Types – Kinetic – energy of motion Mechanical – done by machines

2. Types – • Kinetic – energy of motion • Mechanical – done by machines • Potential – stored energy (gravitational or elastic/flexed solids) • Chemical – found in the bonds between atoms

3. Thermal – heat or internal kinetic energy • Sound – vibrations in matter carried on waves • Light – electromagnetic radiation • Electrical – moving and static electrical charges • Nuclear – found within the nucleus of atoms

4. Work – a force exerted during a distance. • W = F*d • Work and Energy… You must have energy to do work. • Unit is Joules (J)

5. 230N 1 m An acorn attempting to lift 230N (about 50 lbs.) one meter must pull with a force equal to the weight of the barbell. How much work has he done? W = F*d W = 230N * 1m W = 230 Unit? J Joules

6. 230N 2.5m • How much work to raise the bar over his head to the height of 2.5 m? * • W= 230N*2.5m • W= 575J • If we doubled the weight to 460N, what happens to the amount of work? It would double as well! Directly Proportional *If his arms were long enough!

7. F distance • Work is a vector, which means it has a direction. • Work can only be done if the force and distance directions are the same. NO WORK DONE!!!

8. Amount of work done per the amount of time it takes to do it. Work done (J) Power = Time (s) Unit of power = J/s = 1 watt (W) 1 kilowatt (kW) = 1000 W

9. Essential Question: • What is the relationship between potential energy and kinetic energy?

10. 1st Law of Thermodynamics: • Energy can be changed from one form to another, but NOT destroyed. • Change of energy: the final energy is equal to the beginning energy. • The ultimate source of ALL energy on Earth IS?

11. Gravitational • PE g = mass * gravity * height • Higher an object = ____PE • Greater the mass = ____PE • Greater gravity = ____PE • Elastic • PE elastic= weight x distance stretched • Greater the weight = ____PE • Greater the distance stretched = ____PE

12. KE = ½ mass * velocity2 • The more massive the object = ____KE • The faster the object = ____KE • Why does velocity have a greater role in KE than mass? The mass is cut in half but the velocity is squared!

13. The final energy is equal to the beginning energy.

14. KEi + PEi= KEf + PEf • In other words, the sum total of KE +PE before and after some kind of transformation MUST be equal.

15. Entropy – a change of a useable form of energy into an unusable form… HEAT (thermal energy) • Whenever energy is “lost” it is ALWAYS converted into HEAT.

16. Distance has to be in ______. • Force has to be in _______. • How do you change kg to N? • Time has to be in ______. • Mass has to be in ________. • Velocity has to be in _____. • How do you change W to kW? meters Newtons x10 seconds kilograms m/s /103

17. The bow stores potential energy in its bent limbs when drawn. • This energy is transformed into kinetic energy as the arrow is released. • PE of the bow = KE of arrow • PE & KE = work the archer had to use to draw the bow

18. Even though the arrow is now at rest (no KE) and the bow is not drawn (no PE), NO ENERGY HAS BEEN DESTROYED! • The target did “Work” to the arrow by bringing it to rest with friction… • Whenever energy is “lost” it is ALWAYS converted to HEAT.

19. What would happen to the depth of penetration if the arrow were moving faster? • What happens to the speed of the arrow when shot from a “stiffer” (harder to draw) bow? • What happens to the speed of the arrow if it weighs more? • What happens to the speed of the arrow if it is longer? (bow pushes it for a longer distance)

20. w w KE PE F d P h t mg ½m v2 PE (J) Power (W) Work (J) KE (J) Work and energy have the same unit!