Solving Pressure in U-tube with Different Densities

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AI Thread Summary
In the discussion about the U-tube with two liquids of different densities, participants clarify that liquid A, with a density of 1.0 g cm-3, can indeed be on top of liquid B, which has a density of 0.8 g cm-3. The reasoning is based on the principle that pressure at a given point must be equal, requiring a greater height of the less dense liquid to balance the pressure exerted by the denser liquid. This challenges the common misconception that denser liquids must always be below less dense ones. The conversation emphasizes understanding fluid pressure dynamics rather than relying solely on density comparisons. Ultimately, the clarification helps participants grasp the concept of pressure equilibrium in U-tube scenarios.
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Homework Statement


Two liquids A and B of densities 1.0 g cm-3 and 0.8 g cm-3 are poured into an U-tube as shown in the figure below. Find x !

untitled.jpg


Homework Equations


P = \rho g h


The Attempt at a Solution


Is it possible liquid A is on top of liquid B because A has higher density than B?

Or do I misinterpret the question? Is it possible the question means density of A is 0.8 g cm-3 and B is 1.0 g cm-3 because there is no word "respectively" ?

Thanks
 
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songoku said:
Is it possible liquid A is on top of liquid B because A has higher density than B?
Sure, why not? Look at the diagram. Note that the height of liquid A is less than that of liquid B. There's a reason for that!
 
The statement looks correct, A is more dense than B. At the line PQ the pressure is the same. So more height of liquid above point P is needed to maintain the pressure the same as at point A.
 
Hi Doc Al and kuruman

Oh so it's possible that liquid with higher density is on top of liquid with lower density. I always think it's impossible.

I get it now. Thanks a lot Doc Al and kuruman ^^
 
songoku said:
Hi Doc Al and kuruman

Oh so it's possible that liquid with higher density is on top of liquid with lower density. I always think it's impossible.

I get it now. Thanks a lot Doc Al and kuruman ^^

Just imagine an iron piston pressing down on water in the U-tube and you'll see why it's possible.
 

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