dive physics problem.. a challenge for you...

[KangarooSeatbelt]

Ok guys.. I'm taking a class and the instructor has given us a dive physics problem... see if you can solve it! I'd like to see how you got there, as well as the actual answer.... we had a lot of fun with it, so I thought I'd see what everyone here could do.

You find a 5000 pound anchor with a volume of 10ft3 (10 cubic feet) in 68 ft of sea water. You want to get it to the surface so you can use it for your decoration on the front lawn of your house. Fortunately, you happen to have a 6000 lb lift bag. You also have an Aluminum 80, a Steel 104, and a steel 72. Do you have enough air to get it to the surface?
Approximately what volume of air is required to lift the anchor?

See what you can do... remember boyle's law and to take into consideration the weight of air..

-Sam

 

[jonnythan]

Nice try at getting us to do your homework for you.

 

[wedivebc]

Ok guys.. I'm taking a class and the instructor has given us a dive physics problem... see if you can solve it! I'd like to see how you got there, as well as the actual answer.... we had a lot of fun with it, so I thought I'd see what everyone here could do.

You find a 5000 pound anchor with a volume of 10ft3 (10 cubic feet) in 68 ft of sea water. You want to get it to the surface so you can use it for your decoration on the front lawn of your house. Fortunately, you happen to have a 6000 lb lift bag. You also have an Aluminum 80, a Steel 104, and a steel 72. Do you have enough air to get it to the surface?
Approximately what volume of air is required to lift the anchor?

See what you can do... remember boyle's law and to take into consideration the weight of air..

-Sam

Easy, you need 4360 lb lift to get it up. At 64lb per cubic foot you would need 68.125 cuft at the surface but since it as at 3.06 ata depth you will need 208.5 cuft.
You have 80+104+72 = 256 cuft - 208.5 cuft air to spare
OK Sam so applying the rule of thirds and assuming a sac rate of .6 cuft per minute how long could you stay at that depth on the remaining air?

 

[jonnythan]

Why would you apply the rule of thirds to this dive?

 

[DandyDon]

I'm just tinkering here: According to the Univ of Phoenix Online Conversion, 5000 Pounds of (fresh) water = 80.0936638 Cubic feet.

To lift the anchor, which is already displacing 10 cf, you'll need to displace 70.1 cf of water, which at 68 feet deep will require 210.3 cf of tank air, figured on freshwater. For saltwater, dividing by 1.026 spec gravity = 205 cf, as the anchor will be slightly more buoyant in saltwater.

Looks like you'd have enough, if the tanks were filled to capacity. You didn't specifiy that, but I'll presume that this is not a tank fill joke.

 

[rmediver2002]

Ok guys.. I'm taking a class and the instructor has given us a dive physics problem... see if you can solve it! I'd like to see how you got there, as well as the actual answer.... we had a lot of fun with it, so I thought I'd see what everyone here could do.

You find a 5000 pound anchor with a volume of 10ft3 (10 cubic feet) in 68 ft of sea water. You want to get it to the surface so you can use it for your decoration on the front lawn of your house. Fortunately, you happen to have a 6000 lb lift bag. You also have an Aluminum 80, a Steel 104, and a steel 72. Do you have enough air to get it to the surface?
Approximately what volume of air is required to lift the anchor?

See what you can do... remember boyle's law and to take into consideration the weight of air..

-Sam

weight of air would not have anything to do with the calculation, Boyle's law and Archimedes principle are used.

 

[jonnythan]

You guys couldn't resist could you.

 

[wedivebc]

Why would you apply the rule of thirds to this dive?

What dive? It was a hypothetical question

 

[jonnythan]

You're the one who asked the question applying the rule of thirds, but there's no reason to apply rule of thirds to this hypothetical dive.

 

[wedivebc]

You're the one who asked the question applying the rule of thirds, but there's no reason to apply rule of thirds to this hypothetical dive.

Not that it has any bearing on this thread but I apply the rule of thirds to every dive.
He asked a hypothetical question I answered and also asked a hypothetical question.