1. Energy
Chapter 15

2. Energy and Its Forms
Section 15-1

3. Energy and Work Energy is the ability to do work.
Work is a transfer of energy.
Both work and energy are measured in joules

4. Kinetic Energy The energy of motion
The kinetic energy of any moving object depends on its mass and speed.
KE = ½ mv2

5. Let’s try one…
A 0.10 kilogram bird is flying at a constant speed of 8.0 m/s. What is the birds kinetic energy?
KE = ½ mv2
KE = ½ (0.10 kg)(8.0m/s)2
KE = 3.2 kg·m2/s2= 3.2 Joules

6. Potential Energy The energy stored as a result of position or shape
An object’s gravitational potential energy depends on its mass, its height, and the acceleration due to gravity.
Elastic potential energy is the potential energy of an object that is stretched or compressed.

7. Let’s Calculate Gravitational Potential Energy
A diver is at the top of a 10.0 meter high diving platform has a mass of 50.0 kilograms. Calculate her potential energy.
PE = mgh
PE = 50.0 kg (9.8 m/s2)(10.0 m)
PE = 4900 kg· m2/s2 = 4900 J

8. Forms of Energy
The major forms of energy are mechanical energy, thermal energy, chemical energy, electrical energy, electromagnetic energy, and nuclear energy.

9. Forms of Energy
Mechanical Energy – the energy associated with the motion and position of everyday objects.
Thermal Energy – since atoms are in constant motion, all matter has kinetic energy. The total potential and kinetic energy of all microscopic particles in an object make up its thermal energy.

10. Forms of Energy Chemical Energy – the energy stored in chemical bonds
Electrical Energy – the energy associated with electrical charges

11. Forms of Energy
Electromagnetic Energy – a form of energy that travels through space in the form of waves
Nuclear Energy – the energy stored in atomic nuclei

12. Energy Conversion & Conservation
Section 15-2

13. Energy Conversion Energy can be converted from one form to another.
Energy conversion – the process of changing energy from one form to another

14. Conservation of Energy
The law of the conservation of energy states that energy can not be created or destroyed
When a moving objects stops moving due to friction, its kinetic energy is turned into thermal energy.

15. Energy Conversions
The gravitational potential energy of an object is converted to the kinetic energy of motion as the object falls.
Pendulums & Pole Vaulters

16. Energy & Mass
Einstein’s equation, E=mc2, says that energy and mass are equivalent and can be converted into each other.
Since c is a very big number (3 x 108), this formula shows that a small amount of mass can make a lot of energy!

17. Energy Resources
Section 15-3

18. Nonrenewable Energy Resources
Nonrenewable Energy Resources – energy resources that exist in limited quantities and, once used, cannot be replaced except over the course of millions of years.
This includes fossil fuels (oil, natural gas, coal), and uranium.

19. Renewable Energy Resources
Renewable Energy Resources – energy resources that can be replaced in a relatively short period of time
This includes hydroelectric, solar, geothermal, wind, biomass, and possible in the future, nuclear fusion.

20. Renewable Energy Resources
Hydroelectric energy – energy obtained from flowing water
Solar energy – sunlight that is converted into usable energy
Geothermal energy – thermal energy beneath Earth’s surface

21. Other Renewable Resources
Biomass energy – the chemical energy stored in living things
Hydrogen fuel cell – generates electricity by reacting hydrogen with oxygen

22. Conserving Energy Resources
Energy resources can be conserved by reducing energy needs and by increasing the efficiency of energy use.
Energy conservation – finding ways to use less energy or to use energy more efficiently