Pressure due to a Liquid on container Wall

• SpectraPhy09
In summary, the conversation revolves around determining the average pressure on a cuboidal or triangular shaped container, with different calculations being presented and discussed. It is clarified that the average pressure on a flat surface is the total force on the surface divided by the total area, with the geometric center being at h/2 for a rectangular surface and at h/3 for a triangular surface. Further clarification and corrections are made about the calculations for determining Pavg on the triangular wall.

SpectraPhy09

Homework Statement
What is the average pressure on the triangular wall by the liquid ?
given :
density of liquid p
gravitational acc is g
For Dimensions of container please check the figure(i have attached please Check)
.( Assume Patm = 0)
Relevant Equations
Pressure at a point, x distance below the free surface of the liquid = pgx
I have just started this topic so i Don't have much clearity about it .
In our school it was tought that
Pavg = (Pi + Pf)/2 ...(i)
If we have a cuboidal shape container then it should be pgh/2 ryt ?

But also Pavg = Ftotal on the wall /A ...(ii)
= (pgh²l/2)/lh = pgh/2

It it was a triangular wall then Pavg comes different

Using (i) Pavg = pgh/2
(ii) Pavg = pgh/3

Which is correct ?

Using

Attachments

• Screenshot_2021-11-02-10-21-00-120.jpeg
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SpectraPhy09 said:
Ftotal on the wall /A ...(ii)
= (pgh²l/2)/lh
How do you get that for the total force?
And are you saying lh is the area?

@haruspex
Total force on a container wall
= Pressure at geometrical centre × Area of the Surface Or Pavg × Area
For Cuboidal Container
Geometric centre is at h/2 from surface
P = pgh/2
Area = l × h
F = pgh²l/2
For Triangular Surface shaped Container
Geometric centre is at centroid i.e h/3 from surface
P = pgh/3
A = h×l/2

SpectraPhy09 said:
Geometric centre is at h/2 from surface
Not so.

The average pressure on a flat surface is the total force on the surface divided by total area of the surface. What is the total area of the surface that you are interested in? Do you know how to determine the total pressure force on this surface?

Chestermiller said:
The average pressure on a flat surface is the total force on the surface divided by total area of the surface. What is the total area of the surface that you are interested in? Do you know how to determine the total pressure force on this surface?
Yes got it now
I was finding Pavg on the triangular wall

What I could do is this -

There's a correction in the image
Pavg = (pglh^2/6)/(lh/2) = pgh/3
now is it correct ?

haruspex said:
Not so.
But why? For a rectangular surface isn't the Geomecal center at h/2?

1. What is pressure due to a liquid on a container wall?

Pressure due to a liquid on a container wall is the force exerted by the weight of a liquid on the walls of a container. This pressure is caused by the weight of the liquid molecules pushing against the container walls.

2. How is pressure due to a liquid on a container wall calculated?

The pressure due to a liquid on a container wall can be calculated using the formula P = ρgh, where P is the pressure, ρ is the density of the liquid, g is the acceleration due to gravity, and h is the height of the liquid column.

3. What factors affect the pressure due to a liquid on a container wall?

The pressure due to a liquid on a container wall is affected by the density of the liquid, the height of the liquid column, and the acceleration due to gravity. The shape and size of the container may also have an impact on the pressure.

4. What are the units of pressure due to a liquid on a container wall?

The units of pressure due to a liquid on a container wall are typically expressed in Pascals (Pa), which is equivalent to 1 Newton per square meter (N/m²). Other common units include pounds per square inch (psi) and atmospheres (atm).

5. How does the pressure due to a liquid on a container wall change with depth?

The pressure due to a liquid on a container wall increases with depth. This is because the weight of the liquid above a certain point increases as the depth increases, resulting in a higher pressure being exerted on the container walls. This relationship is linear, meaning that the pressure increases at a constant rate with depth.