# Fluids and viscous flow

1. Nov 5, 2007

### maos

1. The problem statement, all variables and given/known data
Water (n = 1.00 10-3 Pa·s) is flowing through a horizontal pipe with a volume flow rate of 0.029 m3/s. As the drawing shows, there are two vertical tubes that project from the pipe. From the data in the drawing, find the radius of the horizontal pipe.

2. Relevant equations

Q = πR^4(P1-P2) / 8nL

3. The attempt at a solution

0.029 = πR^4(0.045) / (8*10^-3 * .7)

solve for R, multiply by 100. However, i dont get the right answer...

What am i doing wrong? this seems like such a straightforward problem

2. Nov 5, 2007

### Staff: Mentor

Is the differential pressure, (P1 - P2), in the formula given as the head (height or depth) of water (0.045 m), or is it pressure, in which case $\Delta$P = $\rho$g$\Delta$h, where $\Delta$h is the difference in heights of the water columns, i.e. 0.045 m.

3. Nov 5, 2007

### maos

oh maybe it's pgh. let me give it a second go.

4. Nov 5, 2007

### maos

yes i got it right. thank you Astronuc for the fast reply! I owe you :)