1. What is the law of conservation of energy?
Lesson link
What is the law of conservation of energy?

2. Draw a line under last lesson’s work and write today’s title in your book...
04/12/2018
c/w
Energy Transfers

3. Developing Explain what is meant by conservation of energy
Learning Objectives
Developing Explain what is meant by conservation of energy
Securing Analyse the changes involved in the way energy is stored when a system changes
Exceeding
Explain that where there are energy changes in a closed system, there is no net change in the energy of that system

4. Engage
For the following slides you need to draw a small diagram of the system and underneath explain the energy transfers involved
System 1: A man pushes a boulder up a steep hill

5. Engage
For the following slides you need to draw a small diagram of the system and underneath explain the energy transfers involved
System 2: A car hits a wall

6. Engage
For the following slides you need to draw a small diagram of the system and underneath explain the energy transfers involved
System 3: A steam engine accelerating due to a constant force

7. Engage
For the following slides you need to draw a small diagram of the system and underneath explain the energy transfers involved
System 4: A motorbike slowing down

8. Engage
For the following slides you need to draw a small diagram of the system and underneath explain the energy transfers involved
System 5: A kettle boiling water

9. ‘Lost’ Energy What does the law of conservation of energy state?
Sometimes we might say some energy is ‘lost’. This isn’t particularly accurate however…
What does the law of conservation of energy state?
So what has actually happened to the ‘lost’ energy?
When a mechanical process is occurring (e.g. like a human running or a motor spinning), there is commonly a rise in temperature.
As such some of the energy provided (from the fuel) gets transferred into thermal/heat energy and sound!

10. Unwanted energy transfer
Here is a perfect example of a system that has unwanted energy transfer. Some of the energy provided by the petrol (total energy) is being dissipated as heat energy which is the wasted energy
The kinetic energy is what we actually want (to move the machine) so this is the useful energy
What could we do to this machine to make sure that we waste less energy as heat?

11. Time to practice… Complete all the questions on the sheet provided.
Make sure to write in full sentences.
E.g.
Question 1: State the law of conservation of energy
Answer: The law of conservation of energy is….

12. Exam Practice
1a) State the equation linking gravitational potential energy, mass, g and height.
(1 mark)
(iii) A motor lifts a 130 g mass to a height of 63 cm. Calculate the gravitational potential energy (GPE) gained by the 130 g mass. (2 marks)
(iv) Why is the amount of GPE gained by the mass less than the amount of electrical energy transferred to the motor? (2 marks)

13. Exam Corrections:
1a) State the equation linking gravitational potential energy, mass, g and height.
(1 mark)
GPE = mass x g x height [1 mark]
(iii) A motor lifts a 130 g mass to a height of 63 cm. Calculate the gravitational potential energy (GPE) gained by the 130 g mass. (2 marks)
130g = 0.13kg and 63cm= 0.63m [1 mark]
GPE= m x g x h GPE= 0.13 x 10 x 0.63m = 0.819J [1 mark]
(iv) Why might the amount of GPE gained by the mass be less than the amount of electrical energy transferred to the motor? (2 marks) ..
Some of the energy provided to the motor will be used to overcome friction leading so some energy being wasted as heat and sound

14. Developing Explain what is meant by conservation of energy
Learning Objectives
Developing Explain what is meant by conservation of energy
Securing Analyse the changes involved in the way energy is stored when a system changes
Exceeding
Explain that where there are energy changes in a closed system, there is no net change in the energy of that system

15. Independent Study
Research and report on the methods used by motor companies to increase fuel efficiency (reduce dissipation of energy as heat) since 1975