Transcript Slide 1

Laws of Motion and Energy
Chapter Six: Energy and
Machines
• 6.1 Energy and Conservation of Energy
• 6.2 Work and Power
• 6.3 Simple Machines
Investigation 6A
Energy Transformations on a
Roller Coaster
• Where does the marble move the fastest
and why?
6.1 Energy
• Energy is a quantity that measures the
ability to cause change in an object or
system.
We get energy from the
changes in food when it
is digested and stored
in the body.
6.1 Energy
• The unit of measurement for energy is the
joule (J).
• One joule is the energy needed to push
with a force of 1 newton over a distance of
1 meter.
6.1 Systems and variables
• A system is a group
of objects and the
factors that affect
these objects.
• In the car and ramp
system color, light
and friction were not
included in the
system.
What factors were
included in the car and
ramp system?
6.1 Systems and variables
• A factor that
affects a
system is
called a
variable.
Can you name these
five variables?
6.1 Systems and variables
• You may change
the system later
to include new
objects, effects,
or variables such
as friction.
6.1 Energy in systems
• Energy is a measure of a system’s
ability to change or create change in
other systems.
• Energy is an important variable in all
systems.
The energy the car
has due to height
can be compared
on a ramp.
6.1 Kinds of energy
•
•
Energy appears in many forms, such as heat,
motion, height, pressure, electricity, and
chemical bonds between atoms.
Energy can transfer from one form to another.
6.1 Law of conservation of energy
•
The idea that energy
converts from one form
into another without a
change in the total
amount is called the
law of conservation
of energy.
A bow and arrow transform energy from the
stretched bow to the motion of the arrow.
6.1 Energy transformation
•
•
The marble and the track are a system.
This system has two major kinds of energy
called potential energy and kinetic energy.
6.1 Energy transformation
•
•
Potential energy is energy due to position.
When you lift the marble off the ground it gets
potential energy because of its height.
6.1 Energy transformation
•
•
As the marble moves down the track, it loses
potential energy.
Potential energy is converted into kinetic
energy, which is the energy of motion.
6.1 Energy transformation
•
The marble slows down as it goes uphill
because kinetic energy is being changed back
into potential energy.
6.1 Energy transformation
•
•
Conservation of energy says the total energy
stays the same as the marble moves up and
down.
The marble has the most kinetic energy when
its speed is greatest.
6.1 Energy in your life
• A joule is a tiny amount of
energy compared to what
you use every day.
• Some units of energy that
are more appropriate for
everyday use are the
kilowatt-hour, food calorie,
and British thermal unit.
6.1 Conserving Energy
• When you “use” energy
by turning on a light, you
are really converting
energy from one form
(electricity) to other forms
(light and heat).
6.1 Conserving Energy
• Electric power plants don’t make electrical energy.
• Energy cannot be created.
• Energy CAN be converted from other forms of
energy such as chemical, solar, or nuclear energy.
6.1 Conserving Energy
• An average electric power
plant puts out 1,000,000
kwh of electrical energy
per hour.
• That means 120 power
plants are burning up
resources each hour just
to run light bulbs!