Flow in Tubes

Why narrow vessels matter so much

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Poiseuille's law: flow $\propto r^4\,\Delta p$.
• Narrowing a vessel by 16% halves its flow.
• Blood slows in capillaries because their total area is huge.
• Surfactant keeps the lungs’ tiny air sacs from collapsing.

Steps

1. Poiseuille’s law
2. Half the radius
3. A narrowing artery
4. Slowing down in capillaries
5. Widening a vessel
6. Bubbles in the lungs