Water as weight rather than lead?

[Afraid_of_Fish]

OK here is all the info I have....

1. The witches are red heads (we all know red heads are evil.. or at least misunderstood).
2. Ducks are very suceptable to narcosis so all ducks breath heliox for safety when diving.
3. It is summer time, however the dive takes place in a lake at MACHU PICHU in the southern hemisphere where it is now winter.
4. MACHU PICHU is 9060' above sea level
5. The water temp is 71f
6. The duck is diving comando, the first witch is in a mares semi-dry and the second witch is in a henderson 7/5mm hyperstretch suit.
7. Mercury is in retrograde
8. vis is about 20 feet
9. Witches don't like Salem Mass.
10. water freezes at 32f
11. A ducks quack doesn't echo, the mythbusters guys were wrong.
12. The earth rotates counterclockwise.
13. is an unlucky number
14. The volume of the caspian sea is 88 million cubic meters.
15. The chicken came before the egg
16. There are no left handed birds

If you need additional info, please use an almanac or search on line.

Thanks,

TT

By the way the answer is:

1 jug of indeterminate size each.

Not if it's Sunday. On Sunday's all witches go to Salem Mass. for all their diving, and we all know the vis. in mass. isn't anywhere near 20 feet. it is also much colder, therefore the ice (Which is floating on the top as mo2vation pointed out often happens on page one) requires the duck to need an extra layer for warmth. The witch which is carrying the duck (ducks can't swim) needs more weight. Unless, of course, it is made of wood, in which case you would be correct. Der, haven't you ever seen the movie?

 

[Curt Bowen]

I was one of the buddies that was with H2 and it was a real question that I think on the surface is worth asking, if for nothing else but to see all the interesting answers to it. I'm glad he asked it.

Well at least someone was daydreaming during the surface interval. You could weight yourself down with water. About 70 gallons of salt water, diving in fresh water might work, but it would be hard to swim dragging all those jugs along.

 

[beachbum70635]

You wouldn't get very far with that. The amount of positive buoyancy you create depends on the mass of the water displaced and both the volume and the mass of the object displacing the water.

This much should be clear.

If you use water to fill a BCD then you're displacing a certain volume of water (indeed increasing the volume of the diver) but you've taken on a mass of water equal to the volume you have displaced (increasing diver mass). Since you've done both, increasing both volume and mass with the same liquid you're immersed in, then your buoyancy won't change.

I hope that sounded logical.

The reason air works to create positive buoyancy is taht you displace a volume of water with something much lighter than water. My original comment assumed you were increasing the volume of the flexible container with air.

R..

Totally logical to me. That was the point of my question. Diver0001's statement was lacking some info. There are many ways to increase the volume of that flexible object, but not all of them will make it more buoyant.

 

[glbirch]

Water at 4C is 1.0g/cm3. Water at 70F (about 21C) is 0.998g/cm3.

IF your body doesn't change density, then you would gain buoyancy in the colder water. Only about 2 parts per 1000, or about 1/2 pound for diver + gear of 250 pounds total.

OTOH, if various bits of your body shrink in cold water, you might be denser too. :banana:

Come to think of it, somebody who purposefully dives in 4C water has got to be really dense.

Hey, nothing wrong with diving in 4C water. If nothing else it teaches you tolerance, and an appreciation for all the tropical diving.

Yes, the diver would gain bouyancy within his bubble of cooler water. However, don't forget that the bubble of cold water has now just lost bouyancy with respect to the ocean around it and will start sinking, creating a diver-sized downcurrent.

 

[glbirch]

And, while I'm on a roll...the original poster stated that a gallon of water weighs about 6 pounds. It is actually more like 8.5 pounds per gallon. The old saying still holds true: a pint's a pound the world around.

Mr. Know-it-all (or so I think)

Should have stopped while you were on a roll. Pint's a pound, but no one ever agreed on gallons. US gallons are around 8.5 pounds water, while a British Imperial gallon is 10 pounds.

(I know; picky, picky... )

 

[FreeFloat]

Interestingly enough...........

Say you wanted to lift an object off the lake bed - how about a lost boat anchor. You've seen similar anchors ashore so have a rough idea of the size. You're trying to select how many and what size of lift bags you'll need for the project.

I had an instructor tell me that if you can visualize the same object, on land, made of ice you'll have a pretty fair guess as to its actual "weight" underwater! Remembering of course that an item will "weigh" less in water due to its displacement. Therefore a 250# anchor may only require 200# or so of lift bags to lift it.

Food for thought.........

 

[jhelmuth]

I can hardy contain myself...

So I guess that Archemedies (sp?) principle was not well understood in class. If you look this up you'll get your answer.

Diving is mostly physics and Physiology. Throw in some excellent skills and a decent computer (your brain that is!), and you are there!

 

[Mako Mark]

The old saying still holds true: a pint's a pound the world around.

Actually, a pint is a pound only in some funny country that lies between Canada and Mexico, the rest of the world it is about 600 milliliters, therefore about 600 grams of water. The exception being where a pint is a frosty all natural beverage made from partially germinated grain and flowers.

 

[TCDiver1]

Actually, a pint is a pound only in some funny country that lies between Canada and Mexico, the rest of the world it is about 600 milliliters, .....

Its okay Mark, we don't mind that the rest of the world has it wrong.

 

[widebody50]

Should have stopped while you were on a roll. Pint's a pound, but no one ever agreed on gallons. US gallons are around 8.5 pounds water, while a British Imperial gallon is 10 pounds.

(I know; picky, picky... )

Thanks for the correction...so, I guess hoisting a pint in jolly old England is a better prospect than I originally thought! lol :11ztongue