Energy

1
Chapter 5
2
Energy

• What is Energy?
• Kinetic Energy Energy in the form of motion
• Running, spinning wheels, etc.
• Potential Energy Stored energy

3
Work

• Definition The transfer of energy through
  motion. A force is exerted over a distance.
• Equation W F x d

4
Practice Problem

• A dancer lifts a 400N ballerina overhead a
  distance of 1.4 m. How much work has he done?
• W F x d
• W 400N x 1.4m
• W 560 N ? m
• W 560 J

5
Practice Problem

• A game show contestant won a prize by pushing a
  bowling ball 20m using his nose. The amount of
  work done was 1470J. How much force did the
  person exert on the ball?
• F W / d
• F 1470J / 20m
• F 73.5 N

6
(No Transcript)
7
Conservation of Energy

• Pendulums

8
(No Transcript)
9
(No Transcript)
10
(No Transcript)
11
Mechanical Energy

• The total amount of kinetic and potential energy.

12
Law of Conservation of Energy

• Energy can change form, but it can not be created
  or destroyed.

13
Energy and the Human Body

• Movement
• The movement of your body is the conversion of
  your bodies potential energy into kinetic energy.
• The food you eat is your chemical potential
  energy.
• Calorie The unit used to measure how much energy
  we get from specific foods.

14
(No Transcript)
15
Temperature and Heat

• The measure of the average kinetic energy of the
  particles in a sample of matter.
• The measure of how hot and cold an object is
  compared to a reference point.
• Reference points could be on a temperature scale,
  like the freezing and boiling points of water

16
Thermal Energy

• Thermal energy is the total potential and kinetic
  energy of all the particles in an object.
• Thermal energy depends on the mass, temperature,
  and phase (solid, liquid, or gas) of an object.

17
Heat

• Heat is the transfer of thermal energy from one
  object to another because of a temperature
  difference.
• Heat always flows from hot objects to cold
  objects.

18
Comparing Temperature Scale

• There are three different temperature scales that
  are commonly used.
• Fahrenheit (?F)
• Celsius (?C)
• Kelvin (K)

19
Common Temperatures Common Temperatures Common Temperatures Common Temperatures
Fahrenheit Celsius Kelvin
Water Boils 212 100 373
Human Body 98.6 37 310
Average Room 68 20 293
Water Freezes 32 0 273
20
Measuring Thermal Energy

• Specific Heat The amount of heat needed to raise
  the temperature of one gram of material by one
  degree Celsius.
• The lower the materials specific heat, the more
  its temperature rises when a given amount of
  energy is absorbed by a given mass.

21
(No Transcript)
22
Specific Heat

• Every material that exists has a different
  Specific Heat.

23
Specific Heat Equation

• Q m x c x ?T
• Q Change in Thermal Energy
• M mass
• C Specific Heat
• ?T (final temp initial temp)

24
Practice Problem

• 1. A 45 kg brass sculpture gains 180,480 J of
  thermal energy as its temperature increased from
  28-48 ?C. What is the approximate specific heat
  of brass?
• Q c
• m x ?T

25
Chapter 6
26
Using Thermal Energy

• Conduction The transfer of energy through matter
  by DIRECT contact.
• Convection The transfer of energy by BULK
  MOVEMENT of matter
• Radiation The transfer of energy in the form of
  waves.

27
Conduction
28
Convection
29
Radiation
30
(No Transcript)
31
Thermal Energy Flow

• Conductors Any material that allows heat to move
  easily.
• Insulators Any material that does not allow heat
  to move easily.
• Insulation Ratings
• R-value A scale that compares the insulation
  ability of different materials.

32
Chapter 7

• Machines..

33
MachinesMaking Work Easier by.

• Lifting our cars (jacks)
• Helping us climb (stairs)
• Moving us (wheels and axles)

34
What are Machines?

• A device that makes work easier by changing the
  force.
• They change the size of the force needed, the
  direction of the force or the distance over which
  a force acts.

