FishOutUvH2O
Contributor
Physics should be a requirement in school, not an option!!!!
Am I really weightless ?
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Truth of the matter is you're not weightless underwater. Gravity is still pulling on your guts. In order to be weightless (under the influence of microgravity, in NASA-speak), you have to be in a situation (orbit) where the centrifugal force on you equals the centrepital force on you. Only then will you be truly weightless. You can make yourself weightless in an airplane for a short while by doing a parabolic curve (FUN!!) but it doesn't last long.
However, whan you're underwater it feels like you're weightless. I would think it's the closest thing to being in space without really being there.
However, whan you're underwater it feels like you're weightless. I would think it's the closest thing to being in space without really being there.
Blackwood
Contributor
Newbie100
Registered
First Start with 10% of your body weight, then more weight is for your wet suit thickness and fresh vs salt water, and more weight for a dry suit. There is no exact formula that I am aware of. Go back to your open water text and they tell you about how much to add for these items (no formula). Then you have go in open water and be able to float at eye level with your BCD empty, you may have to experiment and add or drop a few pounds. A few pounds should be added for an aluminum tank which becomes buoyant when lower on air further on in the dive (or you can perform this test with a nearly empty tank in a pool and know exactly how much to add for the tank. Whenever you make any equipment changes BCD wet suit/ Drysuit etc the you repeat this procedure.
Welcome to ScubaBoard. This has been a confusing thread, and I am not sure your response is in keeping with its intent, although I am not sure what that intent may really be. I would like to respond to some of your points, though.
Even though each of us is different, this oft-repeated advice leads most people to start with far too much weight. If I followed that advice for, say, a 3 mm suit, I would be wearing more than 3 times as much lead as I need. With all the different situations in which I dive, I rarely need as much as 10% of my body weight. Only if I am diving a conventional BCD and a dry suit, heavy underwear, and single aluminum tank, will I need about 10% of my weight.
I think most people wear much too much lead and are convinced that they need it.
This is correct.
This is more oft-quoted advice that is not totally accurate. It does not matter whether the tank is aluminum or steel. If you lose 5 pounds of air during a dive, you are 5 pounds more buoyant at the end of the dive. An aluminum tank will float when it is empty and most steel will not, but steel tanks are still 5 pounds lighter if they lose 5 pounds of air during the dive.
Even though each of us is different, this oft-repeated advice leads most people to start with far too much weight. If I followed that advice for, say, a 3 mm suit, I would be wearing more than 3 times as much lead as I need. With all the different situations in which I dive, I rarely need as much as 10% of my body weight. Only if I am diving a conventional BCD and a dry suit, heavy underwear, and single aluminum tank, will I need about 10% of my weight.
I think most people wear much too much lead and are convinced that they need it.
This is correct.
This is more oft-quoted advice that is not totally accurate. It does not matter whether the tank is aluminum or steel. If you lose 5 pounds of air during a dive, you are 5 pounds more buoyant at the end of the dive. An aluminum tank will float when it is empty and most steel will not, but steel tanks are still 5 pounds lighter if they lose 5 pounds of air during the dive.
markyd
Registered
Blackwood: actually, when you jump out of a plane, you DO feel the pressure of the air you are pressing against as you fall, so is that weightless or not?
tfsails: I've been out of school for a while, so I could be wrong, but I believe the "centrifugal force" is usually considered to be a reactive force to the centripital force, by definition, so your comment is a bit meaningless.
AGAIN, gravity still acts in space! It is an attractive force between anything with mass.
marky-d
tfsails: I've been out of school for a while, so I could be wrong, but I believe the "centrifugal force" is usually considered to be a reactive force to the centripital force, by definition, so your comment is a bit meaningless.
AGAIN, gravity still acts in space! It is an attractive force between anything with mass.
marky-d
Blackwood
Contributor
There is no such thing as centrifugal force.
If you are in water and your depth remains constant you are without weight. If you sink you have some and if you ascend you are negative weight. During the whole thing in water, in space, and even on the moon, your mass is constant.
If you are in water and your depth remains constant you are without weight. If you sink you have some and if you ascend you are negative weight. During the whole thing in water, in space, and even on the moon, your mass is constant.
I can't believe I'm still following this thread.
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