Fluids rate of flow homework help

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Homework Help Overview

The discussion revolves around a problem involving two cylindrical pipes carrying an ideal fluid in laminar flow. Participants are tasked with calculating the cross-sectional areas and flow rates of the pipes based on given dimensions and velocities.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning, Problem interpretation

Approaches and Questions Raised

  • Participants explore the relationship between flow rate, cross-sectional area, and velocity, questioning the definitions of variables such as a1 and a2. There is confusion regarding the formulas and their application, particularly in relation to the flow rate and the units involved.

Discussion Status

The discussion is active, with participants attempting to clarify their understanding of the equations and the physical concepts involved. Some have made calculations for the cross-sectional areas, while others are questioning the correctness of their interpretations and the implications of their results.

Contextual Notes

There is mention of potential confusion regarding the definitions of variables and the units used in the problem. Participants are also considering the significance of their answers in terms of significant figures.

domyy
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Homework Statement



Two cylindrical pipes both carry an ideal fluid (zero viscosity) in laminar flow. Pipe A has radius Ra = 2 and flow velocity Va = 8cm/s. Pipe B has radius Rb = 4cm and flow velocity Vb = 4cm/s.

A) Calculate the cross section of pipe A and pipe B.
B) Calculate the rate of flow in liters/second (1l = 1000cm cubic)

Homework Equations



maybe v1a1 = v2a2 ?

The Attempt at a Solution



v1a1 = v2a2
= (8cm/s)(2cm) = (4cm/s)(4cm) = 1 ?

It`s wrong.
 
Last edited:
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okay. Now tell me what is a1, a2?
 


domyy said:

Homework Equations



maybe v1a1 = v2a2 ?
Just what do a_1 and a_2 represent?

Also, are these pipes connected end to end, or are they in parallel?
 


you mean...
 
Last edited:


What has pressure got to do with it?

Go back to your first equation: what is a_1? This is not a trick question.
 


I have to calculate cross section of pipe A and B.

My book says cross-sectional area is VA.

I am confused with these formulas because I have the following:

Flow rate = VA
Flow rate = V/T

So, flow rate = cross sectional area = VA?
 
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R = 2 = area 1 = 4
R = 4 = area 2 = 16
?
 
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I think I know it...
 
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would that be correct?
 
  • #10


I just need this to finish my homework.
 
  • #11


I think I know it:

I think I am supposed to use pi. So, could it be: 3.14 x 4^2 = 50.24 for cross section pipe B?
 
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  • #12


I know the answer! I got the answer! I got the answer! Just a question: how should I leave the flow rate considering the answer for B = 0.20096, should I say the answer is 0.20 or 0.200 l/s ?
 
  • #13


domyy said:
I have to calculate cross section of pipe A and B.

My book says cross-sectional area is VA.
Assuming V is volume and A is area, something is wrong, either the book or your reading of it. The units are odd, too: \mathrm{L}^5. If V and A mean something else, then I don't know.

I am confused with these formulas because I have the following:

Flow rate = VA
Flow rate = V/T
What is T?

So, flow rate = cross sectional area = VA?
Think units. What units must flow rate have?
 
  • #14


domyy said:
I know the answer! I got the answer! I got the answer! Just a question: how should I leave the flow rate considering the answer for B = 0.20096, should I say the answer is 0.20 or 0.200 l/s ?
Since the problem, as you gave it, uses only one significant figure, then your answer should have no more than one significant figure.
 

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