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Sphere floatation in h2o  
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Posted by: proace ^{®} 08/12/2004, 22:32:29 Author Profile Mail author Edit 
This question I really don't need to know but it would be nice if someone could answer it. For expample: There are two individual hollow sphere's. Both are made of the exact material and are of the same weight and volume and both are sealed except, one is internally at normal sea level pressure and the other is at a high vacuum, lets say 50,000' The question: If both were submersed in H20 at a measurable depth approx 1000' and then released at exactly the same instant, would one travel faster and resurface before the other? Thanks for the answer.

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Re: Sphere floatation in h2o  
Re: Sphere floatation in h2o  proace  Post Reply  Top of thread  Forum 
Posted by: brewnog ^{®} 08/13/2004, 11:44:28 Author Profile Mail author Edit 
No. If they are both the same weight and volume, they will exhibit identical floatational characteristics. Obviously for this to be the case, they will not be identical designs because air does have density, and for your conditions to apply, the lost weight in the vacuumed sphere would have to be compensated for by ballast of some sort. 
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Re: Sphere floatation in h2o  
Re: Re: Sphere floatation in h2o  brewnog  Post Reply  Top of thread  Forum 
Posted by: zekeman ^{®} 08/30/2004, 11:00:42 Author Profile Mail author Edit 
I would agree if the volume of the sphere did not change. The net force upward would be the buoyant force minus the weight of the sphere and by Archimedes principle the buoyant force is equal to the weight of the displaced water, Therefore the sphere would accelerate upward according to Newton's law F=ma where F is the the net force, m is the mass of the sphere and a is the acceleration.As you can see the two variables F and m control the acceleration. Without further information, since we do not know the volume in each case, a definitive answer is not possible. 
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