# Could use help before Sunday the 15th

I've convinced a local pool to let me do a pressure check on an invention that I'm working on, Sunday the 15th, but I've only got about 15 or twenty minutes to get it tested.
What I need to do is to weight down approximately a gallon container of air down to a depth of 12 feet, and to do this I've got two 15 pound weights from a barbell.
The question is, can I get this container down that far by just useing one of the weights?

Related Classical Physics News on Phys.org
How's this an invention? What purpose does this serve?

I'm working on a new alternative energy principle, it's part of the system, although, not to spec, but it will give me I hope three answers.

I think that the force of buoyancy = (mass of fluid displaced) - (mass of object).

In this case, air has a density of 1.2kg/m^3. 1 gallon = .00379 cubic meters. 1.2kg/m^3*.00379m^3 = .00454 kg, which equals .0100lbs. So, 1 gallon of air equals .0100 pounds.

one gallon = .00379 cubic meters

well you are essentially pushing up one gallon of water. this weighs:

one gallon of water has a weight of .998g/cm^3 =998kg/m^3:: 998kg/m^3*.00379m^3 = 3.78kg::<b>8.33lbs.</b>

your weights weigh 15 pounds, but also have boyancy.

water has a density of 8.33 lbs/gallon.Assuming your weights have a volume of less than 2/3 of a gallon, you should be fine (2/3 of a gallon weighs about 5.6 lbs. your weight weighs about 9.4 lbs more, so that should overcome the 8.33lbs of buoyancy of the gallon of water). if they have a volume of 1 gallon, you will need both weights.

i hope that makes sense...

russ_watters
Mentor
You're working on an alternate energy invention involving buoyancy and you don't know how to calculate buoyancy? :surprised

my knowledge at this time is the principle of the working parts of the application in that it's what I have worked on, and I have gone through its machinations, this part of the test is only by degree.
But since I only have a little time to test it, I don't want to secure another weight that will not ad to the understanding of what I'm looking for, but just ad more weight I would need to lift when the test is over.
Once I do my test, hopefully I will be correct in my ingenuity.
PS, by the way the container of air will have other pieces connected, I didn't mention this, because I was only looking for the one answer so far.

Last edited:
Had my test, and didn't concieve one problem, I don't weigh much, and since I didn't take a weight belt to keep me down underwater, it was a nightmare just trying to stay underwater at a depth of five foot.
But I did test it at this depth briefly, it made me realize that I need to make my prototype device larger, and as far as my allotted fifteen minutes, it has now been extended to any Sunday, they evidently liked the premise?

Last edited: