How Do You Calculate the Radius of a Pipe in Fluid Mechanics?

[maos]

Homework Statement

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.

Homework Equations

Q = πR^4(P1-P2) / 8nL

The Attempt at a Solution

0.029 = πR^4(0.045) / (8*10^-3 * .7)

solve for R, multiply by 100. However, i don't get the right answer...


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

 

[Astronuc]

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.

 

[maos]

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

 

[maos]

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