1. Energy Continued
Unit 5 – Lecture 2

2. Review: PE & KE Potential Energy – “stored” E
Kinetic Energy – energy of motion / “released” E

3. Conservation of Energy
Law of Conservation of Energy:
energy can neither be created nor destroyed in normal reactions
energy can be changed in form from one to another
initial energy = final energy
energy in = energy out
aka 1st law of thermodynamics

4. Mechanical Energy Mechanical E – total amount of PE & KE in a system
as PE decreases, KE increases
as PE increases, KE decreases
what kind of relationship is this…direct or inverse?

5. Mechanical Energy Equation: MEinitial = MEfinal
(PE + KE)initial = (PE + KE)final
(m g h + ½ m v2 )initial = (m g h + ½ m v2 )final

7. Mechanical Energy
ME in a pendulum:

8. Practice
At which point…
is GPE at a maximum?
why?
is KE at a maximum?

9. Practice Which of these describes E? [any]
Ability to do work Ability to cause change
Ability to increase energy Ability to decrease work
Joules is NOT a unit for which of these?
PE KE
Force Work

10. Forms of Energy Mechanical Energy
energy of an object due to its motion [kinetic E] or position [potential E]

11. Forms of Energy Electromagnetic E waves of mostly invisible E
light energy often is converted into thermal E
can be converted into chemical E through photosynthesis

13. Forms of Energy Chemical E
stored and released in the bonds between atoms
food, batteries

14. Forms of Energy Nuclear E
stored and released from the nucleus of an atom

15. Forms of Energy Thermal E heat in all its forms and flows
recall – exothermic & endothermic
transferred through conduction, convection, & radiation

16. Forms of Energy Electrical E separation and movement of electrons
[not really a form of E on its own – it is a combination of forms of Mechanical and Electromagnetic E]

17. Practice
When you are watching tv, what energy conversions are taking place?
Which energy transformation takes place when a match is struck against the side of a matchbox and bursts into flames?
What causes you to hear something? What kind of energy is sound?