Comparing hydrostatic forces at the bottom of these 3 containers

[ucody0911]

Homework Statement

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Relevant Equations

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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 ?

 

[haruspex]

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

 

[ucody0911]

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

 

[haruspex]

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

Then what are your answers for the two cases (and why)?

 

[ucody0911]

Then what are your answers for the two cases (and why)?

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

 

[Hall]

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).

 

[ucody0911]

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 ,

 

[Hall]

drawing is half cross sections of cylinders ,

Can you please show me your calculations for $F_2$?

 

[BvU]

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 ?

$\$

 

[haruspex]

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

Ok, so what is your answer for that case, and why?

 

[ucody0911]

Ok, so what is your answer for that case, and why?

Can you please show me your calculations for $F_2$?

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

 

[ucody0911]

Ok, so what is your answer for that case, and why?

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

 

[BvU]

Haven't seen your calculation for F3 yet !

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[ucody0911]

Haven't seen your calculation for F3 yet !

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so and my question is also for F3 :)

 

[BvU]

am i right ?

No.

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[BvU]

Here's the three central columns:

does this picture ring a bell ?

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[BvU]

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 ...

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[ucody0911]

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

 

[berkeman]

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.

Thanks for deleting your post.

 

[BvU]

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 !

$\$

 

[berkeman]

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]

The composer of the exercise was (is) just trying to confuse you

And this composer apparently is doing a good job !

 

[haruspex]

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.