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Matter and Energy
Energy
= the ability to do
work.
Chemistry:
The study of matter and its
changes
Matter:
EVERYTHING
MATTER
ENERGY
Physics
The study of energy and forces
Energy
The ability to change or move matter.
Anything that has mass and
volume
Nature of Energy
Energy
Energy is all around you.
You hear energy as sound, you see energy
as light, you can feel energy in wind.
Living organisms need energy for growth
and movement.
You use energy when you hit a tennis ball,
compress a spring, or lift a grocery bag.
The energy released by
a supernova is capable
of destroying a nearby
solar system in just a
few hours. A supernova
is one of the greatest
concentrations of
energy in the universe.
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Types of Energy:
ENERGY
Types of Energy:
The sum of all the kinetic energy and
potential energy in a system is called the
Kinetic Energy
Potential Energy
(Energy of Movement)
(Stored Energy)
Thermal Energy
(Heat)
Gravitational
Potential Energy
Radiant Energy
(Light)
Elastic
Potential Energy
TOTAL MECHANICAL ENERGY
KE + PE = TME
Because energy is the
ability to do work, it
is measured in
Joules.
Units of Energy
= Joules (J)
Elastic
Potential Energy (EPE)
= Energy
stored in a
stretched or
compressed
material
(spring,
rubber band,
bungee cord,
bow, etc.)
2 Types of Energy:
Kinetic Energy (KE)
(Energy of Movement)
and
Potential Energy (PE)
(Stored Energy)
Gravitational
Potential Energy (GPE)
= Energy stored
due to height
from the
ground
(depends on
weight and
height)
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We will concentrate on
Gravitational Potential Energy
Kinetic Energy (KE)
gravitational PE = Weight x Height
The energy of motion.
Remember, Weight is defined as
W = mg
The faster the object
moves – the more kinetic
energy.
The motion of molecules is
what causes HEAT, so:
So, gravitational PE can be written as (mg)
(mg) x h
PE = mgh
Kinetic Energy
KE depends on
mass and velocity.
•KE = ½(mass x velocity2)
units:
HEAT is a form of kinetic energy.
Formulas:
Kinetic Energy:
KE  1 2 mv 2
PE = mgh
v
2 KE
m
m
2 KE
v2
= kg m2/s2
= Newton*meter
KE = ½
mv2
= Joules
Math Skills:
Potential Energy:
Weight = mg
(g = 9.8 m/s2)
PE
m g h
PE Sample Problem:
Order of Operations and the KE formula:
KE  1 2 mv 2
v
2 KE
m
2 KE
m 2
v
1. Square Velocity
2. Multiply by mass
3. Multiply by 0.5
1. Multiply KE by 2
2. Divide by mass
3. Take the square root
1. Parentheses first;
square the velocity
2. Multiply KE by 2
3. Divide by your
answer from step 1.
This person, who
weighs 725
Newtons, is
currently 20.0
meters above the
ground. What is
their gravitational
PE ?
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PE Sample Problem:
KE Sample Problem:
This coaster must
have a PE of no
more than 824,000
Joules to survive
this 12.0 meter
drop. What is the
greatest mass the
coaster can have?
KE Sample Problem:
This roller coaster has a total of
604,800 J of kinetic energy when it
is travelling at its fastest, 12 m/s .
What is the mass of the coaster?
This 8,200kg
roller coaster
is moving at
7.6 m/s.
What is the
kinetic energy
of the
coaster ?
KE Sample Problem:
This 45,000kg
roller coaster has
a total of
840,000 J of
kinetic energy.
What is the
velocity of the
coaster ?
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Total Mechanical Energy
= the total energy of a system
KE + PE = TME
Conservation of Energy
Energy MAY be converted from one form to another.
Energy cannot be created or destroyed.
•Energy MAY be
converted from one
form to another…
…but the total
mechanical energy
of a system remains
the same.
Energy Transformation for a Dart
Here, gravitational potential energy is converted
to kinetic energy, but energy is conserved;
the total mechanical energy (TME) remains unchanged.
Energy Transformation on a Roller Coaster
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How High Will It Go?
v=0
KE = 0
PE = max
PE = ME
ME = PE h=max = KE h=0
h=0
PE = 0
KE = max
KE = ME
KE + PE = ME
Energy Transformation for a Pendulum
Energy Transformation for a Dart
The skiier begins at an elevated position, thus possessing
a large quantity of potential energy (i.e., energy of vertical
position
This energy state is maintained until the skiier meets a
section of unpacked snow and skids to a stop under
the force of friction
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