Notes 12 – Forms of Energy Part 1

1. Notes 12 – Forms of Energy Part 1

2. States of Energy • Energy exists in two basic states: 1. potential 2. kinetic • Potential energy is stored energy • Kinetic energy is motion energy • Potential and kinetic are NOT OPPOSITES

3. What is Potential Energy? • Stored energy that must be released • Energy that could be used to do work but isn’t yet • It is energy an object has because of: • its position: book held above your head • its shape: stretched rubber band • Or its condition: charged battery

4. What is Kinetic Energy? • The energy an object has because of its motion • It depends on 2 things: • Mass • Velocity • An aircraft carrier moving 30mph has tremendous kinetic energy • A water molecule moving 10mph has little kinetic energy

5. Potential or Kinetic? • A rolling ball • A bow with an arrow ready to fire • A pile of fire wood • A falling avalanche • A tank of gasoline • A student walking to class • A flying bird • A chicken patty

6. Potential energy comes in many forms: • Gravitational Potential Energy • Elastic Potential Energy • Chemical Energy • Nuclear Energy

7. What is gravitational potential energy (GPE)? • Gravitational Potential Energy - energy stored in an object because of its potential to fall and do work as it falls • The heavier the object and the further it can fall, the more potential it has to do work • GPE = weight x height

8. Gravitational Potential (GPE) • GPE is released as an object falls

9. GPE sample problem: • How much GPE does a 100N rock have if it is 20m above the ground? • GPE = weight x height • GPE = 100N x 20m • GPE = 2000 Joules • Remember: all forms of energy are measured in joules

10. Hydroelectric dams use GPE • We build dams to pile water high • The water flows down through the dam with great force, turning generators which produce electricity

11. What is Elastic Potential Energy (EPE)? • Elastic Potential Energy (EPE) -energy stored in an object that is stretched or compressed • EPE can be stored in springs, elastic bands, bouncy balls and bows. • Wind-up toys and old watches use springs that store EPE

12. Elastic Potential Energy (EPE)

13. Elastic Potential (EPE) • EPE is released when the object snaps back to its original shape

14. What is Chemical Energy? • Chemical Energy -energy stored in chemical bonds between atoms • Chemical energy is released when the chemical bonds are broken • EX. The bonds are broken during combustion and digestion

15. What are some sources of chemical energy? • foods • living things • fuels (anything that burns) • batteries

16. What is Nuclear Energy? • Nuclear energy – energy stored in the nucleus of an atom • Nuclear energy is released when a nucleus is split or when nuclei join together and become one new nucleus. • Splitting is called fission • Becoming one is called fusion

17. What are some sources of nuclear energy? • Plutonium in nuclear weapons • Uranium in nuclear power plants • The Sun and all stars

18. Notes 13– Forms of Energy Part 2

19. Kinetic energy comes in many forms: • Mechanical Energy • Heat Energy • Light Energy • Sound Energy • Electricity

20. What is mechanical energy? • Mechanical Energy– motion energy of objects and substances • Moving machine parts that do work have mechanical energy • Moving air and water (wind and waves and currents) have mechanical energy

21. Wind turbines use mechanical energy to produce electricity

22. Moving objects can do work • What two things determine how much work a moving object can do? • Its mass • Its velocity (speed)

23. Calculating mechanical kinetic energy • To calculate the mechanical kinetic energy of an object use the formula below: • Kinetic Energy = ½ mass x velocity2 • KE=½ mv2 • m is mass in kilograms (kg) • v is velocity in meters per second (m/s)

24. Sample Problem A • How much kinetic energy does a 20 kg fox have when it’s moving 2 m/s? • KE=½ mv2 • KE=½ 20kg x (2m/s) 2 • KE=½ 20kg x (2m/s x 2m/s) • KE=10kg x 4m/s • KE=40 joules

25. Sample Problem B • How much kinetic energy does the same 20 kg fox have when it’s moving 4 m/s? • KE=½ mv2 • KE=½ 20kg x (4m/s) 2 • KE=½ 20kg x (4m/s x 4m/s) • KE=10kg x 16m/s • KE=160 joules

26. What is heat energy? • Heat energy – The kinetic energy of the particles within a substance • The hotter something gets the faster its particles are moving

27. How is heat used to do work? • Heat is used to do work in an internal combustion engine. • Spark plugs ignite gasoline inside the engine. • The burning gas expands rapidly pushing on the pistons • The moving pistons generate the force that moves the car forward

28. What is light energy? • Light energy – the motion of waves of electromagnetic energy • Light travels 186,000 miles per second. That’s 7 ½ times around Earth in a second. • It takes 8 minutes and 20 seconds to reach earth from the sun.

30. Light as an energy source • Solar panels can convert light into electricity • The sun warms Earth and provides the energy living things need to do work

31. What is electricity? • Electricity - Motion of electrons through a conductor • Electricity creates a magnetic force that electric motors use to do work.

32. What is sound energy? • Sound energy -Pressure waves moving through a solid, liquid or gas • There is no sound in space because there is no matter

33. Law of Conservation of Energy • Energy cannot be created nor can it be destroyed • The total amount of energy in the universe remains constant • Energy can be transferred - move from place to place • Energy can be transformed - change from one form to another