Download Int. Sci. 9 - Energy Powerpoint

What is energy?
• “the ability to do work”
• The combination of energy and matter
make up the universe:
– Matter is substance, and energy is the
mover of substance.
Energy is
nature’s way of keeping score.
We sense energy only
when the score
changes,
either a transformation
from one form of
energy to another,
or a transfer of energy
from one point to
another.
Nature of Energy
 Because
of the direct
connection between energy and
work, energy is measured in
the same unit as work: joules
(J).
 In addition to using energy to
do work, objects gain energy
because work is being done on
them.
How is all energy divided?
All Energy
Potential
Energy
Gravitation
Potential
Energy
Elastic
Potential
Energy
Chemical
Potential
Energy
Kinetic
Energy
Potential
• energy of position
or energy in
storage.
– Water behind a dam
– Hammer over head
– Food on the plate
Kinetic
• energy of motion,
the form capable of
doing work
– Flowing water
– A falling hammer
– Electrons regenerating
ATP in a bio’l cell
PE = mgh
• m = mass (kg)
• h = height (m)
• g = accel due to
gravity
– (9.8 m/s2)
The Law of Conservation of
Energy
• Energy cannot be created or destroyed; it
may be transformed from one form into
another, but the total amount of energy
never changes.
What is Gravitational Potential
Energy?
o Potential energy
due to an object’s
position
Don’t look down,
Rover!
Good boy!
o P.E. = mass x
height x gravity
What is Potential Energy?
o Energy that is stored
and waiting to be
used later
What is Elastic Potential Energy?
o Potential energy due compression or
expansion of an elastic object.
Notice the ball compressing
and expanding
What is Chemical Potential Energy?
o Potential energy
stored within the
chemical bonds of
an object
What is Kinetic Energy?
o Energy an object has due
to its motion
o K.E. = .5(mass x speed2)
KE = 1/2 m v2
•
•
•
•
4 kg bowling ball
at 10 m/s
= .5 (4kg) (10m/s)2
= 200 J
•
•
•
•
.25 kg baseball
at 50 m/s
= .5 (.25kg) (50 m/s)2
= 312 J
Courtesy Jerry Ohlinger’s Movie Material Store
Work is done when a force is exerted over a distance.
Work
• is equal to the force that is exerted times
the distance over which it is exerted.
• W=Fxd
• The unit of work combines the unit of
force (N) with the unit of distance (m)
• Newton-meter (N-m) aka Joule.
You carry a 20 kg suitcase upstairs, a
distance of 4m. How much work did you
do?
• W=Fxd
• F = ma
• = (20 kg) (10m/s2) = 200 N
• W=Fxd
• = (200 N) (4m)
• = 800 J
Power
• measures the rate of work done or the
rate at which energy is expended.
• Power is the amount of work done,
divided by the time it takes to do it.
• Power (watts) = work (joules) / time
(sec)
• P = W/t
Power
• Work performed equals energy expended,
• Power (watts) = energy (joules) / time
(sec)
• The watt is defined as the expenditure of
1 joule of energy in 1 second.
(75 watt light bulb consumes 75 J/sec)
Kinetic Energy Review




The energy of motion is called
kinetic energy.
The faster an object moves, the
more kinetic energy it has.
The greater the mass of a moving
object, the more kinetic energy it
has.
Kinetic energy depends on both
mass and velocity.
Potential Energy

Potential Energy is stored energy.


Stored chemically in fuel, the nucleus
of atom, and in foods.
Or stored because of the work done on
it:
Stretching a rubber band.
 Winding a watch.
 Pulling back on a bow’s arrow.
 Lifting a brick high in the air.

Kinetic-Potential Energy Conversion
Roller coasters work because of the energy that is
built into the system. Initially, the cars are pulled
mechanically up the tallest hill, giving them a great
deal of potential energy. From that point, the
conversion between potential and kinetic energy
powers the cars throughout the entire ride.
Kinetic vs. Potential Energy
At the point of maximum potential energy, the car has
minimum kinetic energy.
Important formulas and units
Quantity
Force
Work
Energy
Power
Definition
mass x accel.
force x distance
power x time
work / time
Units
newtons
joules
joules
watts
Ex. Problem on Power:
• Your CD system, uses 250 watts of
electrical power.
• You play it for 3 hrs. How much energy
used? About how much would it cost? If
one kWh is $.08.
• Energy (J) = power (watts) x time (sec) =
(250w) (3hr) = 750 Whr = .75 kWh
• The cost = 8 cents/ kWh x .75 kWh
• = 6 cents
Power = work / time
• . Two physics students, Will N. Andable
and Ben Pumpiniron, are in the
weightlifting room. Will lifts the 100-pound
barbell over his head 10 times in one
minute; Ben lifts the 100-pound barbell
over his head 10 times in 10 seconds.
Which student does the most work? Which
student delivers the most power?
6 fundamental forms of energy
1.
2.
3.
4.
5.
6.
mechanical energy
Thermal (heat) energy
electromagnetic energy
electrical energy
nuclear energy
chemical energy
What is the source of our
energy?
• The source of
practically all
our energy is
the Sun.
What is Mechanical Energy?
o Energy due to a
object’s motion
(kinetic) or position
(potential).
The bowling ball has
mechanical energy.
When the ball strikes
the pins, mechanical
energy is transferred
to the pins!
Mechanical Energy
 When
work is done to an
object, it acquires energy.
The energy it acquires is
known as mechanical energy.
Mechanical Energy
 When
you
kick a
football, you
give
mechancal
energy to the
football to
make it move.
Mechanical Energy
When you throw a
balling ball, you
give it energy.
When that
bowling ball hits
the pins, some of
the energy is
transferred to the
pins (transfer of
momentum).
Examples of Mechanical Energy
What is Electromagnetic
Energy?
o Light energy
o Includes energy from
gamma rays, xrays,
ultraviolet rays,
visible light, infrared
rays, microwave and
radio bands
Electromagnetic Energy

