloon at 33 feet or 10 meters depth an bring it to the surface, its volume will double.
8. What can happen to me if I hold my breath while ascending on a scuba dive?
If you hold your breath while ascending on a scuba dive, your lungs will overexpand, which could cause serious injury.
To understand the answer to this question, think of the sealed balloon of the previous question.
We saw that if we inflate it at 33 feet / 10 meters depth, the balloon will double its size upon reaching the surface.
But what would happen if we inflate the balloon at its maximum capacity at 33 feet / 10 meters depth?
Upon surfacing, the balloon would increase in size and given that it is already at its maximum capacity, it will explode.
No need of illustration here but think of your lungs as a sealed balloon. If you hold your breath while ascending, they will overexpand.
If you are holding your breath and your lungs are at their maximum capacity, you will really risk some serious injury.
This is why, the most important rule in scuba diving is to never hold your breath.
9. What is the most important feature of a scuba regulator?
The most important feature of a scuba regulator is how easy it is to breathe from.
Scuba diving regulators come in different shapes and forms, and different models are better suited for different diving conditions.
Some regulators are better for cold water diving, whereas some others are more suited for warm water diving.
Some regulators have some valves and knobs that help you regulate the gas flow, some others don’t.
Irrespective of their shape, size and colour, all regulators have one essential quality in common.
They need to be able to provide a diver with gas at a relatively constant flow at any given depth.
In other words, the most important feature of a regulator is how easy it is to breathe from.
10. Diving is Easier, Safer and more fun when I:
Diving is easier, safer, and more fun when you dive with a buddy.
Imagine you decide to go on a dive by yourself and after 40 minutes your diving computer blacks out.
You decide to slowly start ascending but have no clue of the depth, time, and ascent rate.
You therefore are not even able to do a 3 minutes safety stop at 5 meters with certainty. If you are lucky, nothing will happen.
If you are unlucky you could suffer from decompression sickness because you did your safety stop way too close to the surface without realizing it.
Now, imagine the very situation, but this time you are not alone. You signal the computer failure to your buddy and ask him to abort the dive.
He will then signal you when is the moment to do the safety stop, and he can comfortably check the adequate ascent rate on his diving computer.
It’s not difficult to conclude that the second situation is way safer. This is why you should always dive with a buddy.
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