Transcript Energy - Cloudfront.net

Chapter 4
Energy
Energy
A. What is Energy?
Energy is the ability to cause change.
1. Different Types of Energy
a. thermal energy
b. chemical energy
c. radiant energy
d.electrical energy
Energy
B. Kinetic energy (KE)- Energy in the form of
motion
a. The amount of kinetic energy an object has
depends on its mass and its velocity
b. KE= ½ mass X velocity2
c. Joule - The SI Unit to measure energy
C. Potential energy (PE)- Energy stored by
motionless things, giving it the potential to
cause change
Energy
3. Elastic potential energy (EPE)- Energy stored by
things that stretch or compress
4. Chemical potential energy (CPE) - Energy stored
in chemical bonds between atoms
5. Gravitational potential energy (GPE) - Energy
stored by things that are above Earth
a. The amount of GPE an object has depends on
its mass, the acceleration due to gravity, and its
height above the ground
b. GPE = mass in kg x 9.8 m/s2 x height in m
Discussion Questions
(Write answers in your notes)
1. Name the different types of energy.
2. How is elastic potential energy different
from chemical potential energy?
Answers
1. Thermal energy, chemical energy,
radiant energy, electrical energy
2. Elastic potential energy is energy stored
by things that stretch or compress.
Chemical potential energy is energy
stored in chemical bonds.
Conservation of
Energy
Changing Forms of Energy
A. Transforming Electrical Energy
1. What device transforms electrical
energy into light and thermal energy?
B. Transforming Chemical Energy
1. Spark plug firing initiates the conversion
of chemical potential energy into thermal
energy
Energy Conversion
A. Energy conversion - energy changing from
one form to another
1. Mechanical energy (ME) - the total amount
of potential and kinetic energy in a system
mechanical energy = kinetic energy + potential energy
Law of Conservation of
Energy
B. Law of Conservation of Energy - Energy may
change from one form to another, but the total
amount of energy never changes
EXAMPLE
1. As a swing moves back and forth, it’s energy
continually converts from kinetic to potential and back to
kinetic
2. Friction Converts some of the mechanical energy into
thermal energy
3. Where is PE the greatest?
A
C
4. Where is KE the greatest?
B
Nuclear Reactions
C. Mass is converted into energy in the
process of fusion and fission
1. Nuclear fusion - Two nuclei are fused
together. Takes place in the sun
2. Nuclear fission - Two nuclei are broken
apart
Energy in the Human Body
D. Conservation of energy in your body
1. Your body stores energy in the form of
fat and other chemical compounds.
2. Chemical potential energy from food
that is stored in your body is used to fuel
the processes that keep you alive
3. The food calorie is used to measure
how much energy you get from various
foods. One calorie is equal to about 4,180
J.
Discussion Question
1. What does the Law of Conservation of
Energy state?
Answer

Energy cannot be created or destroyed.
The total amount of energy in the universe
does not change.
Determine whether the italicized statement is
true or false. If the statement is true write true.
If the statement is false, write the correct term.
1.
2.
3.
4.
5.
6.
7.
8.
Energy in the form of motion is potential energy
The greater mass a moving object has, the more
kinetic energy it has
A rock at the edge of a cliff has kinetic energy because
of its position
Friction causes some mechanical energy to change to
thermal energy
Energy that is stored is kinetic energy
Mass is measured in Joules
Doubling an object’s velocity will double its kinetic
energy
Chemical potential energy is energy stored in chemical
bonds
9.
10.
11.
12.
13.
14.
15.
Thermal energy is energy stored by things that
stretch or compress
A book and a feather are sitting next to each other
on a shelf and have different potential energies
Two copies of the same book are in a book case.
One book is twice as high as the other. They have
the same potential energy
A toaster uses chemical energy to make toast
Mechanical energy is the total amount of kinetic and
potential energy in a system
When a plant falls from a window its thermal energy
is transformed into kinetic energy
The law of conservation of energy state that
although energy can change forms it can never be
created or destroyed