this is not a homework problem, its a practical problem for a system i'm working on, but its looks pretty much like a homework problem so posting here. 1. The problem statement, all variables and given/known data Assume a 100 gallon tank is filled with water, constantly filled and pressurized by a pump to 1000psi Assume a hydraulic powered motor which operates with intake required at 300psi, flow of 10 gallons per minute. Can the problem of stepping down the pressure and fixing the flow at 10 gallons per minute be solved by having a pipe connecting the tank to the motor of a given diameter, or a valve at the tank end, where the pipe is of fixed diameter, say 1"? The tank and the and motor are in close proximity, the pipe can be set to the length required. How generally to determine the diameter required? Is the length of the pipe relevant? Or is there some other step required to fix both the pressure and flow between the tank and motor? 2. Relevant equations No sure. 3. The attempt at a solution Flummoxed. I assume there is a relationship between pressure in the pipe and resistance to flow provided by the hydraulic motor. I know I can adjust raise pressure in the pipe by opening the value at tank end and/or using a smaller diameter pipe, but I'm not sure how/if its possible to control both pressure and flow independently as I'd guess they are related as in electricity flow, viz V=IR which in this case I'd guess would be something like pressure = flow x resistance, or Flow = Pressure/Resistance or something like that, but not really sure of units and the like.