# Bernoulli's principle

1. Oct 7, 2012

### Avalanche

1. The problem statement, all variables and given/known data
Please click on the following link for the solution.

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

2. Relevant equations

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

3. 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.

2. Oct 7, 2012

### voko

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.

3. Oct 7, 2012

### Avalanche

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?

4. Oct 7, 2012

### voko

As I said, the "zero" level can be anywhere, but you must have y1 - y2 = 2 m.