1. KINETIC KINETIC ENERGY

2. If an object is moving: • It is capable of doing work • It has energy Kinetic Energy (KE) is the energy of motion

3. Since Kinetic Energy is the energy of motion it depends on both: • Mass of the object • Speed(velocity) of the object KE = 1 Mass x Velocity2 2 Or… M(V)2 2

4. The mass of an object kinetic energy • The speed of an object the kinetic energy However one has more impact on kinetic energy. Which variable is it and why?

5. Example: Ms. May throws a tennis ball at the rainbow and kitten cloud forming over Ms. Hart’s head. Mass of ball = 5kg Speed of ball = 80 m/s KE = 5 x 802 = 5 x 6,400= 32,000 = 16,000J 2 2 2

6. Increase Mass Defeated by the cloud of happiness, Ms. May picks up and throws a tennis ball with more mass. Mass of ball = 10kg (doubled) Speed of ball = 80 m/s KE = 10 x 802 = 10 x 6,400 = 64,000 = 32,000J 2 2 2 Ms. May Ms. May Ms. May Ms. Hart

7. Increase Speed Just then… a unicorn appeared in the cloud and with all of its magical powers of happiness and love, Ms. May decided that the only way to crush Ms. Hart’s cloud of joy was to throw the original tennis ball with more speed! Mass of ball= 5kg Speed of ball = 160 m/s (doubled) KE = 5 x 1602 = 5 x 25,600 = 128,000 = 2 2 2 64,000J

8. Energy Conversions Energy conversion is a change from one form of energy to another • Any form of energy can change into any other form of energy • Energy can change into multiple forms

9. Types of Energy Can you give an example of an energy conversion?

10. Examples • Light (radiant) energy from sun chemical energy in our food kinetic energy in our bodies 2. Solar cells change light energy electrical energy

11. 3. A car engine burns gasoline, converting the chemical energy in gasoline mechanical energy.

12. Roller Coaster Conversion PE KE and KE PE

13. Friction Anytime one form of energy is converted into another form, some of the original energy always gets converted into thermal energy due to friction! • Thermal energy due to friction not useful energy • Cannot be used to do work! • During energy conversion, some energy converted to thermal energy due to friction E1 E2 TE

14. Conservation of Energy • When we use energy, it doesn’t disappear. • Energy changes form, but the total amount of energy in the universe stays the same. The Law The law states that energy cannot be created or destroyed but can be changed from one form to another

15. Another look at the energy conversions in a section of roller coaster track: M.E. M.E. M.E. KE KE KE PE PE PE

16. Ending Height ???? Law of Conservation of Energy says: M.E. of car at A =M.E. of car at C M.E. atAandC is all Potential Energy, so… weight x height at A = weight x height at C Weight of the car is the same (it’s the same car) so… The heights must also be the same. Starting height = Ending height! A C B Starting Height

17. But in Reality… As the car rolls along the track, some of its original mechanical energy (P.E. + K.E.) converted to HEAT ENERGY(Thermal Energy)because of FRICTION. Ending Height A C B Starting Height

18. So…what really happens is something like this: M.E. M.E. M.E. Ending Height KE KE KE PE PE PE H.E. H.E. H.E. Starting Height

19. M.E. M.E. M.E. Ending Height KE KE KE PE PE PE H.E. H.E. H.E. Starting Height So….the roller coaster car will never be able to get back up to its original height….. …..Unless you add more energy to it!