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Homework Help: Still lost

  1. Jan 17, 2004 #1
    Here is a problem dont understand:
    A liquid with a density of 1.08*10^3 kg/m^3 flows through two horizontal sections of tubing joined to the end. In the first section the cross sectional areais 10.5 cm^2, the flow speed is 274 cm/s, and the pressure is 1.29*10^5 Pa. In the second section, the cross section area is 2.84 cm^2.
    You are supposed to find the flow speed in the smaller section using:

    (First Pressure)+ (Density*G*(First velocity)^2)= (pressure two)+ (.5*density*(second veloity)^2)

    When I simplify I keep getiing an answer with 2 unknowns (pressure and the second velocity) What am I missing?
     
  2. jcsd
  3. Jan 17, 2004 #2
    If the liquid is incompressible and irrotational or in other words ideal,

    You are missin an Equation
    [tex]A_{small}v_{small}=A_{large}v_{large}[/tex]

    Code (Text):

    NOTE: No. of unknown = No. of Equations
     
  4. Jan 17, 2004 #3
    Here's wat I did:

    I changed evrything to meters and i Knew that the density of water was 1000 kg/m^3

    129000 Pa + (.5 * 1000kg/m^3 * (.274m/s)^2)=

    (second Pressure) + (.5 * 1000 *(2nd Velocity)^2)

    So....
    (133054.104 - (second Pressure))/540 = (Second Velocity)^2
     
  5. Jan 17, 2004 #4
    Thank you
     
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