# Comparing hydrostatic forces at the bottom of these 3 containers

• ucody0911
In summary: Yeah, the...In summary, the drawing shows that the water containers sit on the ground, while the third type of water container sits on a fixed support along the X-axis and is suspended in air. The bottom parts of the containers are subjected to hydrostatic forces by the formula F=pgh x A. However, the force on the bottom face of the container in the third case is much less than the forces on the bottom face of the containers in the first and second cases.
ucody0911
Homework Statement
q
Relevant Equations
q
hello all ,
1st and 2 nd water containers sit on ground and 3rd type of water container sit on fixed support along X axis and bottom parts are suspended in air , pls see picture , the drawing is half cross sections of cylinders
All water level heights H and tubes D diameter are same ,
Hydrostatic forces on bottom face of containers , F1 ,F2 ,and F3
by the formula F=pgh x A , F1 and F2 are same , but , i think that F3 is not same , it is much less than F1 and F2 . am i right ? so , how i calculate F3 force ?

#### Attachments

• hydforce.jpg
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What is holding the T piece at the bottom of #3 in place? Or is it in the process of falling?

haruspex said:
What is holding the T piece at the bottom of #3 in place? Or is it in the process of falling?
lets consider 2 cases ,
1. T piece is stationary fixed , welded along x axis
2 . T piece is falling down

ucody0911 said:
lets consider 2 cases ,
1. T piece is stationary fixed , welded along x axis
2 . T piece is falling down

haruspex said:
canceling case of falling ,
just consider , T piece is fixed and stationary

I'm not very sure, but I think the platform of the second container is a cube and we should be given the length of its one more dimension (the one going into the page).

Hall said:
I'm not very sure, but I think the platform of the second container is a cube and we should be given the length of its one more dimension (the one going into the page).

drawing is half cross sections of cylinders ,

ucody0911 said:
drawing is half cross sections of cylinders ,

ucody0911 said:
by the formula F=pgh x A , F1 and F2 are same , but , i think that F3 is not same
Oh, and why is that ?

##\ ##

ucody0911 said:
canceling case of falling ,
just consider , T piece is fixed and stationary

haruspex said:

Hall said:
F1=F2 = pgH x A = 1000 x 9.8 x H x 3.14 x D x D / 4

haruspex said:
question is : is F3 not equal to F1 and F2 ? is less than F1 and F2 ?
"why ? " - just very needs to clarify for this . :)

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Haven't seen your calculation for F3 yet !

##\ ##

BvU said:
Haven't seen your calculation for F3 yet !

##\ ##
so and my question is also for F3 :)

ucody0911 said:
am i right ?
No.

##\ ##

Here's the three central columns:
does this picture ring a bell ?

##\ ##

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Did I miss a post that was quickly removed ?
(I do admit to being male ... )

And I didn't intend to insult @ucody0911 , but apparently caused an explosion nevertheless ...

##\ ##

BvU said:
Did I miss a post that was quickly removed ?
(I do admit to being male ... )

And I didn't intend to insult @ucody0911 , but apparently caused an explosion nevertheless ...
had feeling like that, angry teacher is RINGING BELL in school boy's ear and screaming as "NO " and "WHY " and reminding Newton's or pascal's law , i thought that this forum is not for school boys to help to make their homework , but may be my question is kind of level of school knowledge

Anyway, I'm taking back my words and saying sorry
i just wanted to discuss here :

in my opinion, F3 is not possible to be same equal force to F1,F2 , because there is also hydrostatic fx force on level of X line ,
and i think that if F3 is same with F1 , our energy conservation law saying that it is not possible to be almost doubled hydrostatic force if we consider fx as hydrostatic force

BvU and berkeman
ucody0911 said:
had feeling like that, angry teacher is RINGING BELL in school boy's ear and screaming as "NO " and "WHY " and reminding Newton's or pascal's law
Yeah, the phrase "ring a bell" didn't translate very well into your native language and sayings. In English it just refers to an "Aha" moment, when you finally understand something. Similar to the cartoons you see with a light bulb lighting above a person't head when they finally understand something.

