Energy

1
Energy

• Energy is the ability to do work
• Energy is typically not seen
• We observe energy in action as it is converted
  from one form to another

2
Types of Energy

• Mechanical
• Motion of objects
• Heat
• Heat is actually a measure of how much the atoms
  are moving in an object
• Electromagnetic
• Light radio waves
• Sound
• Vibration of molecules in a pattern created by a
  source

3
Types of Energy

• Electrical
• Moving electrons
• Magnetic
• Attraction repulsion of north and south poles
• Chemical
• Based on chemical reactions
• Nuclear
• Nuclear energy is created by two methods
• Fusion the joining of atoms to create a new
  atom
• Fission the splitting of an atom into parts

4
2 Varieties of Most Types of Energy

• Energy will come in one of two types
• Potential stored energy
• Kinetic energy in motion

5
Law of Conservation of Energy

• Energy can neither be created nor destroyed
• It can change form
• Sound becomes mechanical in your ear
• Chemical becomes electrical in a battery
• Chemical becomes mechanical in your car engine

6
Work

• When energy is used to do something, work is
  accomplished
• Work Force X Distance
• W FxD
• Work is measured in Joules (J)

7

• I lift a 2 kg book 2 meters into the air
• I have done 40 J of work
• As the book is held in the air at 2 meters, it
  has 40 J of potential energy
• If I drop the book, it will do 40 J of work on
  the way to the floor

8
You try it . . .

• How much work is done in when an elevator lifts a
  70 kg person 20 m into the air?
• Wfd, fma
• F (70 kg)(9.8 m/s2)
• F686 N
• W(686 N)(20 m)
• W13720 J

9
How much PE?

• If the 70 kg person is now 20 m up, how much PE?
• PE mgh
• PE (70 kg)(9.8 m/s2)(20 m)
• PE 13720 J

10
Machines Transform Energy

• Because energy is not created or destroyed
• work input work output
• Sometimes some of the input is converted to sound
  or heat due to friction

11
Simple Machines
12
What is a machine

• A machine is something that changes the magnitude
  (amount) or direction of a force
• It does not make for less work, only makes the
  work easier!!

13
6 Simple Machines

• Incline Plane
• Wedge
• Screw
• Lever
• Pulley
• Wheel Axle

14
Incline Plane

• This is a ramp
• The slower the slope, the less force needed
• The slower the slope, the more distance needed

15
Wedge

• This is two incline planes put together
• An axe, a knife, and the cutting part of scissors
  are all wedges
• A wedge will separate material as it pushes
  through

16
Screw

• A screw is an incline plane that is wrapped
  around a cylinder
• Screws, bolts, and spiral staircases are all
  examples

17
Lever

• A lever has two parts
• The lever (the part that moves)
• The fulcrum (the part or location that the lever
  moves around

18
Classes of Levers

• Three classes of levers
• 1st class a seesaw
• 2nd class a wheelbarrow
• 3rd class a tennis racket

19
Pulley

• A single pulley will change the direction of the
  force
• Pulleys may be fixed or moveable
• A set of pulleys working together is know as
  block and tackle

20
Wheel Axle

• As the wheel is turned by the effort, the axle
  will turn with more force
• A winch and a rear bike tire are examples of
  wheel and axle

21
Mechanical Advantage

• Mechanical Advantage (MA) is a measure of how
  much the force is multiplied