1. WORK AND ENERGY
Chapter 24

2. WORK Must involve force and motion
Force and motion must be acting in the same direction
Examples-lifting a box, pushing a chair
Nonexample-holding a backpack

3. WORK Work is equal to force times distance Work = Force x distance
This is expressed in Joules.
Joule = Newtons x meters

8. EFFORT FORCE The force exerted on an object when doing work.
Example: You push a chair. The force you exert on the chair is the effort force.

9. RESISTANCE FORCE The force applied by the object work is done on.
Example: You push a chair. The resistance force is the force of the chair pushing on you.

10. ENERGY

11. Energy
Energy is the ability to cause change.

12. Source of Energy
Almost all of the energy that can be used today can be traced to the sun.

13. LAW OF CONSERVATION OF ENERGY
Energy cannot be created or destroyed, but it can change from one form to another.
The only thing that changes is the form in which energy appears.

14. POTENTIAL ENERGY Stored Energy
Example: Ball sitting on top of a hill (It has the “potential” to be converted to kinetic energy)

15. KINETIC ENERGY Energy of Motion
If an object isn’t moving, it doesn’t have kinetic energy.

16. GRAVITATIONAL POTENTIAL ENERGY
Energy stored as a result of an object’s position above the ground.
The higher the object is above the ground, the more gravitational potential energy it has!

20. Potential and Kinetic

21. Kingda Ka Videos
Promotional Video
First Person Point of View

22. Kingda Ka 0 to 128 miles per hour (206 km/h) in 3.5 seconds
twisting 90 degrees
height of 456 feet (139.5 m).
The train then descends 418 feet (127 m)
The ride lasts 50.6 seconds.

23. ELASTIC POTENTIAL ENERGY
Energy stored as a result of stretching, twisting, or compressing something.

24. Thermal Energy How much heat an object has.
An object that is warmer, has more thermal energy.
A cup of hot chocolate has more thermal energy than a cup of cold water.

25. SOUND ENERGY
Kinetic energy converted into energy that we can hear.
Example: the kinetic energy of our hands hitting is converted into the sound of clapping.

26. Sound Waves Sound is a type of energy that makes waves.
Sound waves can travel through air, solids, and liquids.
Sound waves cause the eardrum to vibrate, which then move 3 tiny bones in your ear.

27. Light Waves
a wavelength that is visible to the human eye.
ROY G. BIV

28. Wavelength
Wavelength is the distance between any two corresponding points on a wave.
A wavelength is usually crest-to-crest or trough-to-trough

29. Crest & Trough The top part of the wave is the crest.
The bottom part of the wave is called the trough.

30. Refraction
Refraction is the bending of a wave when it enters a medium where it's speed is different.

31. States of Matter
Solid
Liquid
Gas
Plasma

32. Changes of State Evaporation—when a liquid turns into a gas.
Condensation—When a gas turns into a liquid.
Freezing—when a liquid turns into a solid.
Melting—when a solid turns into a liquid.
Sublimation—when a solid turns directly into a gas. (Dry Ice)

34. Thermal Energy
Heat Energy

35. Heat
The energy transferred from something of higher temperature to something of lower temperature.

36. How is Energy Flowing? A glass of iced tea on a warm afternoon.
From the air to the tea.

37. Temperature
A measurement of how much thermal energy is in an object.

38. Temperature We typically use 2 scales to tell temperature Fahrenheit
Celsius

39. Temperature
How do we measure temperature?
A thermometer

40. Thermal Equilibrium Two objects in contact have the same temperature.
Energy continues to move into and out of the objects to maintain equilibrium.

41. Examples
If a pot of boiling water and an ice cube are placed in this room, what will eventually happen to both?
Both will eventually reach room temperature! This is THERMAL EQUILIBRIUM.

42. Energy Transfer
Conduction
Convection
Radiation

43. Conduction Transfer of heat between two objects in contact.
Ex. –pan on a hot stove, spoon in a pan of chili

44. Convection
Heat transfer by means of a heat-carrying medium such as a liquid or gas.
Ex. Movement of materials in a lava lamp.

45. Radiation Ex. The sun’s warmth felt on your skin,
Heat transfer across space.
Ex. The sun’s warmth felt on your skin,
-a marshmallow toasting over a fire.

46. Insulators Example: a Thermos or travel mug for coffee.
Insulators conduct heat poorly.
Example: a Thermos or travel mug for coffee.
Insulation between
your wall and the
outside.

47. ENERGY RESOURCES

48. FOSSIL FUELS
Remains of plants or animals that you can burn today to produce thermal energy.
Includes coal, oil, and natural gas.

49. NONRENEWABLE RESOURCES
A resource that may be replaced only over a very long time or may not be replaced.
Coal, oil, and natural gas.

50. Renewable Resources
Natural resources that can be replaced by natural processes in less than 100 years.
Includes solar, water, wind, and plants

51. HYBRID VEHICLES
A vehicle that uses two or more sources to power the vehicle (usually gasoline and electricity or hydrogen) to power the engine.

52. 2843 Miles Per Gallon

55. HYDROELECTRICITY Electricity generated through the use of waterpower.
Uses dams at lakes and rivers.
Clean, but sometimes disrupts ecosystems.

56. SOLAR ENERGY
Uses solar cells to convert light from the sun into electricity.
Very efficient on sunny days.
Solar cells are expensive to make.

57. WIND ENERGY
Wind energy is harnessed by windmills connected to turbines which turn generators to produce electricity.
Clean and renewable, not reliable.

58. GEOTHERMAL ENERGY
Uses heated water, which comes from geothermal vents.
Iceland has many geothermal power plants.

59. BIOMASS Use animal waste to produce methane gas. Burn wood
Use fuels made from soybeans and corn.

60. NUCLEAR ENERGY
Uses radioactive materials to convert atomic energy into electricity.
Fission-splitting atoms to make energy.
Fusion-combining 2 atoms to obtain energy.

61. Water Cycle Evaporation-liquid water changes into water vapor.
Transpiration-water vapor enters the atmosphere from plant leaves.

62. WATER CYCLE
Condensation-The process of changing from a gas to a liquid.
Precipitation-Rain, sleet, snow, or hail which falls to earth from the sky.
Runoff-the flow of water from rain, snow or other precipitation.