Fluid Flow in a Pipe: G-Greater, L-Less, E-Equal

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Homework Help Overview

The discussion revolves around fluid dynamics, specifically analyzing the relationships between pressure and velocity at different points in a pipe carrying a non-viscous incompressible fluid. The original poster presents several statements regarding pressure and velocity comparisons at various points in the system.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • The original poster attempts to apply Bernoulli's Equation and the Continuity Equation to reason through the relationships between pressure and velocity at different points in the pipe. They express confusion regarding the role of gravity in affecting fluid velocity.

Discussion Status

Some participants provide feedback on the original poster's reasoning, indicating that most of the comparisons seem reasonable, while questioning specific statements. There is a call for clarification regarding the implications of the Continuity Equation on velocity comparisons.

Contextual Notes

Participants emphasize the importance of showing effort before receiving assistance and discourage providing complete solutions to maintain a focus on learning.

hellblazer970
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Homework Statement


Use the picture as a guide. P is the pressure in the pipe, and vi is the speed of a non-viscous incompressible fluid at locations i = 1,2,3,4,5.(For each statement select G-Greater than, L-Less than, or E-Equal to).
prob07_Bernoulli.gif


A) P1 is ... P4
B) v1 is ... 2v3
C) P4 is ... P5
D) P1 is ... P2
E) v4 is ... v5
F) P3 is ... P4
G) v1 is ... v2

Homework Equations


Bernoulli's Equation p + .5ρv^2 + ρgy
Continuity Equation: A2*v2=A2*v2

The Attempt at a Solution


A) P1 < P4 because P1 has a higher velocity, so pressure must decrease to compensate.
B) v1 > 2v3, if the diameter is doubled, the velocity is quadrupled as per continuity equation
C) P4 > P5 due to gravity (ρgy)
D) P1 > P2 due to gravity
E) v4 > v5, if v4 has more pressure, it has higher velocity
F) P3 < P4 due to gravity
G) v1 > v2, since P1 has a higher pressure it has a higher velocity

Is my reasoning correct, or do I have something backwards? I guess my main confusion is what effect gravity has on velocity of flow?
 
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Those all look good to me except for E and G.

What does the Continuity Equation say about the velocities?
 
The answers to this question are as follows:

[Moderation Note: Complete solution removed. Hootenanny ][/color]

stevebo
 
Last edited by a moderator:
Stevebo said:
The answers to this question are as follows:...

Stevebo,

Please don't give direct answers to questions, that doesn't help people learn!

Please read the section on "Homework Help" here:
https://www.physicsforums.com/showthread.php?t=5374
In particular:
On helping with questions: Any and all assistance given to homework assignments or textbook style exercises should be given only after the questioner has shown some effort in solving the problem. If no attempt is made then the questioner should be asked to provide one before any assistance is given. Under no circumstances should complete solutions be provided to a questioner, whether or not an attempt has been made.
 

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