How does the reference height affect Bernoulli's principle calculations?

Click For Summary

Homework Help Overview

The discussion revolves around the application of Bernoulli's principle and how the choice of reference height impacts the calculations. Participants are examining the relationship between pressure, height, and velocity in fluid dynamics.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants are exploring how different reference heights affect the calculations of pressure using Bernoulli's equation. There is a focus on the implications of setting reference heights at different points, such as the manometer versus the beer level in a container.

Discussion Status

Some participants have provided insights regarding the relationship between the heights involved in the problem, noting that the difference in height must remain consistent regardless of the reference point chosen. The discussion is ongoing, with various interpretations of the reference height being considered.

Contextual Notes

There is a mention of a specific height difference of 2 meters that must be maintained, regardless of the reference height chosen. Participants are questioning the implications of this requirement on their calculations.

Avalanche
Messages
23
Reaction score
0

Homework Statement


Please click on the following link for the solution.

http://s1292.photobucket.com/albums...ew&current=Bernoullisequation_zps0d4485d7.jpg

Homework Equations



P1 + .5(rho)v12 + (rho)gy1 = P2 + .5(rho)v22 + (rho)gy2


The Attempt at a Solution



P1 = 101300 Pa
y1 = 0
rho = 1015 kg/m^2
v1 = 0.1*10^-2 m/s
P2 = ?
y2 = 2.0 m
v2 = 0.5 m/s

Plugging numbers into bernoulli's principle

P2 = 101300 + .5(1015)(0.1*10^-2)2 + 0 - .5(1015)(.5)^2 - 1015*9.8*2
P2 = 81281.66Pa

But according to the textbook, the answer is 120,800 Pa. I get that answer when y1 = 2.0 and y2 = 0. I don't understand how the reference height could be at P2 could be at 0 because if it was, shouldn't P2 be denoted as P1?

Any help would be appreciated.
 
Physics news on Phys.org
The height at the manometer is two meters LESS than the height at the beer level. No matter what you use as the reference height, y1 - y2 = 2 m.
 
So for this question, the reference height of 0 is already set at the manometer? Is it possible to use the reference height at the beer level in the container?
 
As I said, the "zero" level can be anywhere, but you must have y1 - y2 = 2 m.
 

Similar threads

Replies
6
Views
2K
Replies
3
Views
2K
  • · Replies 1 ·
Replies
1
Views
6K
  • · Replies 1 ·
Replies
1
Views
3K
Replies
2
Views
4K
  • · Replies 6 ·
Replies
6
Views
6K
Replies
4
Views
4K
Replies
2
Views
27K
  • · Replies 6 ·
Replies
6
Views
4K
  • · Replies 10 ·
Replies
10
Views
3K