Lesson P1.1 Changes in energy stores WS: 1.2 MS: 2c, 4a AQA spec link: 1.1.1 A system is an object or group of objects. There are changes in the way energy is stored when a system changes. Students should be able to describe all the changes involved in the way energy is stored Aiming for Grade 4 LOs: State some examples of energy stores. the processes that can transfer energy from one store to another. Identify changes in some energy stores using simple examples. Lesson Starters Off like them to Check
AQA spec link: 5.2 When a force causes an object to move through a distance work is done on the object. So a force does work on an object when the force causes a displacement of the object. The work done by a on an object can be calculated using the equation: work done = force × distance (moved along the line of action of the force) [W = F s ] work done W in joules (J) force F in newtons (N) distance s in metres (m) One joule of work is done when a force of one newton causes a displacement of one metre. 1 joule = 1 newton metre. Students should be able to describe the energy transfer involved when work is done. Work done against the frictional forces acting on an object causes a rise in the temperature of the object. Aiming for Grade 4 LOs: State that energy is measured in joules (J). Calculate the work done by a force. Measure the work done by a experimentally. Lesson Overview Starters Defining work (5 min) Students define the terms work and working as used in common language. Lead them to the idea of a force being involved in working. Forces and energy (10 min) Ask students to describe some situations forces cause changes in energy stores. They should explain what factors would affect the size of changes in these stores. Main Doing work (40 min) Build on the previous idea of forces causing changes in energy stores to introduce the idea of doing work on something. Be careful with the definition here – it is very specific as opposed to the general term work, with which the students will be familiar. Students should perform a few calculations to embed the equation. Students then carry out the practical, including supporting calculations. There will be considerable errors in the experiments, which the students should discuss. Discuss the heating effect of frictional forces using the examples. These can be supported by practical demonstrations such as hand rubbing, bicycle brakes, and so on. Plenaries Resources Practical: Doing work. Interactive: Mathematical work out. Aiming for Grade 6 LOs: Describe the action of frictional forces on objects and the associated heating effect. Use the equation for work done to calculate distances or size of forces. Use repeat values to measure the work done by a experimentally. Aiming for Grade 8 LOs: Use the principle of conservation of energy and forces to explain why objects become heated by frictional forces. the equation for work done in a wide range of contexts.
Working or not? (5 min) Hold a heavy weight but do not lift or drop it. Ask if mechanical work is being done on the weight, and if not, why energy is being transferred as you hold it. Mathematical work out (10 min) Students use the interactive to answer some additional questions involving the equation for work done. Evaluate in detail an experiment to measure work done, explaining why there is variation in the measurements. Lesson P1.4 Gravitational potential energy stores WS: 1.2 MS: 1a, 1c, 3b, 3c AQA spec link: 1.1.2 The amount of gravitational potential energy gained by an object raised above ground level can be calculated using the equation: g.p.e. = mass × gravitational field strength × height [Ep = m g h] gravitational potential energy Ep in joules, J Aiming for Grade 4 LOs: State the factors that affect the change in the gravitational potential energy store of a system. Calculate the gravitational potential energy store of a system using the weight of an object and its height. Measure the gravitational potential energy store changes in a system with a simple practical activity. Lesson Starters Lifting by a things energy energy
AQA spec link: 1.2.2 The energy efficiency for any energy transfer can be calculated using the equation: efficiency = useful output energy transfer total input energy transfer Students should be able to describe ways to increase the efficiency of an intended energy transfer. Aiming for Grade 4 LOs: Describe an efficient transfer as one that transfers more energy by a useful process. State that the efficiency of an energy transfer is always less than 100%. Calculate the efficiency of a simple energy transfer. Lesson Overview Starters Staying on (5 min) Ask students to explain why some electrical devices of the same type (e.g., two different models of last longer than others even though they use the same batteries. Efficiency (10 min) Ask students what is efficiency and why is it wanted? What are the advantages of an efficient device? Form students into groups and ask them to agree on a simple description of what efficiency is and why it is important. Main Investigating efficiency (40 min) Recap the systems used for measuring quantities, particularly the joule and newton as these are required later.Discuss input and output energy in terms of how much energy is transferred from the starting stores into the stores we want it to be. This leads to calculations of efficiency based on these values. Students should try a few of the calculations to ensure that they can do them. Explain the limits to efficiency, linking this to the law of conservation of energy. Students try an efficiency measurement using the practical. Ensure that they are calculating work done correctly and finding the energy supplied to Resources Practical: Investigating efficiency. Interactive: Car efficiency. Aiming for Grade 6 LOs: Calculate the efficiency of a of energy transfers. Use the law of conservation of energy to explain why efficiency can never be greater than 100%. Investigate the efficiency of a Aiming for Grade 8 LOs: Describe design features that can be used to improve the efficiency of an energy transfer. Rearrange the efficiency equation to find input or total output energy. Evaluate in detail an efficiency investigation to justify conclusions.