When is an object positively buoyant?
When it displaces a volume of water weighing more than its own weight.
When is an object negatively
... [Show More] buoyant?
When it displaces a volume of water weighing less than its own weight.
When is an object neutrally buoyant?
When it displaces a volume of water weighing the same as its own weight.
Why two pieces of equipment do you use to control your buoyancy?
BCD, Lead weight
What does buoyancy help with when you are underwater?
Controlling where you are
What does buoyancy help with when you are at the surface?
Floatation, conserving energy
How does the buoyancy of an object differ in fresh/salt water?
More buoyant in salt than fresh
When you exhale what happens?
Lung volume decreases so you have less buoyancy.
When you inhale what happens?
Lung volume increases so you have more buoyancy.
Why don't you feel air pressure?
Your body is primarily liquid, which is incompressible and distribute pressure equally throughout your whole body.
Where are some air spaces located in the body?
Ears, sinuses, lungs
Do you always feel the pressure in body air spaces?
Only if the pressure is different inside and outside the air spaces.
1 bar is what depth?
0m/0ft
2 bar is what depth?
33ft/10m
3 bar is what depth?
66ft/20m
4 bar is what depth?
99ft/30m
How is air volume affected when depth is increased?
It decreases
How is air density affected when depth is increased?
It increases
What happens if you take an air volume underwater with you in a flexible container or inverted jar?
As pressure increases the volume decreases, same air but smaller space.
How do you maintain air volume as you descend?
Equalize
What is a "squeeze"?
As volume decreases, pressure pushes body tissues inwards toward air space, causing discomfort. Pressure outside air space is more than pressure inside air space.
Where can you get a squeeze?
Ears, sinuses, mask, lungs, teeth
How do you equalise air spaces in ears?
Blow and squeeze nose, wiggle jaw, swallowing
How often should you equalise?
Every metre before discomfort
What do you do if you feel discomfort?
Ascend until discomfort eases, equalise, continue descent slowly
Why can't you scuba while sick?
Congestion can plug air passages so you can't equalize [Show Less]