Collisions, energy transfers and conservation
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The teaching part (1 min) is free to watch. A free account opens the whole lecture: 1 worked example, 4 practice questions, 4 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 did the energy go?
- Conservation of energy
Read the transcript of the teaching part
Last time
Before we start: last time, in Upthrust and flotation, you learned these points. Here they are again on one card. Keep them in mind, because today builds on them.
Where did the energy go?
Two lumps of clay collide and stick together. They were moving, and now they move more slowly. Their kinetic energy has gone, yet nothing was destroyed. Energy is never lost, only transferred, and a collision is a perfect place to follow it.
Conservation of energy
The principle of conservation of energy: energy cannot be created or destroyed. It can only be transferred from one form to another. The total energy of a closed system is constant. It does not say that useful energy is conserved. Some energy is always spread out as thermal energy. So conservation lets us find unknown energies: add up what goes in, and what comes out.
How often it comes up
How often Cambridge has asked each part, counted by ExamYard from every past paper in its question bank: Conservation of energy · Energy transfers.
The whole chapter: Work, Energy and Power, Work, Energy and Power.
Chapter 5.1: Energy
- Collisions, energy transfers and conservation 6 min
Also for A Level Physics 9702
Which topics come up most in A Level Physics 9702 past papers, counted from every paper since 2004: Paper 1 topic frequency, Paper 2 topic frequency.