The pressure at the start of a 180km stainless steel natural gas pipeline is 4MPa and at the end is 2MPa. if the diameter is 0.4m, what will be the gas flow rate through the system? (ignore losses other than friction, ρ= 40 kg/m^3, μ= 11x10^-6 Pa) Could anybody please point me in the right direction on how I actually do this question? I have done questions where we were asked the mass flow rate before but we were not given values for pressure etc in them. I know that i have to use the moody diagram but do not know what to do with the pressure values given. Also came across this formula in my notes: μ = [(∏*d^4)/(128*Q*l)]*(P1-P2) but surely it could not be that easy? Thanks for any help in advance!