ENERGY

1. 1 ENERGY THE ABILITY TO CAUSE CHANGE

2. 2 Types of Energy mechanical energy

3. 3 types of energy • Thermal energy - due to temperature (recall that this comes from the motion of molecules, so it is really kinetic energy) • Heat energy -transfer of thermal energy • Chemical Potential Energy - stored in chemical bonds • Nuclear energy - stored in the nuclei of an atom • Electrical energy - EM interactions • Radiant energy -carried by EM waves

4. 4 Energy CLIP • Energy is the capacity (ability) to do work.  • Kinetic Energy: Associated with an object in motion • Potential Energy: Present in an object that has the potential to move because of its position

5. 5 Kinetic Energy • Motion • KE of an object depends upon two variables: • the mass (m) of the object • the speed (v) of the object.

6. 6 Calculating Kinetic Energy A formula to find the kinetic energy of any body based on its velocity.

7. 7 Potential Energy • An object can store energy as the result of its position.

8. 8 Forms of potential energy Gravitational Elastic Chemical -position above the Earth’s surface -stored in something stretchy -chemical reaction

9. 9 Gravitational Potential Energy • GPE is the energy stored in an object as the result of its vertical position (i.e., height). • Amt. of GPE is dependent on two variables: • the mass • the height

10. 10 Calculating Gravitational Potential Energy GPE = mgh

11. 11 Elastic Potential • Elastic PE is the energy stored in elastic materials as the result of their stretching or compressing.

12. 12 Conservation of Energy

13. 13 Conservation of Energy Energy cannot be created or destroyed…only changed from one form to another. The total energy of an isolated system remains constant (isolated systems have no external forces and no mass changes)

14. 14 ENERGY BEFORE = ENERGY AFTER Energy can be changed from one form to another, but it does not disappear.

15. 15 Mechanical Energy • The motion of some objects contain a combination of only kinetic and potential energies. • ME is the sum of the KE and forms PE associated with a system • Therefore, ME= KE + PE

16. 16 Conservation of Energy TOTAL ENERGY OF THE SYSTEM REMAINS THE SAME

17. 17 Conservation of Energy TOTAL ENERGY OF THE SYSTEM REMAINS THE SAME

18. 18 Conservation of Mechanical Energy: • Therefore, • MEi = MEf • KEi + PEi = KEf + PEf • ½mvi2 + mghi = ½mvf2 + mghf

19. 19 Conservation of Mechanical Energy: • Conservation of ME only hold true when the only energies of the system are KE and PE. • Therefore, in the presence of friction energy is transformed to other types of energies.

20. 20 Energy Conversion When one type of energy is changed or transformed into another type of energy

21. 21 Examples Steam Engine Lighting a Match Battery Can you think of More? Create a graphic organizer to illustrate energy conversions. draw a picture to represent four different energy conversion you may encounter in everyday life. Be sure to explain what type of energy it starts with and what type of energy it ends with.

22. 22 Energy Conversion clip

23. 23 What about a falling object? What happens when it hits the ground? Where did the energy all go?

24. 24 Energy Conversions of a dropped object • As it is falling and when the object hits the ground the energy is converted into other types of energy such as: • sound energy (waves), Light Energy (sparks), thermal energy due to friction (heat) in the ground and air, vibrations in the earth (energy waves.) • If the object bounces, some energy is converted momentarily into elastic potential energy.

25. If Robin Hood had been Written by an Engineer....    And Robin didst slowly and with great determination put potential energy equal to the work of his muscles into an elastic storage device.                                                                              And therewith Robin the Bold and Valiant didst convert this stored energy most quickly, efficiently, and accurately into the velocity of a sturdy and pointed dart (oft called arrow) such that almost all of its former potential energy didst become kinetic. Then this speedy dart didst split an arrow (oft called dart) already buried in most distant target, having been previously hurled there at an equally great speed by a similar conversion of stored energy. 25

26. EOCT Questions Which statement about energy is true? A Energy can be increased in a closed system. B Energy cannot be conserved. C Energy can be decreased in a closed system. D Energy cannot be created nor destroyed.