Power lines carry electromagnetic
energy into your home in the form of
electricity.
Electromagnetic Energy



Light is a form of
electromagnetic energy.
Each color of light (Roy G
Bv) represents a different
amount of
electromagnetic energy.
Electromagnetic Energy is
also carried by X-rays,
radio waves, and laser
light.
What is Electrical Energy?
o Energy caused by
the movement of
electrons
o Easily transported
through power lines
and converted into
other forms of
energy
What is Chemical Energy?
o Energy that is
available for release
from chemical
reactions.
The chemical bonds in
a matchstick store
energy that is
transformed into
thermal energy when
the match is struck.
Chemical Energy
 Fuel
and food
are forms of
stored
chemical
energy.
Examples of Chemical Energy
What is Thermal Energy?
o
Heat energy
o The heat energy of an
object determines how
active its atoms are.
A hot object is one whose atoms
and molecules are excited
and show rapid movement.
A cooler object's molecules and
atoms will show less
movement.
Nuclear Energy
 The
nucleus
of an atom is
the source of
nuclear
energy.
Nuclear Energy


When the nucleus splits (fission),
nuclear energy is released in the
form of heat energy and light
energy.
Nuclear energy is also released
when nuclei collide at high speeds
and join (fuse).
Nuclear Energy
The sun’s energy
is produced from
a nuclear fusion
reaction in which
hydrogen nuclei
fuse to form
helium nuclei.
Nuclear Energy
 Nuclear
energy is the
most
concentrated
form of
energy.
Perry Nuclear Power Plant converts nuclear
energy into electromagnetic energy.
QUIZ TIME!
What type of energy
cooks food in a
microwave oven?
ELECTROMAGNETIC
ENERGY
What type of energy is
the spinning plate
inside of a microwave
oven?
MECHANICAL ENERGY
QUIZ TIME!
Electrical energy is
transported to your house
through power lines.
When you plug an electric fan
to a power outlet, electrical
energy is transform into
what type of energy?
MECHANICAL ENERGY
QUIZ TIME!
What energy transformation
occurs when an electric lamp
is turned on?
ELECTRICAL ENERGY

ELECTROMAGNETIC ENERGY
What types of energy are shown below?
Mechanical and Thermal Energy
(Don’t forget friction)
What type of energy is shown below?
Chemical Energy
What types of energy are shown below?
Electrical, Mechanical and
Electromagnetic Energy
What type of energy is shown below?
Chemical Energy (yummy)
What type of energy is shown below?
Thermal Energy
What types of energy are shown below?
Mechanical, Electromagnetic,
Electrical, Chemical and Thermal
Energy
Energy conversions

All forms of energy can be
converted into other forms.


The sun’s energy through solar cells
can be converted directly into
electricity.
Green plants convert the sun’s energy
(electromagnetic) into starches and
sugars (chemical energy).
Other energy conversions



In an electric motor, electromagnetic
energy is converted to mechanical
energy.
In a battery, chemical energy is
converted into electromagnetic energy.
The mechanical energy of a waterfall is
converted to electrical energy in a
generator.
Energy Conversions

In an automobile
engine, fuel is
burned to convert
chemical energy
into heat energy.
The heat energy is
then changed into
mechanical
energy.
Chemical  Heat Mechanical
Kinetic-Potential Energy Conversions

As a basketball
player throws the
ball into the air,
various energy
conversions take
place.
Ball slows down
Ball speeds up
Law of Conservation of Energy


In 1905, Albert Einstein said that
mass and energy can be converted
into each other.
He showed that if matter is
destroyed, energy is created, and if
energy is destroyed mass is
created.
2
 E = MC
Vocabulary Words
energy
mechanical energy
heat energy
chemical energy
electromagnetic energy
nuclear energy
kinetic energy
potential energy
gravitational potential energy
energy conversion
Law of Conservation of Energy