1. Energy
8th Grade
Mrs. Boguslaw

2. What is energy? Energy = the ability to do work
When one object does work on another, energy is transferred from one object to the other
Measured in Joules (J) …like what other thing we just studied?

3. Kinetic Energy Kinetic Energy = the energy of motion
All moving objects have kinetic energy
KE =
mv2 2

4. Calculating Kinetic Energy
mv2
KE =
What is the kinetic energy of a car that has a mass of 1200 kg and is moving at 20 m/s? 2

5. Kinetic Energy
KE =
At the same speed, which will have more kinetic energy, a small car or a large bus? Why?
mv2 2

6. Kinetic Energy
KE =
Which do you think would have more of an effect on kinetic energy - changing the mass or changing the speed? Why?
mv2 2

7. Potential Energy
Potential Energy = the energy that an object has because of the position, shape, or condition of the object
A stretched bow has potential energy stored in the string
A book on a shelf has potential energy because of gravity

8. Gravitational Potential Energy
GPE = weight x height
When you lift something, you use a force that is against gravity and transfer energy to the object
Depends on where your “ground” is - based on point of view!

9. Mechanical Energy
Mechanical Energy = the amount of work an object can do because of potential and kinetic energy
the total energy of both the motion and position of an object

10. Mechanical Energy
Mechanical Energy = potential energy + kinetic energy
ME = PE + KE

11. Thermal Energy
Thermal energy = all of the kinetic energy due to the random motion of the particles that make up an object
The warmer an object is, the faster the particles move —> more thermal energy!

12. Chemical Energy
Chemical energy = energy that changes as atoms are rearranged
A form of potential energy - depends on the arrangement and position of atoms in a compound
Example: digesting food

13. Electrical Energy Electrical energy = the energy of moving electrons
Until you plug in an electric device, it is potential energy

14. Sound Energy Sound energy = vibrations in the air transmit energy
Example: in a guitar string, energy is stored as potential energy as you stretch it. When you let it go, potential energy is turned into kinetic energy that vibrates the string, which vibrates air particles and makes sound

15. Light Energy
Light energy = the vibrations of electrically charged particles
Light energy does not have to be carried through matter - it can move through a vacuum!

16. Nuclear Energy
Nuclear energy = energy that comes from changes in the nucleus of an atom
Atoms have a lot of potential energy because of the position of particles in the nucleus of an atom
When two nuclei join together or one splits apart, lots of energy is released
The energy of the sun is nuclear energy

17. Energy Conversions Ch. 5, Sec. 2

18. energy conversion a change from one form of energy to another
any form of energy can change into any other form of energy

19. Highest PE
Least KE
Highest KE
Least PE

20. elastic potential energy
you can stretch a rubber band and store energy in it
when the rubber band is let go, the potential energy is converted to kinetic energy

21. how does a light bulb convert energy? electrical energy —>
light energy AND…
heat energy

22. how does a battery convert energy?
chemical energy —>
electrical energy

23. alarm clock how does a digital alarm clock convert energy?
electrical energy —>
sound energy AND light energy

24. how does a blender convert energy? electrical energy —>
sound energy AND…
kinetic energy

25. blowdryer how does a blowdryer convert energy? electrical energy —>
kinetic energy in the motor AND…
heat energy AND…
sound energy