Quote: I just don't see why you think the mass of the fuel can be ignored.
And who said that the mass of the fuel could be ignored? NOBODY! FYI: Density (one of the 3 terms in the applicable equation) is the ratio of mass to volume. The whole point is that the AREA of the fuel line (diameter, effectively) doesn't have any affect on the pressure generated by accelerating the fuel. Also keep in mind that the fuel line is attached to the vehicle and forces generated from acceleration are transferred to the vehicle through the attachment points.
