1. THE ABILITY TO CAUSE CHANGE
ENERGY
THE ABILITY TO CAUSE CHANGE

2. Relate transformations and flow of energy within a system-chemical, mechanical, electromagnetic, light, sound, thermal, electrical, and nuclear.
Goals
Identify energy transformations within a system (e.g. lighting of a match).
Sound

3. Types of Energy
mechanical energy

4. Heat energy -transfer of thermal energy
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

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

6. Potential and Kinetic Energy

7. How tall should they make they make the 1st hill?
Question
An amusement park wants to build a new roller coaster. They want the 2nd hill to be 65m tall.
How tall should they make they make the 1st hill?
What information do we still need?

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

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

10. Unit for Energy (add everything in blue to 1st page)
The Joule (J) is the SI unit of Energy.
The calorie is another common unit for energy
Where does this come from?
(KE = ½ m v2)
1J= 1N●m

11. Example Problems Kinetic Energy (KE = ½ m v2)
1) The velocity of a car is 65 m/s and its mass is 2515 kg. What is its KE?
2) If a 30 kg child were running at a rate of 9.9 m/s, what is his KE?

12. Practice Problems
IN THIS ORDER….
Page 2: #s 6, 7, 8, 5

13. Potential Energy
An object can store energy as the result of its position.
Clip

14. Potential and Kinetic Energy
Click photo

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

16. 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

17. Calculating Gravitational Potential Energy
GPE = mgh

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

19. Conservation of
Energy

21. 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)

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

23. Conservation of Energy

24. Conservation of Energy TOTAL ENERGY OF THE SYSTEM REMAINS THE SAME
Tutor Vista Activity
(click)

25. TOTAL ENERGY OF THE SYSTEM REMAINS THE SAME
Conservation of Energy
KEi + PEi = KEf + PEf
TOTAL ENERGY OF THE SYSTEM REMAINS THE SAME

26. Conservation of Mechanical Energy:
KEi + PEi = KEf + PEf
Problem: A student lifts his 2.0 kg pet rock 2.8 m straight up. He then lets it drop to the ground.
Calculate the following:
How much Potential Energy does it have at the top (before he drops it).
How much Kinetic Energy does it have at the top (before he drops it).
After it is dropped, how
much KE will it have when
it is 1.4 m above the ground?
Total=54.88
54.88 = PEf + KEf
54.88 = mgh + KEf
54.88 = (2) (9.8)(1.4) + Kef
54.88 = KEf
27.44 J = KEf
54.88 J
0 J

27. 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.

28. Tutor Vista Activity
(click)

29. Examples 21 Lighting a Match Steam Engine Battery
Can you think of More?
ENERGY PROJECTS

31. What happens when it hits the ground? Where did the energy all go?

32. 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.

33. 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
D Energy cannot be created nor destroyed.

34. Wile E Coyote & Roadrunner Clip