Download Energy

Energy
Table of Contents
What Is Energy?
Book M – 5.1 Pg. 146-150
Forms of Energy
Book M – 5.2 Pg. 151-155
Energy Transformations and Conservation
Book M – 5.3 Pg. 158-163
Energy and Fossil Fuels
Energy - What Is Energy?
Energy, Work, and Power
•The ability to do work or cause change is
called energy.
•When an object or living thing does work on
another object, some of its energy is
transferred to that object.
•You can think of work then, as the transfer of
energy.
•Power is the rate at which energy is
transferred, or the amount of energy
transferred in a unit of time.
Energy - What Is Energy?
Power
Practice Problem
Find the power of a machine that transfers 450 J of energy
in 9 seconds.
Power = 450 Joules / 9 seconds
Power = 50 J/s or watts
Energy - What Is Energy?
Energy
• The two basic kinds of energy are
kinetic energy and potential energy.
• The energy an object has due to its
motion is called kinetic energy.
• Objects that are moving do work,
and therefore have energy.
• Stored energy that results from the
position or shape of an object is called
potential energy.
• This energy has the “potential” to
do work.
Energy - What Is Energy?
Kinetic Energy
• Kinetic energy increases as mass and velocity increases.
• Relationship between kinetic energy, mass, and velocity.
Energy - What Is Energy?
Exponents
An exponent tells how many times a number is used as a
factor. For example, 3 X 3 can be written as 32. You read
this number as “three squared.” An exponent of 2 indicates
that the number 3 is used as a factor two times. To find the
value of a squared number, multiply the number by itself.
32 = 3 X 3 = 9
Practice Problem
What is the value of the number 82?
64
Energy - What Is Energy?
Kinetic Energy
Practice Problem
A 1,350 kg car travels at 12 m/s. What is its kinetic energy?
Kinetic Energy = (1/2) x (1350 kg) x (12 m/s)²
Kinetic Energy = 97,200 Joules
Energy - What Is Energy?
Gravitational Potential Energy
• Potential Energy related to an object’s height is called
gravitational potential energy.
• Gravitational potential energy increases as weight and
height increase.
Energy - What Is Energy?
Potential Energy
Practice Problem
A 380-N girl walks down a flight of stairs so that she is 2.5 m
below her starting level. What is the change in the girl’s
gravitational potential energy?
GPE = (380 N) x (2.5 m)
GPE = 950 J
Her potential energy decreased by 950 Joules.
Energy - What Is Energy?
Elastic Potential Energy
• The potential energy associated with objects that can be
stretched or compressed is called elastic potential energy.
Energy - What Is Energy?
Links on Energy
Click the SciLinks button for links on energy.
Energy - Forms of Energy
Mechanical Energy
•The form of energy associated with the position and
motion of an object is called mechanical energy.
•You can find an object’s mechanical energy by adding the
objects kinetic energy and potential energy.
Energy - What Is Energy?
Mechanical Energy
Practice Problem
If the kinetic energy of a falling apple is 5.2 J and its
potential energy is 3.5 J, what is its mechanical
energy?
Mechanical Energy = Potential Energy + Kinetic Energy
Mechanical Energy = 3.5 J + 5.2 J
Mechanical Energy = 8.7 J
Energy - Forms of Energy
Calculating Mechanical Energy
The kinetic energy of a 500-N
diver during a dive from a 10-m
platform was measured. These
data are shown in the graph.
Energy - Forms of Energy
Calculating Mechanical Energy
Reading Graphs:
According to the graph, how
much kinetic energy does the
diver have at 8 m?
About 1000 J
Energy - Forms of Energy
Calculating Mechanical Energy
Calculating:
Using the graph, find the
kinetic energy of the diver at 6
m. Then calculate the diver’s
potential energy at that point.
Kinetic energy = about 2000
J; potential energy = about
3000 J
Energy - Forms of Energy
Calculating Mechanical Energy
Inferring:
The mechanical energy of the
diver is the same at every
height. What is the
mechanical energy of the
diver?
About 5000 J
Energy - Forms of Energy
Other Forms of Energy
•Most forms of energy, other than kinetic and potential, are
associated with tiny particles that make up the objects.
They include:
• Thermal Energy – the total potential and kinetic energy
of the particles in an object.
• Electrical Energy – the energy of electric charges.
• Chemical Energy – potential energy stored in the
chemical bonds that hold the chemical compounds
together.
• Nuclear Energy – potential energy stored in the
nucleus of an atom.
• Electromagnetic Energy – the energy of light and
other forms of radiation.
Energy - Forms of Energy
Links on Forms of Energy
Click the SciLinks button for links on forms of energy.
Energy - Energy Transformations and Conservation
Energy Transformations
• Most forms of energy can be transformed into other forms.
• A change from one form of energy to another is called
energy transformation.
• There can be single or multiple transformations of energy.
Energy - Energy Transformations and Conservation
Transformations Between
Potential and Kinetic Energy
• One of the most common energy transformations is the
transformation between potential energy and kinetic energy.
• Examples: Waterfalls, Juggling, Pendulum, and Pole Vault
Energy - Energy Transformations and Conservation
Transformations Between
Potential and Kinetic Energy
A pendulum continuously transforms energy from kinetic to
potential energy and back.
Energy - Energy Transformations and Conservation
Energy Transformations Activity
Click the Active Art button to open a browser window and
access Active Art about energy transformations.
Energy - Energy Transformations and Conservation
Conservation of Energy
• The law of Conservation of Energy states when one form of
energy is transformed to another, no energy is destroyed in the
process.
• Energy can not be created or destroyed.
• Whenever a moving object experiences friction, some of its
kinetic energy is transformed to thermal energy this shows that
energy is not destroyed, just transformed.
• Einstein discovered that matter can be transformed to energy.
• Destroying a small amount of matter can release huge
amounts of energy, so the law of conservation had to be
adjusted to state that matter and energy together are always
conserved.
Energy
Graphic Organizer
Energy
exists as
Potential
energy
Kinetic
energy
measured in
is the ability
to do
Joules
Work
can be
Elastic
Gravitational
which at a
given rate is
Power