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Homework Help: Water bottle pressure problem with hole at bottom

  1. Dec 4, 2011 #1
    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. jcsd
  3. Dec 5, 2011 #2

    rude man

    User Avatar
    Homework Helper
    Gold Member

    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.)
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