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 and work done — equations and calculations for NCEA Level 2 Physics (Cognito) (Runtime: 4m 29s).
🧠 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). For a rollercoaster with three given heights, calculate E_p and E_k at each point assuming no friction, and confirm the total is constant. Then recompute with 15% lost to friction and state the maximum height the carriage could still reach.
Work and power (10 min). Calculate the work done and the power for two given tasks — same work, different times. 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.