Transcript Energy: Review

What is Energy?
Joke of the Day
 Where do you put dirty lab equipment?
Answer
 The zinc!
Energy – The ability to do work or to
cause a change.
 Kinetic Energy
 The energy of motion. A moving object has the most
kinetic energy at the point where it moves the fastest.
 Potential Energy
 Stored energy; the energy an object has due to its
position, molecular arrangement, or chemical
compostion.
Is it kinetic or potential energy
Example
Blood flowing through the body
A car moving down the street
An apple in a tree
A bug crawling along a sidewalk
A car at a stop sign
An airplane sitting on a runway
A guitar string vibrating
Water in a waterfall
Kinetic
Potential
Is it kinetic or potential energy
Example
Blood flowing through the body
A car moving down the street
Kinetic
X
X
An apple in a tree
A bug crawling along a sidewalk
X
X
A car at a stop sign
X
X
An airplane sitting on a runway
A guitar string vibrating
Water in a waterfall
Potential
X
x
Types of Potential Energy
1. Chemical Energy – Chemical energy is stored
in the bonds of atoms and molecules.
Examples: Biomass, Food, petroleum, natural
gas, propane and coal.
2. Nuclear Energy – the energy stored in the
nucleus of an atom. It is the energy that
holds the nucleus together. Example: The
radioactive decay of the nucleus of a uranium
atom.
Types of Potential Energy (cont.)
3. Gravitational Energy – the energy of place or
position. Example: Water that is held in a reservoir
behind a hydropower dam has gravitational
potential energy.
4. Stored Mechanical (elastic) energy – the energy
stored in objects or substances by the application of
force. Example: Compressed metal springs and
stretched rubber bands.
Types of Kinetic Energy
1. Radiant (light) energy – is
electromagnetic energy that travels in
transverse waves. Examples: Visible light,
x-rays, gamma rays, radio waves, and
solar energy.
2. Thermal (heat) Energy – the internal
energy in substances. It is the vibration
and movement of atoms and molecules
within substances. Example: Geothermal
energy.
Types of Kinetic Energy (cont.)
3. Mechanical (motion) energy – The movement
of objects or substances from one place to
another.
4. Sound Energy – Sound is the movement of
energy (vibrations) through objects or
substances in longitudinal waves.
5. Electrical Energy – the movement of electrons.
Example: Lightning and electricity
Identify the type and form of energy
Example
Form (s)
Type (s)
(Kinetic or
potential)
A running dog
A burning candle
A book on a table
A green plant
Sunlight
A battery
A cup of coffee
Thermal , Mechanical, Chemical
KE
Identify the type and form of energy
Example
Form (s)
Type (s)
A running dog
Mechanical,
Thermal,
Chemical
KE, PE
A burning candle
Thermal,
Chemical, Light
KE, PE
A book on a table
Gravitational
PE
A green plant
Chemical
PE, KE
Sunlight
Radiant, Light,
Thermal
KE
A battery
Chemical,
electrical
PE, KE
A cup of coffee
Thermal, chemical
KE, PE
Both
Moving Energy
Kinetic Energy
increases as mass
increases
The amount of
Kinetic energy is
determined by mass
and velocity.
Both have
the ability to
cause
change.
Thermal
Mechanical
Electricity
Radiant/Light
Sound
Kinetic Energy
Stored Energy
due to an object’s
position and
Chemical
composition
Nuclear
Chemical
Elastic (Stored
Mechanical)
Gravitational
Potential Energy
Class Notes:Calculating Energy
 To calculate the kinetic energy of a
moving object you must know the mass
and velocity. To calculate you use the
following formula:
Kinetic energy (KE) = 1 mass x velocity2
2
What is the kinetic energy of a
5 kg object moving at 7 m/s?




KE = ½ (mass) x (velocity)2
KE = ½ (5 kg) x (7 m/s)2
KE = 2.5kg x 49 m2/s2
KE = 122.5 kg●m2 is equal to Joules
s2
 KE = 122.5 Joules
What is the kinetic energy of a
10 kg object moving at 8 m/s?




KE = ½ (mass) x (velocity)2
KE = ½ (10 kg) x (8m/s)2
KE = 5kg x 64 m2/s2
KE = 320 kg●m2
s2
 KE = 320 Joules
Calculating Potential Energy
 To calculate the potential energy of an object you must
know the mass, height, and gravitational velocity
(g = 9.8m/s2). To calculate you use the following
formula:
GPE = mgh
Gravitational Potential Energy = mass x gravitational velocity x height
What is the gravitational potential energy of a diver
with a mass of 60 kg who is 10 m above the water?
 GPE = mass x gravitational velocity x height
 GPE = 60 kg x 9.8 m/s2 x 10 m
 GPE = 60 kg x 98 m2/s2
 GPE = 5,880 Joules
What is the gravitational potential energy of a rock
with a mass of 20 kg who is 5 m above the ground?




GPE = mass x gravitational velocity x height
GPE = 20 kg x 9.8 m/s2 x 5 m
GPE = 20 kg x 49 m2/s2
GPE = 980 Joules
Energy Transformations
 Energy can be transformed from one form to another.
 Devices such as light bulbs, hair dryers, and automobile engines
convert one form of energy into other forms.
Mechanical energy = Kinetic Energy + Potential Energy
How many examples of energy transformations can
you fill in the chart below?
Chemical
Electric
Chemical
Battery
Electric
Television
Heat
Light
Sound
Car
Running
Stove
Heat
Fire
Light
Sun,
Lava,
Tread Mill
Radio
Stop Light
Mechanical
Sound
Mechanic
al
Running
Microwave
Echo
The Law of Conservation of Energy
 According to the law of conservation of energy,
energy cannot be created or destroyed (it can only be
transformed from one form to another).
 Friction converts mechanical energy into thermal
energy.
 Fission and fusion are nuclear reactions that convert a
small amount of mass in a nucleus to an enormous
amount of energy
How are work and energy
created?
 When work is done, energy is transferred.
Classwork
 Complete NTG section 13.1 and 13.2