The flow rate of a liquid is directly proportional to the pressure gradient.

The flow rate of a liquid is directly proportional to the pressure gradient.

• A. Flow Rate Is Inversely Related to the Gradient
• B. Flow Rate Is Directly Proportional to the Gradient
• C. Flow Rate Is Independent of Gradient
• D. Flow Rate Is Proportional to Viscosity

Answer: (B)

Flow through a vessel is driven by the pressure difference between its ends. If that pressure gradient increases while the fluid’s viscosity and the geometry (radius and length) stay the same, the flow rate rises in direct proportion. This relationship is captured by Poiseuille’s law, where the flow rate Q is proportional to the pressure difference ΔP (Q ∝ ΔP). If the gradient is zero, there’s no flow; increase the gradient and the flow increases linearly. Viscosity, radius, and length modulate how much flow actually occurs, with higher viscosity and longer length reducing flow and a larger radius (to the fourth power) greatly increasing it. In cardiovascular terms, this is often summarized as flow being proportional to the pressure gradient divided by resistance (Q ∝ ΔP/R), where resistance itself depends on viscosity, length, and radius. Thus, the statement that flow rate is directly proportional to the pressure gradient is correct.

Flow through a vessel is driven by the pressure difference between its ends. If that pressure gradient increases while the fluid’s viscosity and the geometry (radius and length) stay the same, the flow rate rises in direct proportion. This relationship is captured by Poiseuille’s law, where the flow rate Q is proportional to the pressure difference ΔP (Q ∝ ΔP). If the gradient is zero, there’s no flow; increase the gradient and the flow increases linearly. Viscosity, radius, and length modulate how much flow actually occurs, with higher viscosity and longer length reducing flow and a larger radius (to the fourth power) greatly increasing it. In cardiovascular terms, this is often summarized as flow being proportional to the pressure gradient divided by resistance (Q ∝ ΔP/R), where resistance itself depends on viscosity, length, and radius. Thus, the statement that flow rate is directly proportional to the pressure gradient is correct.