8th grade PE and KE introDUCTION FOR STUDENTS

LECTURE

1. ENERGY

2. Table of Contents How is work, power and energy related? What is energy? 2 types Kinetic Potential 2 types Gravitational Elastic

3. Table of Contents What are other forms of energy? Mechanical Thermal Electrical Chemical Nuclear Electromagnetic

4. Work, Power and Energy What is WORK? Work is done on an object when the object moves in the same direction that the force was applied. Lifting your book bag Work= Force (N) x Distance (m) 1Nm = 1J What is POWER? The rate at which work is done. Running vs walking with your book bag Power= work (J) / time (s) 1J/s = 1W

5. Work, Power, Energy Energy: The ability to do work or cause a change. Whenever work is done energy is transferred to that object. Power is the rate at which the energy is transferred . What do YOU think the unit for energy is? JOULES YAY!

6. Two Types of Energy Kinetic Energy Potential Energy

7. Kinetic Energy “The moving energy”

8. Kinetic Energy Kinetic Energy increases as mass and velocity increase

9. Kinetic Energy

10. Kinetic Energy Velocity is squared Would velocity have the same, less or more of a effect than mass on the kinetic energy of an object? MORE

11. Kinetic Energy Example 1. Determine the kinetic energy of a 625-kg roller coaster car that is moving with a speed of 18.3 m/s. 2. If the roller coaster car in the above problem were moving with twice the speed, then what would be its new kinetic energy?

12. An object can have energy even when its not moving! Stored energy based off of the objects shape or position

13. Potential Energy Energy is stored or held in readiness Book on your desk Apple hanging from a tree Pulling back a rubber band If the apple stays in the tree, it will keep the stored energy due to its height above the ground. If the apple falls, that stored energy of position is converted to energy of motion.

14. Types of Potential Energy Gravitational Potential Energy (GPE) Elastic Potential Energy

15. Gravitational Potential Energy (GPE) GPE: The potential energy related to an objects position above earths surface. Lifting your book on top of your desk = the work you did to lift it Distance the book was moved: height Force you used to lift it: weight

16. Gravitational Potential Energy (GPE) Gravitational Potential Energy increases as weight and height increase.

17. Gravitational Potential Energy (GPE) To calculate GPE use this equation. On Earth the acceleration of gravity is 9.8 m/s 2 and has the symbol g (in this equation)

18. Changing Gravitational Potential Energy (GPE) The Gravitational potential energy of an object can be increased by increasing the height. If the objects are at the same height then what? The object with the larger mass would have more gravitational pull.

19. Elastic Potential Energy Elastic Potential Energy: potential energy associated with objects that can be stretched or compressed. Pulling back a rubber band Winding up a toy

20. Elastic Potential Energy The rubber band has elastic potential energy here because it has been stretched and is storing its energy. If you let the rubber band go, it sails across the room. As it flies through the air it has kinetic energy due to its motion.

21. Remember this! Energy comes in MANY different forms!!!!

22. Mechanical Energy What is Mechanical Energy? Motion Position Mechanical = Potential + Kinetic

23. Examples Potential Kinetic Mechanical

24. If the kinetic energy of a falling apple is 5.2J and its mechanical energy is 8.7J what is its potential energy?

25. Potential = Kinetic Kinetic = Potential Mechanical Energy To sum up… An object with mechanical energy can do work on another object! The more mechanical energy an object has the more work it can do! Law of Conservation of Energy Energy can neither be created nor destroyed; rather, it transforms from one form to another.

26. Thermal Energy All objects are made up of particles called _____ and _________. These particles are always in motion. What kind of energy would they have? Kinetic These particles are arranged in specific ways in different objects What kind of energy would they have? Potential atoms molecules

27. Thermal Energy Total potential and kinetic energy of the PARTICLES in a object is called Thermal Energy!

28. Electrical Energy What do you think this is? Again this is energy of particles! The energy of tiny charged particles called….. Lets think of some examples.... ELECTRONS!!!!

29. Chemical Energy Chemical compounds are made up of _____ and _________. Bonds hold these atoms and molecules together. These bonds have Chemical Energy!!!! Chemical energy can be released when these bonds break!!! atoms molecules

30. Chemical Energy Chemical Potential Energy: energy that is stored in chemical bonds Energy is stored in the bonds that hold carbon and hydrogen atoms together The atoms are released when gas is burned C H H H H

31. Nuclear Energy Potential or Kinetic? Where is the energy stored? NUCLEUS ! When is the energy released? NUCLEAR REACTIONS! 2 kinds Nuclear Fission Example? Nuclear Fusion Example?

32. Electromagnetic Energy Travels in waves Does anyone know what waves are? These waves have… Electr ical properties Magnetic properties What are some examples that we know of that use waves to transfer energy? Electromagnetic!

33. Kinetic Potential Gravitational Elastic Electromagnetic Nuclear Thermal Electrical Chemical Mechanical