[Oppofeescom]

I was wondering about water pressure and if it is constant according to depth. For example, if we had a cylinder filled with water (let's say for arguments sake 200mm diameter by 10m deep/ high), and a tank filled with water (let's suppose 10m diameter by 10m deep/ high) would the water pressure be equal at the bottom of both vessels?

[UpperMan]

Pressure is a ratio (Force over area), and so is defined by being constant in the two scenarios you described.

Consider a very long thin tube open at both ends plunged from sea level to the bottom of the Mariana's Trench. Would you expect the pressures inside the tube to be different to the pressures outside it?

[infarrelisam]

Imagine a tank with a small tube running up the side that is attached at the lower level. Does the size of the tank affect the liquid level in the tube? Pressure is depth dependent, not volume dependent.

[metropropuskruww]

I think dalton's law covers that.

[Doctorpills]

>>>Imagine a tank with a small tube running up the side that is attached at the lower level. Does the size of the tank affect the liquid level in the tube? Pressure is depth dependent, not volume dependent

There may be some point where the thinness of the tube/vessel has the adhesion of the liquid to the walls starting to reduce the weight of the liquid mass

[CefGemYAffews]

> There may be some point where the thinness of the tube/vessel has the adhesion of the liquid to the walls starting to reduce the weight of the liquid mass

It has to get a few mm across for that to happen. For most tanks the pressure is dependent only on depth.

For another piece of fun, did you know that we weigh less in Australia than in England because the acceleration due to gravity is larger over there? It's quite a significant difference, of the order of 0.1%. Which means that in England the pressure in a water tank at a depth of 10 m is, um, about 200 Pa more.

> PS. "weigh less"

I weigh about 1006 Newtons.

[kjanyeaz1]

For another piece of fun, did you know that we weigh less in Australia than in England because the acceleration due to gravity is larger over there? It's quite a significant difference, of the order of 0.1%. Which means that in England the pressure in a water tank at a depth of 10 m is, um, about 200 Pa more.

Could you explain the mechanics involved here Moll?. I take it this is due to distance from the equator. I had the picture that gravity maintained a constant value.

[flueftArete]

Could you explain the mechanics involved here Moll?. I take it this is due to distance from the equator. I had the picture that gravity maintained a constant value.

As I recall, it varies with the local geology.

[longrema]

As I recall, it varies with the local geology.

So England has denser rock?

[55Beaphable]

Could you explain the mechanics involved here Moll?. I take it this is due to distance from the equator. I had the picture that gravity maintained a constant value.

Damn this flu. Forgot all about the gravity mapping done a couple years ago. Even so, I still find the mechanism somewhat confusing. It is one thing having different readings from a near solid body like the moon, but I wouldn't have thought our mantle would have promoted this size of disparity. Does this indicate something in regards to sub-mantle convection?

[gusunsuth]

http://en.wikipedia.org/wiki/Mass_co...on_(astronomy)

[CathBraun]

>>>It has to get a few mm across for that to happen. For most tanks the pressure is dependent only on depth.

Hence the mention of the exception.

[Noxassope]

does it though with a static head?

[Noilemaillilm]

>>>It has to get a few mm across for that to happen. For most tanks the pressure is dependent only on depth.

Hence the mention of the exception.

For capillarity to come into the equation, you're talking a few microns rather than a few mm.

[FourEsters]

>>For capillarity to come into the equation, you're talking a few microns rather than a few mm.

Probably, didn't state a vessel or tube diameter, someone else did. The temp of the liquid and characteristics of the surface and purety of the liquid [water I think in this case] would have an influence.

For most practical purposes when considering the weight of water as relates to head pressure for flow considerations, pipe drag and other factors are significant.

[Thomas12400]

we are talking of non-flowing water so pipe resistance wont be a factor, or at least i don't think so.

[risyGreeple]

>>>we are talking of non-flowing water so pipe resistance wont be a factor, or at least i don't think so.

Alright, I'll sit back here in the sun and reconcile the stillness of intention ;-), the perfect armchair observer.

[MartZubok]

Does the change of volume of the mass of water with increased temperature change the head pressure? Probably goes to the original question, have us a thought about all those water molecules loosely stacked one above another.

[Muhabsssa]

For static pressure, all you have to remember is

p=rho x g x h where rho = density of fluid and h is height of fluid. If rho, g, or h change, the pressure changes.

[KLhdfskja]

Does the change of volume of the mass of water with increased temperature change the head pressure? Probably goes to the original question, have us a thought about all those water molecules loosely stacked one above another.

rho will decrease, h will increase, so very little change in p (if any)