Horizontal Tube Speed

Hypnos_16

1. Homework Statement

Seawater flows through a horizontal tube of diameter 3.00 cm that is joined to a second horizontal tube of diameter 1.70 cm. The pressure difference between the tubes is 7.25 kPa. What is the speed of flow in the first tube?

2. Homework Equations

I thought it was P1 + 1/2 pv2
turns out it isn't

3. The Attempt at a Solution

i don't know if it's cause i'm stressed, or just missing something, i cannot get this question to work.

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edgepflow

Note: P1 + 1/2 p v1^2 = constant = P2 + 1/2 pv2^2.

Do you also need to apply the conservation of mass ?

Hypnos_16

The conservation of mass? and what "Constant" are you talking about there?

edgepflow

The conservation of mass will allow you to relate the speed of the fluid in the two different size pipes and the pipe diameter.

Bernoulli's equation says P + p v^2 / 2 + p g h = constant. So if you know these values at one point, you know them at the other.

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