At a certain point in a pipeline the water's speed is 4.00 m/s and the gauge pressure is 5.00 x 10^4 Pa. Find the gauge pressure at a second point in the line, 12.0 m lower than the first, if the cross-section area at the second point is twice that at the first.

Answer 1

hints:
1. gauge pressure is zero-referenced against ambient atmospheric pressure, which (usually) cancels out at different points of the pipe if the distance is short.

2. For short distances, we might be able to justify assumption of no frictional loss.

3. Equation of continuity:
V1A1=V2A2

4. Bernoulli equation for incompressible flow:
v²/2+gz+p/ρ = constant