Energy
Chapter 5
What is Work?
Work occurs when a force acts upon an
object in the direction of the force applied
 If you push against a wall and the wall
doesn’t move, have you done any work?
 Unit is the Joule (J)

What is Energy?
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The ability to do work
Unit is the Joule (J)
Energy can be transferred from one object to
another
Reflect

What do you think of when you think of
energy? Draw a picture of what energy
means to you.
Kinetic Energy
Energy of motion
 Kinetic Energy depends on speed and
mass
 Kinetic energy = mv2
2
 m is mass, v is speed (velocity)
 Speed has more of an effect on kinetic
energy than mass does because speed
is squared.

Reflect

Draw a picture of something that has
kinetic energy

Do the math:
A
200 kg car is travelling at a speed of 10
km/hr. What is the kinetic energy of the car?
Show all work
Potential Energy

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Energy of position or
shape
Ex.- the bow is not
moving, but it has
potential energy
because work was
done to change its
shape
Gravitational potential energy
Energy due to an object’s position above
the earth’s surface
 The amount of energy is determined by
the object’s weight and its distance above
the earth’s surface


Gravitational potential energy = weight x height
Reflect

Draw a picture of something that has
gravitational potential energy

Do the math:
A
toy is 40N and is on a shelf that is 10
meters above the floor. What is the
gravitational potential energy of the toy?
Show all work
Mechanical Energy

Total energy of motion and
position of an object

Mechanical energy = potential energy + kinetic
energy
Reflect

Do the math:
A
ball has a potential energy of 5 joules at the
highest point of a bounce and a kinetic energy
of 25 joules while the ball is moving. What is
the total mechanical energy of the ball?
Show all work
All forms of energy can be categorized
as either kinetic or potential

Potential
 Stored
energy
 Energy of position
 Chemical
 Nuclear
 Stored Mechanical
 Sound

Kinetic
 Energy
of motion
 Waves, electrons,
atoms, molecules, and
substances
 Radiant
 Thermal
 Motion
 Sound
 Electrical
Matter

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All matter is made up of particles in motion.
Because the particles are in motion, they have kinetic
energy.
At higher temperatures particles move faster and
therefore have more kinetic energy.
Reflect

Draw pictures of the molecules in ice,
water and steam in the boxes and answer
the questions
Which has the most energy – ice, water, or
stream?
 Which has the least energy – ice, water, or
steam?

Thermal Energy

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The total internal energy of the particles that
make up an object. The vibration and
movement of atoms and molecules within the
substance.
The faster the particles move, the more
thermal energy they have
The bigger the object is, the more thermal
energy it has because there are more
molecules that move
Geothermal energy is an example of thermal
energy
Reflect
Name 3 things that have a little bit of
thermal energy
 Name 3 things that have a lot of thermal
energy
 Which has more thermal energy – the
ocean or a lit match?

Chemical Energy

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Energy of a compound that changes as the
atoms are rearranged
Form of potential energy
The more atoms that are bonded together in a
compound, the more potential energy that
compound has
Energy stored in the bonds of atoms:
 Biomass,
petroleum, natural gas, propane and coal
are examples
 Food also has chemical energy
Photosynthesis uses light energy to make
sugars
 Plants absorb the light in their leaves and
change it to chemical energy
 When we eat, we absorb the chemical
energy

Reflect

Circle where you would find chemical
energy
H
H
O
Cl
Cl
Electrical Energy
The energy of moving electrons
 Lightning and electricity
 Electricity is by the changing position of
magnets so it can be considered a form of
potential energy
 When you plug something in electrons
move back and forth transferring energy
so it is a form of kinetic energy
 Electrical energy is produced at power
plants and then transferred to your home

Source:
http://www.eia.doe.gov/kids/energyfacts/sources/electricity.html
#HowIsATransformerUsed?
Reflect

List 5 things you use daily that use
electricity
Sound Energy
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Caused by an object’s vibrations
Sound is the movement of energy through
substances in longitudinal waves
Is both potential and kinetic
To make an object vibrate, work must be done
You change the shape therefore you create
potential energy
When released, air particles are moved creating
kinetic energy
Sound waves cause air
to vibrate which
transmit
energy
Reflect

Write a short song about sound energy to
the tune of Mary Had a Little Lamb
Light (Radiant) Energy

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Radiant energy is electromagnetic energy that
travels in transverse waves
Light energy is an example of radiant energy
Light energy is made up of photons which are
little packets of energy
Part of the electromagnetic spectrum
Electromagnetic Waves have
different wavelengths
When you listen to the
radio, watch TV, or cook
dinner in a microwave
oven, you are using
electromagnetic waves.
Source:
http://imagers.gsfc.nasa.gov/ems/waves3.
html

Radio waves, television
waves, and microwaves are
all types of electromagnetic
waves. They only differ from
each other in wavelength.
Wavelength is the distance
between one wave crest to
the next.

Waves in the electromagnetic spectrum vary in
size from very long radio waves the size of
buildings, to very short gamma-rays smaller than
the size of the nucleus of an atom.
Reflect

Put the following in order of wavelength
starting with the shortest and ending with
the longest: Infrared; TV; X-rays; AM
Radio; Visible light; Microwave
Nuclear Energy
The energy within the nucleus of an atom
 Two types:

– this is done by the sun. It is when
the nuclei of atoms are fused together thereby
releasing a huge amount of energy
 Fission – this is done by nuclear power plants.
It is when the nuclei of an atom is broken
apart thereby releasing a huge amount of
energy
 Fusion
Reflect
Is this Fusion or Fission?
Is this Fusion or Fission?

List two good things about nuclear energy

List two bad things about nuclear energy