1. The problem statement, all variables and given/known data 2. Relevant equations ρ=789, μ=.0012 3. The attempt at a solution From the energy equation we get hf=0.9 We know that hf=f(L/D)(V^2)/(2g) [sorry don't know how to use latex after they removed the bar on the right] Now I can substitute V for Q, but I'm stuck with f and Q as unknowns and I only have one equation. The solutions manual did something weird : 128μLQ/πρgd^4 It looks like they substituted f for something, but I can't figure out what. I only know how to look up f in the Moody diagram or 64/Re for laminar flow. Did they iterate it somehow?