# Homework Help: Water bottle pressure problem with hole at bottom

1. Dec 4, 2011

### ntsai91

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

Suppose a bottle filled with water, which has a hole close to the bottom
as shown in the figure. Express your answer with y1 , y2, and Po
(atmospheric pressure). Assume A1 << A2.

1) When a cap is closed, find the condition, where no water leaks out form the hole; v1=0

2) Now consider the cap is open, estimate the velocity of the water flowing out from the hole.

2. Relevant equations

P1 + ρgy1 + 1/2 ρv12 = P2 + ρgy2 + 1/2 ρv22

3. The attempt at a solution

1) Zero-d out the two terms with velocity. Got up to

P1 - P2 = ρg (y2-y1)

not sure what the question is really looking for...

2) I got v1 = √(2g(y1-y2)/((A12/A22)-1))

is this right?
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Dec 5, 2011

### rude man

question 1: what are p1 and p2? Your answer must be an expression of one or more of
p0, (y2-y1), A1 and A2.

question 2: how did you arrive at your answer for #2? (It's not what I got.)