2. Energy Makes things happen. Takes many different forms and changes readily from one form to another.

3. Energy Makes things happen. Takes many different forms and changes readily from one form to another. Active Energy – effects easily seen or detected. -

4. Energy Makes things happen. Takes many different forms and changes readily from one form to another. Active Energy – effects easily seen or detected. - Kinetic energy (E k – the energy of an object when its moving)

5. Energy Makes things happen. Takes many different forms and changes readily from one form to another. Active Energy – effects easily seen or detected. - Kinetic energy (E k – the energy of an object when its moving) - Light energy

6. Energy Makes things happen. Takes many different forms and changes readily from one form to another. Active Energy – effects easily seen or detected. - Kinetic energy (E k – the energy of an object when its moving) - Light energy - Heat energy

7. Energy Makes things happen. Takes many different forms and changes readily from one form to another. Active Energy – effects easily seen or detected. - Kinetic energy (E k – the energy of an object when its moving) - Light energy - Heat energy - Sound energy

8. Potential energy Forms of energy which are stored and only have an effect when they are changed to active energy (E p )

9. Potential energy Forms of energy which are stored and only have an effect when they are changed to active energy (E p ) - Chemical potential energy – changed to active energy by chemical reactions.

10. Potential energy Forms of energy which are stored and only have an effect when they are changed to active energy (E p ) - Chemical potential energy – changed to active energy by chemical reactions. Food, fuels, and explosives contain chemical potential energy.

11. Potential energy Forms of energy which are stored and only have an effect when they are changed to active energy (E p ) - Chemical potential energy – changed to active energy by chemical reactions. Food, fuels, and explosives contain chemical potential energy. - Elastic potential energy – energy stored when a material is stretched or compressed.

12. Potential energy Forms of energy which are stored and only have an effect when they are changed to active energy (E p ) - Chemical potential energy – changed to active energy by chemical reactions. Food, fuels, and explosives contain chemical potential energy. - Elastic potential energy – energy stored when a material is stretched or compressed. It is changed to active energy when the tension is released.

13. Potential energy Forms of energy which are stored and only have an effect when they are changed to active energy (E p ) - Chemical potential energy – changed to active energy by chemical reactions. Food, fuels, and explosives contain chemical potential energy. - Elastic potential energy – energy stored when a material is stretched or compressed. It is changed to active energy when the tension is released. - Gravitational potential energy – energy that is gained when something is lifted up.

14. Potential energy Forms of energy which are stored and only have an effect when they are changed to active energy (E p ) - Chemical potential energy – changed to active energy by chemical reactions. Food, fuels, and explosives contain chemical potential energy. - Elastic potential energy – energy stored when a material is stretched or compressed. It is changed to active energy when the tension is released. - Gravitational potential energy – energy that is gained when something is lifted up. This energy is changed to active energy when the object falls down.

15. Potential energy - Electrical energy – energy that is stored in a power source (battery).

16. Potential energy - Electrical energy – energy that is stored in a power source (battery). This energy is changed to active energy when the circuit is switched on.

17. Potential energy - Electrical energy – energy that is stored in a power source (battery). This energy is changed to active energy when the circuit is switched on. - Nuclear energy – energy that is stored in a nucleus.

18. Potential energy - Electrical energy – energy that is stored in a power source (battery). This energy is changed to active energy when the circuit is switched on. - Nuclear energy – energy that is stored in a nucleus. Changed to active energy in nuclear reactors or atomic bomb explosions.

19. Energy All forms of energy are measured in joules (symbol J)

20. Energy All forms of energy are measured in joules (symbol J) One joule is a very small amount of energy, so kilojoule is often used kJ – 1000J = 1kJ

21. Questions: 1. Give an example of something that has: a) Increasing kinetic energy b) Decreasing heat energy c) Decreasing chemical potential energy d) Increasing elastic potential energy e) Decreasing gravitational potential energy

22. Questions: 2. What type of energy is stored in: a) An unlit firework? b) An inflated balloon? c) A hamburger? d) A battery? e) A child at the top of a playground slide?

