Lesson 3: Hydrodynamics of Waka Hourua: Buoyancy, Drag & Displacement
Exploring physical phenomena—waves, forces, vectors, optics, and relativity—through traditional Polynesian navigation and ocean science.
🎯 Ngā Whāinga Akoranga | Learning Intentions
Archimedes' principle of buoyancy (), displacement hulls, hydrodynamic skin friction and form drag, and double-hull stability physics.
Calculate buoyant force and hull displacement volume, test streamlined vs blocky hull shapes in a water channel, and measure drag resistance forces.
🎥 Media Anchor & Pedagogical Scaffold
How do ships float? Buoyancy! — learnbiologically
Video (1 min, learnbiologically): An explanation of how ships float and the physics of buoyancy, including how Archimedes' principle applies to vessel design and why different hull shapes matter.
🧠 1. Before Viewing (Activate & Predict)
Why are traditional double-hulled waka hourua exceptionally stable and fast in heavy Pacific seas?
👁️ 2. During Viewing (Watch With a Job)
Watch the full 14-minute clip and record evidence for these core buoyancy concepts:
- Archimedes' Principle: How does the weight of water displaced relate to an object's buoyant force?
- Floating equilibrium: What determines whether an object sinks, floats, or stays submerged?
- Density and vessel design: Why can a steel ship float while a steel bar sinks?
- Practical hull design: How do shape and volume affect how much weight a ship can carry?
🗣️ 3. After Viewing & Kaiako Move (Process & Apply)
Kaiako Move: Set up a water trough with spring balances to measure drag force on different carved model hull shapes.
Immediate Task: Complete Section 3 of your Navigation Physics Logbook: Archimedes Buoyancy & Drag Analysis Sheet.
⚡ Whakaoho | Do Now: Steel Sinks. Steel Ships Float.
Two minutes: write the one sentence that resolves that contradiction, then say what you would measure to test whether you are right.
The answer is about displaced water rather than about the material — and it is the same principle that lets a loaded waka hourua carry people and provisions across weeks of open ocean.
📖 Activity 1: Displacement, Then Shape Against Drag
Measure displacement (13 min). Find the volume of water displaced by three hulls of different shape but equal mass. Calculate buoyant force with Fb = ρ V g. Equal mass means equal buoyant force at flotation — check whether your three measurements agree, and if they do not, say which measurement you trust least and why.
Tow them (12 min). Pull a streamlined hull and a blocky hull through the water channel at the same speed, measuring the force needed for each. Then say which kind of drag dominates at that speed: skin friction along the wetted surface, or form drag from shoving water aside.
📝 Activity 2: Navigation Physics Logbook & Problem Solving (20 mins)
Portfolio Section 3. Submit: (1) displacement volumes and buoyant-force calculations for three hulls; (2) your drag measurements with the towing speed stated; (3) an explanation of why a double hull is more stable than a single hull of the same total volume, using the terms centre of mass and lever arm.
🏫 Kaiako Planning & Pedagogy Notes
Year 10 Curriculum Alignment: NZ Curriculum Science Phase 4 — Physical World & Earth/Space Systems. Integrates traditional Polynesian wayfinding (Mātauranga Waka) with foundational NCEA Level 1 Physics mechanics, wave behaviour, and optics.