Viscosity and Poiseuille Flow (4B) Practice Test

A lab compares two Newtonian fluids flowing through the same rigid cylindrical capillary (same $r$ and $L$) under the same pressure drop $\Delta P$. Fluid X has viscosity $\eta_X = 1.0\ \text{mPa}\cdot\text{s}$ and Fluid Y has viscosity $\eta_Y = 4.0\ \text{mPa}\cdot\text{s}$ at the measurement temperature. Flow is laminar for both. Based on Poiseuille flow, what is the expected ratio $Q_X/Q_Y$?

A researcher evaluates whether a capillary-flow assay is sensitive to small manufacturing variation in tube radius. Two nominally identical rigid cylindrical capillaries have the same length $L$ and are used with the same Newtonian fluid at the same temperature and the same applied pressure drop $\Delta P$. Capillary A has radius $r$, while Capillary B has radius $0.90r$. Assuming laminar Poiseuille flow, which outcome is most consistent with the expected change in volumetric flow rate?