ucody0911 said:
had feeling like that, angry teacher is RINGING BELL in school boy's ear and screaming as "NO " and "WHY " and reminding Newton's or pascal's law , i thought that this forum is not for school boys to help to make their homework , but may be my question is kind of level of school knowledge

Anyway, I'm taking back my words and saying sorry
i just wanted to discuss here :

in my opinion, F3 is not possible to be same equal force to F1,F2 , because there is also hydrostatic fx force on level of X line ,
and i think that if F3 is same with F1 , our energy conservation law saying that it is not possible to be almost doubled hydrostatic force if we consider fx as hydrostatic force
Most unfortunate. In dutch the expression 'lichtje doen branden' has no traumatic connotations. And it translated into 'ring a bell'.

The idea of the picture in #16 was: these columns are exactly identical. Any forces on the sides can only work in a horizontal direction and therefore not exert any contribution in the vertical direction. And for all three we have $$\Delta p = \rho \,g\,\Delta h$$
The composer of the exercise was (is) just trying to confuse you by adding extra stuff on the sides.

All in good spirit !

##\ ##

I need to think about it some more, but it seems like:

(a) the weights of the 3 containers of water are different, since they have different amounts of water in them

(b) the water pressures at the bottom of the 3 water columns need to be the same for the 3 containers, since the water columns are the same heights

(c) the extra support near the bottom of the 3rd container should support most of the weight of that container.

I'm having trouble reconciling these 3 things, but will keep thinking about it...

BvU said:
The composer of the exercise was (is) just trying to confuse you
And this composer apparently is doing a good job !

Tom.G and berkeman
ucody0911 said:
F3 is not possible to be same equal force to F1,F2 , because there is also hydrostatic fx force on level of X line ,
Is your thought that the reaction force to fx (i.e., fx upwards on the water) is helping to support the water, so it needs less support at the bottom? If so, you need to consider all the vertical forces on the water. Those include a downward force from the upper face of the horizontal part of the T.

If you were to add variables for all the different heights and cross sections in the diagrams, you would find that for these forces to add up to balance the weights of water then F1=F2=F3. But of course it is much simpler just to apply the pressure law: at depth H the pressure is ##\rho gH#, so if the bases are all the same area then the forces there are all the same.

Hall

## 1. How do you compare hydrostatic forces at the bottom of different containers?

To compare hydrostatic forces at the bottom of different containers, you need to calculate the pressure at the bottom of each container using the formula P = ρgh, where P is pressure, ρ is density, g is the acceleration due to gravity, and h is the height of the liquid column. The container with the highest pressure at the bottom will have the highest hydrostatic force.

## 2. What factors affect the hydrostatic forces at the bottom of a container?

The hydrostatic forces at the bottom of a container are affected by the density of the liquid, the acceleration due to gravity, and the height of the liquid column. The shape and size of the container may also play a role in the distribution of hydrostatic forces.

## 3. How does the shape of a container affect hydrostatic forces at the bottom?

The shape of a container can affect hydrostatic forces at the bottom by changing the distribution of pressure. For example, a container with a wider base will have a larger surface area at the bottom, resulting in a larger hydrostatic force. A container with a narrower base will have a smaller surface area at the bottom, resulting in a smaller hydrostatic force.

## 4. Can the hydrostatic force at the bottom of a container be greater than the weight of the liquid?

Yes, the hydrostatic force at the bottom of a container can be greater than the weight of the liquid. This can occur when the liquid is under high pressure or when the container has a large surface area at the bottom. In this case, the container may experience a net upward force, known as buoyancy, which can be greater than the weight of the liquid.

## 5. How do you measure hydrostatic forces at the bottom of a container?

Hydrostatic forces at the bottom of a container can be measured using a pressure gauge or by calculating the pressure at the bottom using the formula P = ρgh. The weight of the liquid and the dimensions of the container may also need to be measured in order to accurately determine the hydrostatic force.

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