1. Energy

2. ENERGY The ability to cause CHANGE
Anything that causes change must have ENERGY!!
You use energy to function
Different Forms of Energy
Electrical
Chemical
Thermal
Electromagnet
Nuclear
These are like different forms of money

3. KINETIC ENERGY (KE) -The energy of MOTION
-All moving objects have Kinetic Energy!
-Depends on: MASS and SPEED of the object
-Equation:
Kinetic Energy (KE) Joules = 1/2mass(kg) X speed2
KE = 1/2mv2
-Joule (J) = SI unit for Energy

4. Example Problem with Kinetic Energy
-A jogger whose mass is 60kg is moving at a speed of 3 m/s. What is the jogger’s Kinetic Energy?
Mass = 60kg
Velocity = 3 m/s
KE = ??J
KE = 1/2mv2
KE = 1/2(60kg)(3m/s)2
KE = 270 J

5. POTENTIAL ENERGY (PE) -The energy of REST
-Objects at REST have POTENTIAL ENERGY
-Potential Energy is CHANGED into KINETIC ENERGY when MOTION occurs

6. TYPES OF POTENTIAL ENERGY
Elastic Potential Energy = Energy stored by something that can be STRETCHED or COMPRESSED
Ex: Rubber band
2. Chemical Potential Energy = Energy stored in CHEMICAL BONDS
Ex: Food, Natural gas
3. Electrical Potential Energy = Energy stored due to ELECTRICAL CHARGES
4. Nuclear Potential Energy = Energy stored in the NUCLEI OF ATOMS

7. TYPES OF POTENTIAL ENERGY
5. Gravitational Potential Energy: Energy stored by objects due to their POSTION ABOVE EARTH
-Ex: Anything with the potential to FALL
-Depends on: MASS and HEIGHT above ground
-Equation:
GPE (J) = Mass (kg) X gravity (m/s2) X height (m)
GPE = mgh
Remember: Gravity on Earth = 9.8 m/s2

8. GPE Example Problem
-What is the GPE of a ceiling fan that has a mass of 7kg and is 4m above the ground?
GPE = mgh
Gravity = 9.8 m/s2
Mass = 7 kg
Height = 4 m
GPE = (7kg)(9.8m/s2)(4m)
= 274 kgm2/s2 = 274 J

9. To INCREASE GPE 1: INCREASE object’s HEIGHT 2. INCREASE object’s MASS
2KG
2KG
7KG
2KG

10. The Change of GPE to KE -As objects fall, GPE is changed into KE
-KE is LARGEST right before the object hits the ground, thus GPE is the SMALLEST right before hitting the ground
-Objects with MORE GPE move FASTER because they have more KE

11. Converting between KE and PE
-MECHANICAL ENERGY = Total amount of POTENTIAL and KINETIC energy in a system
Mechanical energy = PE + KE
What happens to the mechanical energy as PE and KE are converted into each other?
ME stays the same!! As PE and KE are converted, the FORM of energy changes, but the TOTAL AMOUNT STAYS THE SAME

12. The Law of Conservation of Energy
-States that: ENERGY CAN’T BE CREATED OR DESTROYED!!
-So does this mean the total amount of energy in the Universe is the same at all times???
Friction and Air Resistance
These forces can cause some mechanical energy to change into THERMAL ENERGY!!

13. -SI UNIT: Kelvin (K) or Celsius (0C)
TEMPERATURE
-TEMPERATURE = Measure of the AVERAGE KINETIC ENERGY of the particles in an object
-As temp. INCREASES = Average SPEED of particles INCREASE = KE INCREASES
-SI UNIT: Kelvin (K) or Celsius (0C)

14. THERMAL ENERGY
Sum of the KINETIC and POTENTIAL energy of all the particles in an object

15. THERMAL ENERGY & TEMPERATURE
-As KE INCREASES = TEMPERATURE INCREASES
THUS
-As TEMP INCREASES = THERMAL ENERGY INCREASES

16. THERMAL ENERGY & MASS -As MASS INCREASES = total KE INCREASES THUS
-AS MASS INCREASES = THERMAL ENERGY INCREASES

17. HEAT
-Thermal energy that FLOWS from something at a HIGHER TEMP to something at a LOWER TEMP
-Form of ENERGY
-Measured in JOULES (J)
***Always flows from warmer to cooler***

18. SPECIFIC HEAT
-Amount of HEAT needed to RAISE THE TEMP of 1kg of a material by 10C
-Measured in: J/(kg 0C)
-As a substance absorbs HEAT, its TEMP change depends on the composition of the substance. This is called the Specific Heat of the substance!
Ocean water v/s Beach Sand
(see next slide)

19. TRANSFERRING THERMAL ENERGY
-3 Ways to transfer thermal energy from place to place
1. CONDUCTION
2. CONVECTION
3. RADIATION

20. **HEAT is transferred by COLLISIONS, not by movement of matter**
CONDUCTION
-The transfer of energy by COLLISIONS or TOUCH
-This happens because particles are in CONSTANT MOTION
-Thermal Energy is transferred by collisions between molecules with more KE to molecules with less KE
**HEAT is transferred by COLLISIONS, not by movement of matter**

21. HEAT CONDUCTORS
1. Heat moves faster by conduction in SOLIDS and LIQUIDS than in gases
WHY??
2. The BEST conductors = METALS
Gases are more spread out/collisions are less frequent
All the e – aren’t bonded to atoms, so they move more freely

22. CONVECTION
-The transfer of thermal energy in a FLUID (gas or liquid) by movement of WARMER and COOLER fluid from place to place
-Uses CONVECTION CURRENTS to transfer the energy from WARM TO COOL
-Still uses collisions to transfer as well
-As a fluid increases its temp = it EXPANDS and its DENSITY DECREASES
WHY??
-Particles have more KE = move faster = spread out

23. -Energy = RADIENT ENERGY
RADIATION
-The transfer of energy by ELECTROMAGNETIC WAVES
-Waves can travel through space even though there is no matter THUS Radiation is the only form of energy transfer in space
-Energy = RADIENT ENERGY

24. RADIATION
-Radiation can be ABSORBED, REFLECTED, or TRANSMITTED thru an object
-This depends on: MATERIAL OF OBJECT
-LIGH-COLORED = Reflect more
-DARK-COLORED = Absorb more
-Radiation can be TRANSMITTED thru:
SOLIDS
LIQUIDS
GASES

25. INSULATORS -A material in which HEAT FLOWS SLOWLY
-Good Conductors = BAD INSULATORS
-Good Insulators = Wood, plastic, fiberglass, air
-Gases are usually the BEST INSULATORS

26. CONTROLLING HEAT FLOW
-You can use various materials to control heat flow
Ex: Jacket/sweater
-Living organisms have special features to help control the flow of heat
Ex: Fur, Blubber, Scales (reflect), Color