35
Advantages of Machines

• Can increase the amount of force on an object.
• Lug nut
• Can increase the distance that the force must
  work within
• Pulley
• Can change the direction of the force
• Oar

36
Simple Machines

• Levers A rigid bar that moves around a fixed
  point called a fulcrum.
• When you put force into a lever it will produce a
  different amount of output force.

37
Levers

• First Class Lever The fulcrum is located between
  the input force and the output force.

38
Levers

• Second Class The output force is located between
  the input force and fulcrum.

39
Levers

• Third Class The input force is located between
  the fulcrum and the output force.

40
Simple Machines - Pulley

• Pulleys are simple machines made from a rope that
  fits into the groove of a wheel.
• Types of pulleys
• Fixed
• Movable
• Pulley System

41
Simple Machines Wheel and Axle

• A Wheel and Axle is a simple machine that
  consists of two disks (or cylinders), each one
  with a different radius.

42
Simple Machines Inclined Plane

• An Inclined Plane is a slanted surface that can
  move an object at a different elevation.

43
Simple Machines Screw

• A Screw is an inclined plane wrapped around a
  cylinder.
• Screws with threads that are closer together have
  a greater ideal mechanical advantage.

44
Simple Machines Wedge

• A Wedge is a V-shaped object whose sides are two
  inclined planes sloped towards each other.

45
Using Machines

• A Compound Machine is a combination of two or
  more simple machines that operate together.
• Car, washing machine etc.

46
Power

• Definition Power is the rate of doing work.
• To increase power you whether increase the work
  done in a given time, or do the amount of work in
  less time.
• Equation
• Power work / time
• Remember!!! Work Force x distance

47
Power Practice Problems

• A figure skater lifts his partner, who weighs
  450N, 1.0m in 3.0s. How much power is required?
• Power work / time
• Power (Force x Distance) / time
• Power (450N x 1.0 m) / 3.0 s
• Power 450 J / 3 sec
• Power 150 Joss or 150 W (Watts)

48
Watts

• Watt is the SI unit for power.
• It represents the amount of Joules per second
• For example, a 40 Watt light bulb requires 40J of
  energy for every second that it is lit.

49
Chapter 21 Electricity
50
Static Electricity

• The property that causes subatomic particles such
  as protons and electrons to repel each other.
• There are two types of electrical charge,
  Positive and Negative.
• Positive charges from protons
• Negative charges from electrons.

51
Static Electricity

• Electric Fields
• The effect an electric charge has on other
  charges in the space around it.
• The charge of static electricity can be
  transferred by friction, contact or induction.

52

• Friction Rubbing, build up of charges
• Contact Touching something directly
• Induction Transfer of charge without direct
  contact.

53
Electric Conductors and Insulators

• Conductor A material through which a charge can
  easily flow
• Insulator A material through which a charge can
  not easily flow.

54
Electric Current

• Flowing Electrons Electrons that move or flow
  in one direction produces an electric current.
• Potential Difference The difference in
  electrical energy between two places in an
  electric field.
• Current
• Direct Current (DC) A current where the charge
  only flows in one direction.
• Alternating Current (AC) A flow of electric
  charge that regularly changes its direction.

55
Battery

• Dry cell LEAVE BLANK
• Wet cell LEAVE BLANK

56
Electrical Circuits

• Symbols (page 609)
• Series Has only one path that the electricity
  can flow
• Christmas lights
• Parallel Has two or more paths for the flow to
  travel
• Household circuitry

57
Chapter 22 Magnetism
58
Magnets

• Magnetism The force a magnet exerts on another
  magnet, can attract or repel.
• Magnetic Field Is strongest near a magnets
  poles will either attract or repel another magnet
  that enters the field.

59
Poles / Magnetic domains

• The parts of the magnet that are the strongest
• North and South
• Opposites attract