Water flows through a pipe of diameter 10 cm at 2 m/s. The pipe narrows to 5 cm diameter. Find the speed in the narrow section and the volume flow rate. Step 1: Areas scale as diameter squared: A₁/A₂ = (10/5)² = 4. Step 2: Continuity: v₂ = v₁(A₁/A₂) = 2 × 4 = 8 m/s. Step 3: Volume flow rate Q = A₁v₁ = π(0.05)² × 2 = π × 0.0025 × 2 ≈ 0.0157 m³/s (≈ 15.7 litres/s). Answer: 8 m/s in the narrow part; 0.0157 m³/s everywhere. Halving the diameter quadruples the speed.