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

AI Thread Summary
The discussion centers on how the choice of reference height impacts calculations using Bernoulli's principle. The user attempts to solve for P2 using given values but arrives at a different answer than the textbook. It is clarified that the reference height can be set anywhere, but the difference in height (y1 - y2) must remain constant at 2 meters. The confusion arises from whether P2 can be considered at a height of zero, as this affects the pressure calculations. Ultimately, understanding the reference height's flexibility is crucial for accurate application of Bernoulli's equation.
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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.
 
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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.
 
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