# pressure liquid

by batballbat
Tags: liquid, pressure
 P: 127 what would the pressure of liquid at a depth be in a container which is slanted?
 P: 127 i suspect $$h.d.g.sinAngle$$. correct me if i am wrong
 Mentor P: 21,652 No, the shape of the container is irrelevant. http://en.m.wikipedia.org/wiki/Fluid_statics
P: 127

## pressure liquid

in the derivation of the pressure of liquid, the weight is assumed to act perpendicular to the column of liquid. Plz comment
 Mentor P: 21,652 Gravity pulls straight down, so...
 P: 127 of course but i find similar case to the inclined plane. can somebody give a reasoning?
 Mentor P: 21,652 What do you find similar about an inclined plane? What is YOUR reasoning?
 Mentor P: 40,258 The pressure depends on the depth beneath the surface, which is not slanted. As already stated, the shape of the container--whether slanted or vertical--is irrelevant. If you want more, give a specific example of what you have in mind with a diagram.
 Mentor P: 21,652 Sorry, we don't spoonfeed here. If you want to learn/want help, you need to show some effort at trying to figure it out for yourself. Then when you make a wrong turn, we'll nudge you back in the right direction.
 P: 127 wouldnt this imply that the liquid would accelerate at g in slanted tubes?
Mentor
P: 40,258
 Quote by batballbat wouldnt this imply that the liquid would accelerate at g in slanted tubes?
No. Please describe exactly what you have in mind. Are you talking about hydrostatic pressure? (Which is what I assumed.) Or fluid dynamics?
 Mentor P: 21,652 g is acceleration due to gravity. If you block that acceleration, the required force is f=mg. Aka, weight.
P: 15,294
 Quote by batballbat wouldnt this imply that the liquid would accelerate at g in slanted tubes?
Since you're talking about pressure-at-depth then you're talking about a container full of fluid (as opposed to, say, an air-filled container with an amount of water placed in it).

Water suspended in water is neutrally buoyant, so its not like some arbitrary mass of water is going to start sliding to the bottom, accelerating under gravity.
 P: 127 No. Please describe exactly what you have in mind. Are you talking about hydrostatic pressure? (Which is what I assumed.) Or fluid dynamics? I am not familiar with the terms but i guess you are asking whether i am talking about stationary fluids or flowing ones. Eg. in an inclined plane, there is a mass a top, even though its weight acts exactly downward, it would rather move along the plane. And the force with with it moves along the plane is lesser according to its slope. Same for liquids. But as dave said while the liquid is continuous and stationary, the force with with a finite upper part of liquid exerts on the lower part will be the same as for the case of liquids in vertical column. This is not clear to me. Eg. lets take a column of liquid standing upright and pour some water into it. And then slant it a bit. Then the depth of the liquid increases even though it is not continuous on the upper part (i hope this is understood). So as the depth increases although not uniformly, the pressure in one side must increase. Help me out with this.
 Mentor P: 13,609 Pascal's vases: Another set: Notice that no matter how weird the shape, the tops of the liquid surfaces in the different containers are at the same level. The pressure difference in some container from bottom to top does not depend on shape. It depends only the height of the liquid.
 P: 127 i havent learned any of hydrodynamics or hydrostatics. So i think this phenomenon is taken as as true. Is there a proof for it?
 Mentor P: 13,609 The diagram and image (real) I posted in post #16 are pretty solid evidence. Hydraulic pumps rely on this principle.

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