Homework Help: Bernoulli's principle

1. Oct 7, 2012

Avalanche

1. The problem statement, all variables and given/known data

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.