Finding pressure at narrow end of segment

  • Thread starter Thread starter sona1177
  • Start date Start date
  • Tags Tags
    Pressure
Click For Summary

Homework Help Overview

The problem involves a horizontal pipe that tapers from a larger cross-sectional area to a smaller one. The original poster provides initial conditions, including pressure and speed at the larger end, and expresses confusion about using different equations to find the pressure at the narrow end.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants discuss the application of Bernoulli's equation and question the meaning of variables used by the original poster, particularly the term "d." There is also a focus on the lack of information regarding the change in cross-sectional area and the implications of the horizontal orientation of the pipe.

Discussion Status

The discussion is ongoing, with participants seeking clarification on the original poster's approach and terminology. Some guidance has been offered regarding the relevance of potential energy in this context and the correct interpretation of the variables in the equations being used.

Contextual Notes

There is a noted absence of information about the change in cross-sectional area, which is critical for applying Bernoulli's principle correctly. The original poster has clarified that the pipe tapers from 50 cm² to 5 cm², which may influence the discussion further.

sona1177
Messages
171
Reaction score
1

Homework Statement


A horizontal segment of pipe tapers from a cross-sectional area of 50.0 cm^2. The pressure at the larger end of the pipe is 1.20 x 10^5 Pa and the speed is .040 m/s. What is the pressure at the narrow end of the segment?


Homework Equations


I know how to do the problem using Bernoulli's equation but why can't I manage to get the correct answer using P=rho(g)(d). where rho=1000, g=9.8, and d=.00798 m


The Attempt at a Solution


 
Physics news on Phys.org
Could you explain what d is in your equation.
As the pipe is horizontal there is no potential energy consideration.
I also note that there is no information given about the change in the cross section area.
Maybe you could clarify the question?
 
Stonebridge said:
Could you explain what d is in your equation.
As the pipe is horizontal there is no potential energy consideration.
I also note that there is no information given about the change in the cross section area.
Maybe you could clarify the question?

d is the length of the narrow segment which I obtained by dividing area/pi and taking the sq root to get the radius. I then multiplied that by 2.
 
Stonebridge said:
Could you explain what d is in your equation.
As the pipe is horizontal there is no potential energy consideration.
I also note that there is no information given about the change in the cross section area.
Maybe you could clarify the question?

Ooops! Sorry about leaving that info out. It tapers from 50-> 5 cm^2
 
I don't quite understand what you are doing here.
The expression ρhg in the Bernoulli formula includes the terms
ρ the density of the fluid
g acceleration due to gravity
h the height of the liquid above the reference level
You have written ρdg but stated that d is "the length of the narrow segment". However, your calculation looks like it is for the diameter of the narrow segment.
Neither of these values, length or diameter, are the ones in the expression.
As the tube is horizontal, you don't need this term anyway, you just need the terms
½ρv² and p to find the pressure.
The value of v is found from the volume flowing per second being equal in both parts of the tube.
 

Similar threads

  • · Replies 7 ·
Replies
7
Views
1K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 4 ·
Replies
4
Views
5K
  • · Replies 7 ·
Replies
7
Views
3K
Replies
3
Views
2K
  • · Replies 12 ·
Replies
12
Views
3K
  • · Replies 6 ·
Replies
6
Views
5K
Replies
5
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 11 ·
Replies
11
Views
2K