23. Gravitational potential energy All to do with the height of an object – when height of an object changes, its gravitational potential energy changes.

24. Gravitational potential energy All to do with the height of an object – when height of an object changes, its gravitational potential energy changes. E p = mg h

25. Gravitational potential energy All to do with the height of an object – when height of an object changes, its gravitational potential energy changes. E p = mg h Where E p is the increase in gravitational potential energy in joules (J)

26. Gravitational potential energy All to do with the height of an object – when height of an object changes, its gravitational potential energy changes. E p = mg h Where E p is the increase in gravitational potential energy in joules (J) M = mass in kg of the object being lifted

27. Gravitational potential energy All to do with the height of an object – when height of an object changes, its gravitational potential energy changes. E p = mg h Where E p is the increase in gravitational potential energy in joules (J) M = mass in kg of the object being lifted G = strength of gravity, 10N kg -1

28. Gravitational potential energy All to do with the height of an object – when height of an object changes, its gravitational potential energy changes. E p = mg h Where E p is the increase in gravitational potential energy in joules (J) M = mass in kg of the object being lifted G = strength of gravity, 10N kg -1 h = change in height, in metres

29. Example A 5kg object is lifted to a height of 2m above the floor it was resting on. 1. Calculate the gain in gravitational potential energy on the object.

30. Example A 5kg object is lifted to a height of 2m above the floor it was resting on. 1. Calculate the gain in gravitational potential energy on the object. 2. How much gravitational potential energy does the object lose if it is dropped and falls back down to the floor?

31. Example 1 and 2 have the same answer. Ep = mg h = 5 x 10 x 2 = 100J

32. Example 1 and 2 have the same answer. Ep = mg h = 5 x 10 x 2 = 100J Object is lifted 2m off the floor. Gain in gravitational potential energy = 100J (g = always 10) so 10x10

33. Example 1 and 2 have the same answer. Ep = mg h = 5 x 10 x 2 = 100J Object is lifted 2m off the floor. Gain in gravitational potential energy = 100J (g = always 10) so 10x10 The object has 100J more gravitational potential energy when 2m off the floor

34. Example 1 and 2 have the same answer. Ep = mg h = 5 x 10 x 2 = 100J Object is lifted 2m off the floor. Gain in gravitational potential energy = 100J (g = always 10) so 10x10 The object has 100J more gravitational potential energy when 2m off the floor The object falls 2m. Loss in gravitational potential energy is 100J

35. Formula E p 10m h

36. Question Khyati and her mother go up in a lift. Khyati’s mass is 45kg and she gains 5400J of gravitation potential energy as she goes up in the lift. Calculate the height Khyati gains. Kyhati’s mum gains 7800J GPE. Calculate her mass.

37. Important use of GPE Hydroelectric power – water stored behind a dam has GPE.

38. Important use of GPE Hydroelectric power – water stored behind a dam has GPE. The water goes through an exit at the top of the dam and drops to the bottom of the dam

39. Important use of GPE Hydroelectric power – water stored behind a dam has GPE. The water goes through an exit at the top of the dam and drops to the bottom of the dam As the water falls, GPE is changed into kinetic energy

40. Important use of GPE Hydroelectric power – water stored behind a dam has GPE. The water goes through an exit at the top of the dam and drops to the bottom of the dam As the water falls, GPE is changed into kinetic energy At the bottom of the dam, the kinetic energy is changed to electrical energy by the turbines of the power station.

41. Questions 1. Calculate the GPE a boy of mass 75kg gains if he climbs 50 steps, each step having a height of 20cm 2. A girl, mass 55kg, jumps off a bridge into the water below. The bridge is 2.5m above the water, Calculate the GPE the girl lost when she hits the water.