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Homework Help: Speed in Larger and Smaller Tube

  1. Nov 30, 2011 #1
    1. The problem statement, all variables and given/known data
    A constricted horizontal tube of radius r1 = 4.00cm tapers to a tube of radius r2 = 2.50cm. If water flows at a speed 3.50m/s in the larger tube, (A) find its speed in the smaller tube. (b) Find the water pressure difference ΔP=ΔP1-ΔP2 in kPa and in atm.

    2. Relevant equations

    I have no clue.

    3. The attempt at a solution

    Succeeded in doing part A.

    A1V1 = A2V2

    V2 = (A1V1)/A2 = (pi(4)^2(3.50)) / (pi(2.50)^2) = 8.96 m/s
    Last edited: Nov 30, 2011
  2. jcsd
  3. Dec 1, 2011 #2

    Simon Bridge

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    Venturi effect?
  4. Dec 2, 2011 #3
    You need to use Bernoulli's principle . The water speeds up and therefore gains KE.
    This gain in KE comes from a decrease in PE (pressure)

    ΔP = 0.5ρ(v2^2 - v1^2) ρ = density of water
    (this is bernoulli's principle in its simplest form with the tube horizontal)
    Last edited: Dec 2, 2011
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