When the flow tube radius increased, _______.

When the flow tube radius increased, _______.

• A. Flow rate increased and pressure remained the same
• B. Resistance increased and pump rate decreased
• C. Pressure decreased significantly
• D. Resistance decreased and pump rate increased to maintain pressure

Answer: (D)

Increasing the radius of a flow tube lowers its resistance to flow dramatically, because resistance is inversely related to the fourth power of the radius (R ∝ 1/r^4). With a given driving pressure, a drop in resistance lets more fluid pass, so the flow rate rises. If the system is set up to keep the pressure steady, the pump must increase its rate to maintain that pressure as the tube becomes easier to push fluid through. In short, larger radius → lower resistance, and to sustain the same pressure, the pump rate must rise. This aligns with saying resistance decreases and pump rate increases to maintain pressure.

Increasing the radius of a flow tube lowers its resistance to flow dramatically, because resistance is inversely related to the fourth power of the radius (R ∝ 1/r^4). With a given driving pressure, a drop in resistance lets more fluid pass, so the flow rate rises. If the system is set up to keep the pressure steady, the pump must increase its rate to maintain that pressure as the tube becomes easier to push fluid through. In short, larger radius → lower resistance, and to sustain the same pressure, the pump rate must rise. This aligns with saying resistance decreases and pump rate increases to maintain pressure.