1. The Nature of Energy

2. Energy Every change that occurs involves ENERGY
Moving objects have energy
You can tell an object has energy when it:
Changes its environment
Changes itself
Energy
Electrical – moving electrons
Chemical – from bonds
Thermal- heat

3. Energy Energy exists in many different forms
It may look different, but it’s still energy.
Examples: fire, movement, gasoline in a bucket

4. Energy Types Kinetic energy- energy in the form of motion
Depends on mass and velocity of an object
Increase in either mass or velocity = increase in energy
KE =1/2 mv2
Units = kg*m2/s2
KE = ½ mv2 Velocity changes will impact KE more because velocity is squared.

5. Types of Energy Potential Energy – energy of position
Energy in stationary objects and bonds
Elastic Potential Energy – Energy of compression or stretching
Chemical Potential Energy – Energy stored in bonds
Gasoline, food, hand warmers

6. Types of Energy
Gravitational Potential Energy- Energy stored due to position above the surface of Earth
Depends on mass of object, height of object above ground, and acceleration due to gravity
GPE = m x h x a
All energy – measured in units of Joules
1 J = 1 kgm2/ s2
Energy can be converted:
As an object falls, GPE decreases and KE increases

7. Law of Conservation of Energy
Energy cannot be created or destroyed.
E is constant in universe
Can only be transformed from one type to another
Energy can be transformed into non-useful forms, like heat
“Disappearing energy” – doesn’t disappear
Is converted into thermal energy by friction

8. Demo #2 Question #1: Where is the energy come from?
Question #2: How does this demonstration illustrate the Law of Conservation of Energy?
Question #3: At what point in the pendulum's swing is its gravitational potential energy highest?
Question #4: Describe the point at which the kinetic energy of the pendulum is highest.

9. Changing Forms of Energy
Many devices convert energy from one form to another
Electrical to thermal
Mechanical to Electrical
In Vehicles:
Engine: Chemical Energy to Kinetic energy
Spark plug: Electrical Energy converts gasoline’s chemical energy to thermal energy
Thermal Energy causes gases to expand
Expanding is mechanical energy, which moves parts of the car = kinetic energy

10. Conversions Between Forms of Energy
Plants: light into chemical
Uses E from sunlight to make bonds
Mechanical energy – total KE and PE in a system
ME = KE + PEG + PEe
Amount of ME is due to:
Position and Motion
Can PE be converted into KE?

12. Pra

14. Practice problems for kinetic and potential energy
What is the kinetic energy of a car with a mass of 500 kg and a speed of 5 m/s?
What is the GPE of a person standing at the top of a ladder with a height of 15 meters? The person has a mass of 80 kg.

15. Practice continued…
What is the kinetic energy of a child on a swing with a mass of 30 kg and a speed of 3 m/s?
What is the GPE of a bowling ball with a mass of 1.5 kg and held 2 meters above the ground?

16. Resources Roller coaster Animation: