1. Power and electrical power 12 March 2016 Keywords: Power, Energy, Weight, Force Objectives Understand what power is and be able to calculate it. HSW: AF5 – Working critically with evidence AF4 – Using investigative approaches Used before in: lesson 1 – work Will use again in: PLTS: Team workers – Work collaboratively with others. Used before in: Science AWill use again in:

2. Outcomes All students should be able to describe what makes an object powerful or not. Most students should be able to define power and use the equation. Some students should be able to evaluate practical work and describe how to make it more valid and reliable.

3. Powerful cranes Which is the most powerful crane? Explain why.

4. How is power calculated? The power exerted by an object can be calculated using one of two equations: Time is measured in seconds (s). Power is measured in watts (W). Work done is measured in joules (J). work done time taken power = Remember that work done = energy transferred.

5. A lawnmower engine does 10 kJ of work in 10 seconds. What is the power of the engine? Calculating power question 1 = 1,000 W = 1 kW power = work done time = 10,000 / 10

6. A car transfers 12 mJ of energy in 2 minutes. What is the power of the car? Calculating power question 2 = 100,000 W = 100 kW = 12,000,000 / 120 power = work done time = energy transfer time

7. Power, work and time calculations

8. Anagrams

9. And finally – we find out – who are more powerful – boys or girls? Force x distance = energy Energy/time = power Boys:Girls: ForceDist for 1 rep repsTotal dist worktimepowerForceDist for 1 rep repsTotal dist worktimepower Skipping Lifting Push ups Analysis: What conclusion can you draw? Evaluation: was the evidence reliable? Explain.

10. EnergyGravitationalWatts HeatPowerKinetic Electrical 1 Joule per second Joules

11. Plenary - Multiple-choice quiz