1. Chapter Energy

2. Section 1: The Nature of Energy
What is Energy—
Energy is present all around us all day
Energy changes are taking place constantly
Ex: baseball flying and hitting a window, combing your hair, walking to class, etc

3. Energy is the ability to cause change
Anything that causes change must have energy
There are many different forms of energy including electrical, chemical and thermal

4. Kinetic Energy -is energy in the form of motion
Ex: spinning wheel, sprinting runner, football passing through goalposts
Amounts of Kinetic Energy depend on two quantities: mass and velocity
(more mass = more energy)
(more velocity = more energy)

5. Calculating Kinetic Energy
The equation for calculating kinetic energy is:
Kinetic energy = ½ mass X velocity^2
Joule—the SI unit of energy

6. Potential energy -is stored energy due to position
Objects that have potential energy have the ability to cause change
Elastic Potential Energy= energy stored by something that can stretch or compress (ex: rubber band)
Chemical Potential Energy = energy stored in chemical bonds (ex: atoms)

7. Gravitational Potential Energy (GPE)
Gravitational Potential Energy is energy stored by objects that are above Earth’s surface
The amount depends on the MASS of the object, Acceleration Due to Gravity and HEIGHT above the ground
GPE = mass X 9.8 m/s/s X height
(GPE is measured in Joules also)

8. Section 2: Conservation of Energy
Transforming electrical energy
Happens all day, everyday
Ex: lightbulbs transform electrical energy into light
Some of the electrical energy is turned into thermal energy (hot bulbs)
Ex: alarm clock, straighteners, toaster, etc.

9. Transforming chemical energy:
Fuel is stored in the form of chemical potential energy
Ex: Engines transform chemical potential energy stored in gas into kinetic energy
Ex: Green plants convert light energy from the Sun into stored energy in chemical bonds

10. Conversions between kinetic and potential energy
Many situations involve conversions between potential and kinetic energy
Ex: bicycles, roller coasters, swings, etc.
Mechanical energy is the total amount of potential and kinetic energy in a system
Mechanical energy = GPE + KE

11. When energy is transformed from potential to kinetic, the potential energy is not LOST, it has simply been converted, but the total amount of energy remains the same
Ex: Pg. 109—apple tree, baseball, swing

12. Law of Conservation of Energy:
Kinetic and potential energy are constantly changing as the object speeds up and slows down
However, mechanical energy (total energy) stays constant
So: -Energy cannot be created or destroyed, it simply changes form

13. Friction and the Law of Conservation of Energy
Friction slows moving objects, which seems to decrease mechanical energy of an object.
However, friction converts energy to other forms such as thermal energy (heat)

14. Converting Mass into Energy
Nuclear fusion—a special kind of energy conversion
During this process a small amount of mass is transformed into a tremendous amount of energy by fusing atomic nuclei (sun)
Nuclear fission—similar process, but nuclei are broken apart, not fused together

15. Human Body –Energy Conversions
Complex chemical and physical processes in the body obey the law of conservation of energy
Energy is stored as fat and converted to energy as needed for life processes
1 Calorie (C) is equal to 4,184 J
Every gram of fat supplies 9 C of energy
Section 2 Assessment questions