Why is water unable to flow from A and B to C in a branching pipe system?

[foo9008]

Homework Statement

what does the author mean by if P is below the surface of B then h2 and Q2 are both 0 ?

Homework Equations

The Attempt at a Solution

at the last second line from the bottom , the author gave if P is below the surface of B then water must be out of B and Q1 +Q2 = Q3 ? both statement are contrary to each other

 

[haruspex]

h₂ might be a typo for d₂?
It might help if you would define L_i and d_i. Q_i is volume flow rate, I gather.

 

[foo9008]

h₂ might be a typo for d₂?
It might help if you would define L_i and d_i. Q_i is volume flow rate, I gather.

which h₂ is typo for d₂ ?

 

[haruspex]

which h₂ is typo for d₂ ?

In your post, you quoted a line from the second attachment referencing h2. There is no other h2 in either attachment. I am suggesting the h2 in the attachment might be a typo for d2.

 

[foo9008]

In your post, you quoted a line from the second attachment referencing h2. There is no other h2 in either attachment. I am suggesting the h2 in the attachment might be a typo for d2.

what does h2 mean actually ? why it will = 0 ?

 

[haruspex]

what does h2 mean actually ? why it will = 0 ?

I don't know, but I might be able to figure it out if you answer the questions I posed in post #2.

 

[foo9008]

refrerring to the notes in post 1 , the author said that when P is above the surface of the resevoir B , then water must flow into B and Q1= Q2 + Q3 , why can't the the water from A and B flow to C ?, which is Q1 +Q2 = Q3 ?

 

[haruspex]

refrerring to the notes in post 1 , the author said that when P is above the surface of the resevoir B , then water must flow into B and Q1= Q2 + Q3 , why can't the the water from A and B flow to C ?, which is Q1 +Q2 = Q3 ?

Imagine closing off the point where the three pipes meet for the moment, so nothing is flowing. The pressure on the A side of that point will exceed the pressure on the B side. So when the joint is opened to allow flow, the A side will win.
This all assumes no drag in the pipes. In the real world, some drag and a narrow pipe on the A side could mean that when water flows there is a large drop in pressure from the A reservoir to the junction, allowing water to enter the junction from B.