1. What is energy?

2. Chain of energy

3. Newton’s Laws 1.An object in motion will stay in motion (or rest at rest) unless acted on by an outside force. (Inertia) 2.Force = mass x acceleration (Units: Newtons = kg x m/s 2 ) 3.For every action there is an equal and opposite reaction.

4. Work Energy = ability to do work Work = force exerted over a distance W (or “energy”) = F x d 1 Joule = 1 Newton x 1 meter 1 Joule = 1 Newton x 1 meter 4.18 Joule = 1.00 calorie 4.18 Joule = 1.00 calorie

5. Power Rate at which work is done Power = Work / time Watts = Joules / seconds SO… Energy can also be expressed this way: Energy = Power x time Joules = Watts x seconds

6. Consider: What does it mean to give electrical appliances a rating in watts? What is a kilowatt? What is a killowatt-hour? Why do we describe food in terms of calories?

7. Forms of Energy Kinetic energy = Energy of moving objects KE = ½ mass x velocity 2 KE = ½ mv 2 Joules = ½ kg x (m/s) 2 Potential energy = Energy stored due to position or composition PE = mass x acceleration due to gravity x height PE = mgh Joules = kg x m/s 2 x m

8. Consider: How do each of the following represent KE? Heat radiating from a car The sound of my voice Muscles contracting Light traveling to your eye

9. Consider: How do each of the following represent potential energy? A book on the edge of a table A slice of pizza Two magnets near each other An electrical outlet A stretched rubber band

10. What is heat? Kinetic energy caused by atoms moving and colliding Flows from warm body to cold body Not the same as temperature

11. Temperature Scales ° F = (1.8 x ° C) + 32 ° C = (° F – 32) / 1.8 Both use freezing and boiling points of water as standards Kelvin = ° C – 273 0 K = absolute zero

12. Specific Heat Ability of a material to absorb/lose heat Q = mc Δ t Heat gained/lost = mass x specific heat x change in temp If two substances have equal mass and equal change in temp., what does the amount of heat gained depend on?

13. Heat transfer Conduction – transfer due to atoms colliding or vibrating Convection – transfer due to bulk movement of a fluid (gas or liquid) Radiation – transfer due to electromagnetic radiations (uses electrical/magnetic fields instead of matter) file:///Users/johnb/Desktop/lsps07_int_heattransfer/lsps07 _int_heattransfer.html file:///Users/johnb/Desktop/lsps07_int_heattransfer/lsps07 _int_heattransfer.html How can these types of transfer work together?

14. 1 st Law of Thermodynamics: Conservation of Energy Energy cannot be created or destroyed but can be transformed PE = KE mgh = ½ mv 2 How can our examples of PE be converted into KE? Is the reverse also true? Are energy conversions 100% efficient?

15. 2 nd Law of Thermodynamics: Entropy Statements: 1.Heat will not flow spontaneously from a cold to a hot body. 2.You cannot construct an engine that does nothing but convert heat to useful work. 3.Every isolated system becomes more disordered with time. (Entropy) http://www.stolaf.edu/people/giannini/flashanimat/transpor t/diffusion.swf http://www.stolaf.edu/people/giannini/flashanimat/transpor t/diffusion.swf

16. Applications Can any system transfer energy with 100% efficiency? What does this mean in living systems? How do we maintain order in systems (especially living systems)? Where does energy go? Is it truly “lost”?

17. Back to the Sun – Nuclear Fusion High pressure and high temperature force atoms together Mass converted to energy Energy radiates into space How do atoms relate to energy?