Lesson 3: Work, Energy & Power Transformations
Demonstrating understanding of mechanical principles, motion, forces, and energy for NCEA Level 2 Physics.
🎯 Ngā Whāinga Akoranga | Learning Intentions
Work done (W = Fd), Gravitational Potential Energy (E_p = mgh), Kinetic Energy (E_k = 0.5mv^2), Elastic Potential Energy (E_ep = 0.5kx^2), and Power (P = W/t).
Apply conservation of mechanical energy to solve roller coaster and falling object problems, and calculate power output during mechanical work.
🎥 Media Anchor & Pedagogical Scaffold
Work, Energy & Power Conservation Laws
Video Clip: Power & Work Done — Equations and Calculations, by Cognito (Runtime: 4m 29s). Note: this is a UK GCSE resource, not an NCEA one. The work and power equations are the same ones our ākonga use, so it is sound for the physics — but its exam framing is not ours. Use it to teach the concept, not as assessment guidance.
🧠 1. Before Viewing (Activate & Predict)
How is energy transferred from potential storage to kinetic motion without being created or destroyed?
👁️ 2. During Viewing (Watch With a Job)
- State the equations: write the formulas for (1) work done, (2) power, and (3) the link between them. Include SI units for each quantity.
- Calculate: a force of 200 N moves an object 5 m. How much work is done? If this takes 10 s, what is the power output?
- Energy transfer: the video discusses energy transformations. Describe ONE example from the video where kinetic energy is converted to another energy type.
🗣️ 3. After Viewing & Kaiako Move (Process & Apply)
Kaiako Move: Demonstrate a mechanical pendulum, discussing thermal energy loss due to friction and air resistance in real-world systems.
Immediate Task: Complete Section 3 of your Mechanics Portfolio: Mechanical Energy Conservation & Power Output Problem Set.
⚡ Whakaoho | Do Now: Physics Mechanics Recall (10 mins)
The first hill is always the highest. Look at any rollercoaster. No later hill ever exceeds the first.
Two minutes: say why that is not a design choice but a physical requirement. Name the energy the carriage starts with, what it converts to, and what friction takes. Your answer is conservation of mechanical energy, stated before anyone writes the equation.
📖 Activity 1: Mechanical Investigation & Vector Problem Solving (25 mins)
Track the energy (15 min). A 500 kg rollercoaster carriage starts at rest at the top of the first hill (45 m), descends to a second hill (30 m), then a third (12 m). Calculate E_p and E_k at each of the three heights assuming no friction, and confirm the total is constant. Then recompute assuming 15% of the starting energy is lost to friction by the time the carriage reaches the second hill, and state the maximum height the carriage could still reach after that point.
Work and power (10 min). Task A does 6000 J of work in 3 seconds; Task B does the same 6000 J of work in 12 seconds. Calculate the power for each task. State plainly what power measures that work does not, using your two numbers.
📝 Activity 2: Level 2 Physics Portfolio Task & Merit/Excellence Scaffolding (20 mins)
Portfolio — Section 3. Submit: (1) your energy audit at three points, frictionless and with losses; (2) work and power calculations with units; (3) a paragraph explaining the rollercoaster hill rule from conservation of energy.
🏫 Kaiako Planning & Pedagogy Notes
NCEA Level 2 Alignment: Direct preparation for Level 2 Physics (Demonstrate understanding of mechanics). Emphasise linking mathematical working directly to physical concept explanations for Merit/Excellence grades.