1. Energy
Chapter 4

2. What is energy? The ability to cause change Moving baseball had energy
Caused the window to change
Need energy to yawn, open a book or write with a pen…

3. Different Forms of Energy
Electrical
Chemical
Radiant
Thermal

4. Kinetic Energy Energy in motion Depends on object’s mass and speed
Measured in joules
Formula KE=1/2(m)(v2)
Unit= Joules (J)

5. Potential Energy Stored energy Potential to cause change
Amount due to position
Types:
Elastic PE- stored by something that can stretch
Chemical PE- stored in chemical bonds
Gravitational PE- stored by anything that can fall
- based on mass and height

6. Transforming Energy Light bulb: electrical to light & thermal energy
Gasoline: electric spark ignites gas molecule producing thermal energy, gases expand and move parts of car = mechanical kinetic energy
Others?

7. Conversions between PE & KE
Mechanical energy is the total amount of KE and PE in a system

8. The Law of Conservation of Energy
Energy cannot be created or destroyed only transferred
Total amount of energy in the universe does not change
Electrical energy =
Thermal energy
Kinetic energy
Sound energy

9. Here comes Mr. Friction again!
Swinging on a swing, you will eventually come to a stop… did the KE just disappear?
No! Some energy transferred back to PE and some was changed to heat by friction… the swing’s chains rub on the hooks and air rushes past the swinger  thermal energy!
Amount of total energy is still the same

10. Mass to Energy Special kind of energy conversions
Nuclear Fusion: combining atoms to transform mass into energy  SUN!!
Nuclear Fission: atomic nuclei are split to transform mass into energy  uranium

11. Torque
a measure of how much a force acting on an object causes that object to rotate
object rotates about an axis
T = Force x distance

12. Force
distance