Is Archimedes principle always obeyed or under what conditions is it not?

[studiot]

I am starting this as a diversion from the increasingly silly thread about flight, but the discussion is meant to be applicable to both liquids and gases.

 

The heading states the question.

 

Answers have implications for the correction to weighing in air, ships stuck on sandbanks, slip gauges, offshore vertical pipes, dams ... the list is long and varied.

[Greg H.]

I'm not familiar with the maths behind it, but I know you can affect the boyancy of water by changing the composition of it. For example, water with very high salt concentrations (such as the Dead Sea) is much more boyant that normal sea water (so much so that people routinely float unaided on its surface).

 

However, since we have changed the chemical makeup of the solution, I'm not sure what that does to the density. It's entirely possible that Archimedes holds true, even though we're displacing a smaller volume of water, because the density of the water is higher.

Edited December 5, 2014 by Greg H.

[studiot]

Yes Archimedes still holds true for bodies wholly or partially immersed in salt water, unless they are grounded on a sandbank.

[Delta1212]

I'm not familiar with the maths behind it, but I know you can affect the boyancy of water by changing the composition of it. For example, water with very high salt concentrations (such as the Dead Sea) is much more boyant that normal sea water (so much so that people routinely float unaided on its surface).

 

However, since we have changed the chemical makeup of the solution, I'm not sure what that does to the density. It's entirely possible that Archimedes holds true, even though we're displacing a smaller volume of water, because the density of the water is higher.

Things in salt water are more buoyant. Salt water itself is less buoyant. Both are the result of salt water being denser than fresh water, which yes, allows objects to displace a smaller volume to reach the same weight.

[studiot]

This does indeed address situations when Archimedes principle is obeyed, but not the question I asked which was, to paraphrase,

 

What happens if and when it is not?

[michel123456]

In outer space.