P= F/A vs. P only dependent on depth

[SaintJude]

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So, the answer is D because "pressure depends on only depth and density" However, then how does the equation P = F/A play into this?

Why is it wrong to try to determine the bottom of the pressure by using P= F/A?

 

[milski]

It's not wrong. But you need a reasonable way of determining what the force is without using the pressure. You should get the same result.

Edit: and that's exactly what aSagacious did in the next post.

 

[aSagacious]

Pressure = force/area (where force = weight of the fluid)

Force = mass*gravity, so plugging this into the above...

Pressure = (mass*gravity)/area

Mass = density*volume, so plugging this into the above...

Pressure = (density*volume*gravity)/area

I'm now going to write this equation suggestively:

Pressure = (density*gravity) * volume/area

Volume/area = length (or in this case height), so your equation reduces to:

Pressure = density*gravity*height

 

[MedPR]

It's not wrong. aSagacious showed how the rule that pressure at the same depth is equal regardless of the container was derived.

 

[ljc]

Something which might help clarify:
Inside the containers, pressure at height H is equal. However, if you were to place all three of those containers on top of a block, container C would apply the greatest pressure at that point, due to having the smallest contact area over which the force is applied (if we assume all 3 weigh the same, and that C has the smallest lower surface - although B might actually. Whatever)