What happened to the flow rate in this activity?

What happened to the flow rate in this activity?

• A. Stayed constant
• B. Increased
• C. Decreased
• D. Fluctuated

Answer: (A)

Flow rate stays the same when the forces driving the flow and the resistance to flow are kept constant. In a flow system, the rate at which fluid moves is determined by the pressure difference across the system and the resistance it faces (Q is proportional to ΔP divided by R). If you hold the pressure gradient steady (for example, with a fixed pump setting or a fixed height difference) and keep the tube’s properties (radius, length, viscosity) from changing, the flow rate remains unchanged over time. That’s why the activity showed a constant flow rate. If the drive or the resistance had varied, you’d expect the flow rate to increase, decrease, or fluctuate instead.

Flow rate stays the same when the forces driving the flow and the resistance to flow are kept constant. In a flow system, the rate at which fluid moves is determined by the pressure difference across the system and the resistance it faces (Q is proportional to ΔP divided by R). If you hold the pressure gradient steady (for example, with a fixed pump setting or a fixed height difference) and keep the tube’s properties (radius, length, viscosity) from changing, the flow rate remains unchanged over time. That’s why the activity showed a constant flow rate. If the drive or the resistance had varied, you’d expect the flow rate to increase, decrease, or fluctuate instead.