Pressure Temp Volume: Relationship & Practice Qs

[bfusco]

Homework Statement

i am just reviewing for a test and doing some practice questions. i disagreed with one of the answers and now i am uncertain about the relationships between pressure volume and temp. i thought the relationships were:

as pressure increases, temp increases, volume decreases (any combo of these three)
as pressure decreases, temp decreases, volume increases (any combo of these three)

and just incase these are correct and maybe I am interpreting the question wrong, the questions is basically given a picture of piping varying in size, at which point in the pipe is the water under the least pressure.

i thought i would be at the point of largest volume, but the answer according to my teacher is a point with the least volume.

 

[gneill]

Is the water stationary or moving? Water is essentially incompressible so it doesn't behave like a gas with regards to pressure and volume, and volume versus temperature change is pretty small as long as it remains liquid. For moving gases or fluids the pressure is related to the velocity; you need to be concerned with Bernoulli's equation.

 

[bfusco]

according to the solutions sheet, the pressure is at its lowest at the thinnest part of the pipe, i thought it would be at the widest part of the pipe (greater diameter).

and yes the water is moving

 

[NascentOxygen]

Search google images for venturi meter