lift and volume

[A. Berk]

Originally Posted by David

I already know how this is going to end but I ask anyway.

if a 3 liter bottle with open end has x lift at ten meters how much lift does it have at 70 meters. yes I know it will take more gas because of the presure but the volume 3 liters will remain the same. As the bottle rises to the surface the gas will expand and escape from open end but will it still have same lift at depth.

David :-)

If I'm reading this right, the question is; Will a given volume (3lt in this case) have the same lift at varying depths? Er, yes... a 3lt lifting device at 10m at 100% capacity has 6lt of air in it. Take it to 70m and give it 100% air capacity (24lt) and it has exactly the same lift capacity as it did at 10m.

Berko

[A. Berk]

Originally Posted by nigelH

Well at 10m it will have 6L (surface) of air in it (weight 7.8gms) and at 50m 24L (weight 31.2gms) so there is a loss in lift of 23.4 gms.

But that's less than 1%, about the same as three £1 coins.

Using that theory if you took the bottle deep enough (say 10,000 metres) the weight of the air inside would eventually make it negatively buoyant!

Berko

[BJ]

I would not normally have suggested this but some of you need to read my book : The Scuba Diving Handbook.
It explains things in very simple terms. It doesn't cost much either and you can get it from Amazon!

[Richard Mason]

Originally Posted by BJ

I would not normally have suggested this but some of you need to read my book : The Scuba Diving Handbook.
It explains things in very simple terms. It doesn't cost much either and you can get it from Amazon!

I was looking at that the other day in Book City, Hobart, the el cheapo outlet that stocks stuff no one else can sell at knock down prices.

[BJ]

Originally Posted by Richard Mason

I was looking at that the other day in Book City, Hobart, the el cheapo outlet that stocks stuff no one else can sell at knock down prices.

Sorry to disappoint you but the American publisher is still translating the Aussie version. We've had the battle over feet/inches and metric but they asked me what measurements you use (no joke). I said kangas and roos.

It's so cheap it will be used as toilet paper rather than remaindered!

[Richard Mason]

Originally Posted by BJ

Sorry to disappoint you but the American publisher is still translating the Aussie version. We've had the battle over feet/inches and metric but they asked me what measurements you use (no joke). I said kangas and roos.

It's so cheap it will be used as toilet paper rather than remaindered!

Yeah we get all that stuff dumped here.

[A. Berk]

Originally Posted by Richard Mason

I was looking at that the other day in Book City, Hobart, the el cheapo outlet that stocks stuff no one else can sell at knock down prices.

Still wasn't quite a bargain then Richard

kerBo

[A. Berk]

Originally Posted by BJ

It doesn't cost much either and you can get it from Amazon!

You can get Dengue fever from the Amazon for nowt... and I'd rather have that

koreB

[uwila]

Originally Posted by A. Berk

Using that theory if you took the bottle deep enough (say 10,000 metres) the weight of the air inside would eventually make it negatively buoyant!

Berko

Yes this is exactly right. As soon as the average density of the bottle reaches the average density of the water surrounding it, then the bottle becomes neutrally bouyant. Any deeper and it will become negative.

The lift of an open container (assuming the opening is pointing downwards!!!) is calculated by taking the weight of the water displaced and subtracting the weight of the container and the of gas within it. The deeper one goes, then the more gas needed to fill the container and therefore the lifting capacity goes down.

Because water is almost incompressible, its density does not increase very much at all at depth, whereas that of air does.


So the answer is exactly what Nigel said.

Cheers, Chris

[A. Berk]

Originally Posted by uwila

Yes this is exactly right. As soon as the average density of the bottle reaches the average density of the water surrounding it, then the bottle becomes neutrally bouyant. Any deeper and it will become negative.

The lift of an open container (assuming the opening is pointing downwards!!!) is calculated by taking the weight of the water displaced and subtracting the weight of the container and the of gas within it. The deeper one goes, then the more gas needed to fill the container and therefore the lifting capacity goes down.

Because water is almost incompressible, its density does not increase very much at all at depth, whereas that of air does.


So the answer is exactly what Nigel said.

Cheers, Chris

Why doesn't all that 'heavy' air drop out the bottom of the bottle?

kroeB