Energy stores, conservation and work done
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The teaching part (1 min) is free to watch. A free account opens the whole lecture: 2 worked examples, 6 practice questions, 2 real past-paper questions with the answers explained, the mistakes that lose marks, the full-marks tip, a one-card summary and a quick quiz.
What this lecture covers
- Where does the energy go?
- Energy stores
- Energy transfers
Read the transcript of the teaching part
Last time
Before we start: last time, in Momentum and its conservation, you learned these points. Here they are again on one card. Keep them in mind, because today builds on them.
Where does the energy go?
A cyclist freewheels down a hill and then brakes to a stop. Her energy was not lost. It was moved from one store to another. That idea, that energy is never lost, only moved, is the heart of physics.
Energy stores
Energy is kept in stores. The kinetic store is the energy of a moving object. The gravitational potential store is the energy an object has because of its height. The elastic store is in stretched or squashed things. The chemical store is in food, fuel and batteries. The thermal store is the energy of hot objects. The nuclear store is inside atoms. The unit for energy in every store is the joule, J.
Energy transfers
Energy moves between stores in four ways. By a force doing work: that is a mechanical transfer. By an electric current: an electrical transfer. By heating, from a hotter object to a cooler one. And by waves, such as light and sound, which carry energy through space or matter.
How often it comes up
How often Cambridge has asked each part, counted by ExamYard from every past paper in its question bank: Work · Energy stores and transfers · Work done.
The whole chapter: Energy, Work and Power, Energy, Work and Power.
Chapter 1.7: Energy, work and power
- Energy stores, conservation and work done 5 min
- Gravitational potential and kinetic energy 6 min
- Power and efficiency 6 min
- Energy resources 7 min
Also for O Level Physics 5054
Which topics come up most in O Level Physics 5054 past papers, counted from every paper since 2004.