Transcript Notes 12 – Forms of Energy Part 1 States of Energy Energy exists in two basic states: 1.

Notes 12 – Forms
of Energy Part 1
States of Energy
Energy exists in two basic states:
1. potential
2. kinetic
Potential energy is stored energy
Kinetic energy is motion energy
Potential and kinetic are NOT
OPPOSITES
What is Potential Energy?
Stored energy that must be released
Energy that could be used to do work
but isn’t yet
It is energy an object has because
of:
– its position: book held above your head
– its shape: stretched rubber band
– Or its condition: charged battery
What is Kinetic Energy?
The energy an object has because
of its motion
It depends on 2 things:
1. Mass
2. Velocity
An aircraft carrier moving 30mph
has tremendous kinetic energy
A water molecule moving 10mph
has little kinetic energy
Potential or Kinetic?
A
A
A
A
A
A
A
A
rolling ball
bow with an arrow ready to fire
pile of fire wood
falling avalanche
tank of gasoline
student walking to class
flying bird
chicken patty
Potential energy comes in many
forms:
1.
2.
3.
4.
Gravitational Potential Energy
Elastic Potential Energy
Chemical Energy
Nuclear Energy
What is gravitational potential
energy (GPE)?
Gravitational Potential Energy energy stored in an object because
of its potential to fall and do work as
it falls
The heavier the object and the
further it can fall, the more potential
it has to do work
GPE = weight x height
Gravitational Potential (GPE)
GPE is released as
an object falls
GPE sample problem:
How much GPE does a 100N rock
have if it is 20m above the ground?
GPE = weight x height
GPE = 100N x 20m
GPE = 2000 Joules
Remember: all forms of energy are
measured in joules
Hydroelectric dams use GPE
We build dams to pile water high
The water flows down through the
dam with great force, turning
generators which produce electricity
What is Elastic Potential Energy
(EPE)?
Elastic Potential Energy (EPE) energy stored in an object that is
stretched or compressed
EPE can be stored in springs, elastic
bands, bouncy balls and bows.
Wind-up toys and old watches use
springs that store EPE
Elastic Potential Energy (EPE)
Elastic Potential (EPE)
EPE is released
when the object
snaps back to its
original shape
What is Chemical Energy?
Chemical Energy - energy stored
in chemical bonds between atoms
Chemical energy is released when
the chemical bonds are broken
EX. The bonds are broken during
combustion and digestion
What are some sources of
chemical energy?
foods
living things
fuels (anything
that burns)
batteries
What is Nuclear Energy?
Nuclear energy – energy stored in
the nucleus of an atom
Nuclear energy is released when a
nucleus is split or when nuclei join
together and become one new
nucleus.
Splitting is called fission
Becoming one is called fusion
What are some sources of
nuclear energy?
Plutonium in
nuclear weapons
Uranium in nuclear
power plants
The Sun and all
stars
Notes 13 – Forms of
Energy Part 2
Kinetic energy comes in many
forms:
1. Mechanical Energy
2. Heat Energy
3. Light Energy
4. Sound Energy
5. Electricity
What is mechanical energy?
Mechanical Energy– motion energy
of objects and substances
Moving machine parts that do work
have mechanical energy
Moving air and water (wind and
waves and currents) have
mechanical energy
Wind turbines use mechanical
energy to produce electricity
Moving objects can do work
What two things determine how
much work a moving object can do?
1.Its mass
2.Its velocity (speed)
Calculating mechanical kinetic
energy
To calculate the mechanical kinetic
energy of an object use the formula
below:
Kinetic Energy = ½ mass x velocity2
KE=½ mv2
m is mass in kilograms (kg)
v is velocity in meters per second
(m/s)
Sample Problem A
How much kinetic energy does a 20
kg fox have when it’s moving 2 m/s?
KE=½ mv2
KE=½ 20kg x (2m/s) 2
KE=½ 20kg x (2m/s x 2m/s)
KE=10kg x 4m/s
KE=40 joules
Sample Problem B
How much kinetic energy does the
same 20 kg fox have when it’s
moving 4 m/s?
KE=½ mv2
KE=½ 20kg x (4m/s) 2
KE=½ 20kg x (4m/s x 4m/s)
KE=10kg x 16m/s
KE=160 joules
What is heat energy?
Heat energy – The kinetic energy of
the particles within a substance
The hotter something gets the faster
its particles are moving
How is heat used to do work?
Heat is used to do work in an
internal combustion engine.
Spark plugs ignite gasoline inside the
engine.
The burning gas expands rapidly
pushing on the pistons
The moving pistons generate the
force that moves the car forward
What is light energy?
Light energy – the motion of waves
of electromagnetic energy
Light travels 186,000 miles per
second. That’s 7 ½ times around
Earth in a second.
It takes 8 minutes and 20 seconds to
reach earth from the sun.
Light as an energy source
Solar panels can
convert light into
electricity
The sun warms Earth
and provides the
energy living things
need to do work
What is electricity?
Electricity - Motion of
electrons through a
conductor
Electricity creates a
magnetic force that
electric motors use to
do work.
What is sound
energy?
Sound energy Pressure waves
moving through a
solid, liquid or gas
There is no sound
in space because
there is no matter
Law of Conservation of Energy
Energy cannot be created nor can it
be destroyed
The total amount of energy in the
universe remains constant
Energy can be transferred - move
from place to place
Energy can be transformed - change
from one form to another