Consider the above drawn tanks (Tank 1 left Tank 2 Right)
What Would the hydrostatic pressure from the water at the points where the arrows are drawn.
In Case 1 for example
Tank 1) Hydrostatic pressure from atmosphere + hydrostatic pressure from the part sticking out
Is this the same for Tank 2) where as Tank 2 is closed from the top.
is the hydrostatic pressure in this case equal only that from the part that is sticking out but not from the atmosphere? (because it's closed)
Now consider this cube with the sides of each $1$ meter and the height of tube of $4$ meters.
Suppose we need to calculate the force on A1 (top part of the cube)
Do we say $F=A\cdot p$? Where as $A=1\ \mathrm m\times1\ \mathrm m-\pi r^2$ removing the area of the tube
and then putting in $p=p_0+\rho\cdot g\cdot4\ \mathrm m$, where as $p_0$ is pressure from the atmosphere.
What if we calculate force on F2. Is it just full area multiplied with the pressure that is from the atmosphere and the pressure at depth of $5$ meters?
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$\begingroup$ Related question: Does Pascal's Law hold true in this scenario? $\endgroup$– BioPhysicistCommented May 2, 2020 at 15:24
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$\begingroup$ Related question: Can covering an open container with a lid change the pressure of gas in the container? $\endgroup$– BioPhysicistCommented May 2, 2020 at 15:24
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$\begingroup$ Related question: Varying pressure in container with aperture $\endgroup$– BioPhysicistCommented May 2, 2020 at 15:25
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1 Answer
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In the tank question pressure In both the cases will be same while in first case it is p°+hdg In other case the pressure will be due tupper surface I.e Roof of the container which is equivalent to 1st As the system is in equilibrium(assuming) Patm(A1) +mg = p (liquid)A1
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$\begingroup$ For layer between the top surface and just below it you nee to know the mass $\endgroup$– user261394Commented May 2, 2020 at 5:57
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$\begingroup$ So it does not matter if its closed or not, we still add the pressure from the atmosphere. $\endgroup$– MadCommented May 2, 2020 at 5:57
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$\begingroup$ It does if the outward stick had been closed it would have been different but we need conditions for that $\endgroup$– user261394Commented May 2, 2020 at 5:58
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$\begingroup$ but in the right picture it is closed. Did you see the picture? $\endgroup$– MadCommented May 2, 2020 at 6:02
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$\begingroup$ I thought that was water layer only $\endgroup$– user261394Commented May 2, 2020 at 6:03