1. Energy: The Ability to do Work

2. Work: transfer of energy by a force.
Energy is transferred by a force applied over a distance. The climbers are transferring chemical energy into gravitational potential energy. We would say the work they do inclimbing = their gravitational potential energy at the top + thermal energy produced.
Work is the name for the transfer of energy. When money is transferred we might call it "spending" or "deposit" but the transfer of energy is done by work. If force is a function of position, work is the integral of F "dot" dx. For a constant force this boils down to W = F x cos theta.

3. Kinetic Energy KE = ½ mv2
Energy of motion - moving mass can do work.

4. Gravitational Potential Energy Ug = mgh
Energy of mass lifted in a gravitational field. Mass at this height will be pulled down by gravity and will do work.

5. Elastic Potential Energy Ue = ½ kx2
Energy of stretch. Proportional to k, the stiffness, and the amount of stretch, squared.

6. Electrical Energy
Radiant Energy

7. Thermal Energy: A rise in temperature or change in chemical bonds
Energy transfers are almost always "non-conservative", that is part the of the energy is transformed into thermal energy and is not useful for doing work anymore. Thermal energy can be used to do work, but it is inefficient - impossible to convert all thermal energy into mechanical energy. In physics world the production of thermal energy is ignored.

8. Contest: List several examples of energy in each category.
Kinetic Energy: Energy of motion
Potential Energy: Stored
Radiant Energy: Radiated
Thermal Energy: (Actually a type of kinetic energy)

9. Unit for Work, Heat, and Energy: Joule
1 Cal Diet Coke = 4000 Joules
1 Joule = 1 Newton meter
1 Newton = 1 kg m/s2

10. 1 BTU = 1054Joules
1 gallon gas = 125,000 BTU

11. Eureka Movies (10 minutes):
Work (8)
Kinetic Energy (9)

12. Heat: transfer of thermal energy by radiation, convection, conduction.

13. Electricity is Kinetic Energy!
Where does our electricity come from?

14. Transformed and Transferred Energy
Radiant
Nuclear
Kinetic
Chemical
Chemical
Thermal

15. Nuclear, coal, geothermal, natural gas – most of our energy “turns the crank”.

16. These turn the crank.

17. Solar Panels convert directly to electricity.

18. No energy converter is 100% efficient:
Solar Panels: 4% efficiency in 1980
12% efficiency today
42% in lab
Wind Energy: Theoretical max 57%
Actual 30%?
Conventional: 35-45% efficiency

19. Today Tomorrow Then… Conservation of Energy
Finish Activity (Parts 2 and 3)
Tomorrow
Practice Conservation of Energy
Then…
Work
Power

20. Conservation of Energy
Within a system energy cannot be created or destroyed, only converted from one form to another.
KEInitial + PEInitial = KEFinal + PEFinal

21. Conservation of Energy
For our problems, we will ignore dissipated energy unless the problem says not to. (100% conversion)
If the PE is GPE this is the equation…
½ mv2 + mgh = ½ mv2 + mgh

22. Problem #1
A 2 kg ball is at rest at the top of a 2 m tall ramp. It rolls to the bottom of the ramp. What is its velocity at the bottom of the ramp?
½ mv2 + mgh = ½ mv2 + mgh