Which statement about the relationship between pressure and flow is most consistent with the observed results?

Which statement about the relationship between pressure and flow is most consistent with the observed results?

• A. Flow decreases as pressure increases.
• B. Flow increases quadratically with pressure.
• C. Flow increases linearly with pressure.
• D. Flow is independent of pressure.

Answer: (C)

Flow is driven by the pressure gradient across a pathway, and when the resistance the flow faces remains essentially fixed, the flow rate changes in direct proportion to that pressure difference. This yields a linear relationship, described by Q = ΔP / R, so as pressure rises, flow increases in a proportional, straight-line way. The observed linear increase fits this simple, fixed-resistance picture, making it the best description of the data. If flow increased only with the square of pressure, that would suggest the resistance is changing with pressure or the system behaves nonlinearly, which isn’t indicated by a straight-line relationship. If flow were independent of pressure, there would be no driving force linking the two. If flow decreased as pressure increased, that would imply an opposing factor, also inconsistent with a driving pressure gradient.

Flow is driven by the pressure gradient across a pathway, and when the resistance the flow faces remains essentially fixed, the flow rate changes in direct proportion to that pressure difference. This yields a linear relationship, described by Q = ΔP / R, so as pressure rises, flow increases in a proportional, straight-line way. The observed linear increase fits this simple, fixed-resistance picture, making it the best description of the data.

If flow increased only with the square of pressure, that would suggest the resistance is changing with pressure or the system behaves nonlinearly, which isn’t indicated by a straight-line relationship. If flow were independent of pressure, there would be no driving force linking the two. If flow decreased as pressure increased, that would imply an opposing factor, also inconsistent with a driving pressure gradient.