# Pressure in U-tube

## 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 ! ## 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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Doc Al
Mentor
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!

kuruman
Homework Helper
Gold Member
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 ^^

ideasrule
Homework Helper
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.