Transcript energy - CanScience

ENERGY
What do you think of when you
hear the word ENERGY?
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Food
Movement
Doing things
Working
Sunlight
Energy
Where do they get
the energy to go
down the hill?
Why is energy so important to us?
EVERYDAY ENERGY?
What types of energy do you encounter
everyday?
How does energy get from one place to
another?
It will either transform or transfer.
So what is ENERGY?!?!
Energy is NOT matter and is actually very
difficult to define...
Textbooks define it as …
“The ability to do work”
We will define it by providing examples of
energy and the effects it has on objects.
There are many different types of energy…
Types of Energy
ALL energy can be classified
as either Potential Energy or
Kinetic Energy.
Potential Energy is energy that is stored.
Kinetic Energy is energy of anything that is in
motion.
Gravitational POTENTIAL
Energy (GPE)
Gravitational Potential Energy (GPE) is the
stored energy of an object resulting from the
position of the object in a system.
GPE relies on the height of the object in the
system…the higher the object the more GPE it
has.
If you add GPE to KE you get Mechanical
Energy (ME). ME= GPE + KE
Kinetic Energy (KE)
Kinetic Energy (KE) - the energy of
motion. The energy associated with
moving objects is called kinetic energy
(KE), and is often referred to as the
most fundamental form of energy.
The size of the KE is determined by
an object’s speed and its mass.
Salem Nuclear Power Plant
Nuclear Power- Nuclear power
plants split the nuclei of
uranium atoms in a process
called fission.
The sun combines the nuclei of
hydrogen atoms in a process
called fusion.
Scientists are working on
creating fusion energy on
earth, so that someday there
might be fusion power plants.
Chemical Energy vs.
Nuclear Energy
Chemical Energy
• It is the energy that holds
electrons together that
move around the nucleus.
• Happens in the Electron
Cloud
• The energy can be released
when the bonds are broken.
• Small Amount of Energy
released
• Examples Digestion,
burning fossil fuels
Nuclear Energy
• It is the energy stored
in the nucleus of an
atom.
• Happens in the Nucleus
• The energy can be
released when the nuclei
are combined or split
apart.
• Large amount of Energy
released
• Examples Sun,x-rays,
Nuclear Power
What’s the Difference between energy
transfer and energy transformation?
Give an example of each.
Energy transfer is when the same energy is
transferred to another object.
When you kick a soccer ball down the field
with your moving leg! (transferring energy
from your leg to the ball)
Energy transformation is when one energy
type changes into another type of energy.
A rollercoaster that is stopped on top of the
hill rolls down the track. (PE-KE)
Energy in Systems
Energy can move from place to place or
change from one type to another…
Energy transformation – is changing
from one type of energy into a different
type of energy.
Energy transfer - is how the same type
of energy is passed from one object to
another object.
Dropping Golf Balls ...
You will drop a golf
ball and a fuzzy ball
from four different
heights (25cm,
50cm, 75 cm and
100cm) looking for
evidence of energy
by a change that is
produced by each
one.
Let’s Investigate
At each lab station you will find a piece of
paper with 7 Questions and a set of directions
from A-D. (Do NOT write on these sheets.)
You must do these in order… so if some
Questions come first, answer the question
BEFORE going on to the direction steps!!!
Answer the questions on the dry erase board
neatly. You may discuss the answers as a
group, but do NOT copy answers from other
groups…write your own!!!
Set up a Data Table
1. Make a data table
2. One column for the
golf ball and one
column for the fuzzy
ball.
3. Use little ruler to
measure the width of
the crater in cm.
4. Then Use the ruler to
smooth the sand.
5. Record your answers.
6. Clean up when you
are finished! Answer
post lab questions.
Heights
Height
(cm)
25
50
75
100
Golf
Ball
Fuzzy
Ball
Width
of
Crater
(cm)
Width
of
Crater
(cm)
Investigation Results
1.) The golf ball does not have any KE
since it is not moving. It does not have
the ability to move on its own due to its
position (sitting in the sand) so it does
not have any GPE. If KE = 0J and GPE =
0J then ME is also 0J!!!
2.) The golf ball now has GPE b/c it is
above the ground… it now has a height of
25cm!!! It does not have KE though since
it is not moving.
Investigation Results
3.) The golf ball got its energy from the
person who picked it up and moved it to
a height!!! The person TRANSFERRED
energy to the ball from themselves when
they lifted it!!!
This energy came from the person’s
muscles. The muscles got their energy
from the food you ate.
Tracing this flow of energy is called an
ENERGY CHAIN.
Investigation Results
4.) The ball dropped from the highest
point = 100cm caused the biggest crater.
5.) The variable that changed here was
the MASS of the ball. Everything else
remained constant (stayed the same).
The craters produced by the hollow
ball w/ less mass were smaller.
Mass affects GPE and KE!!!
Investigation Results
6.) Both of the balls hit the sand at the
same speed!!! (In other words, they fall
at the same time!!!)…Watch I’ll show
you…
The difference between the two balls
is the amount of energy!!! The more
massive ball possesses more energy!!!
Investigation Results
7.) The big point you should have concluded
is that MASS affects both GPE and KE.
You should have also concluded that
the higher the release point, the faster
the ball will be traveling when it hits the
sand. Gravity speeds up ALL falling
objects at the same rate (9.8 m/s2).
The greater the speed of the object
when it hits the sand, the greater the KE.
LAW OF
CONSERVATION
of
ENERGY
In the golf ball investigation, can we
account for all the energy in the
system?
Basically, if we add up all the PE, KE
and any friction, will it equal the
total energy (TE) in the system?
Yes, scientific evidence leads us to
believe that ALL of the energy in any
example can be accounted for!
But it is not always easy in an open
system.
LAW OF CONSERVATION
of ENERGY
Energy cannot be created or
destroyed; it can only be transformed
or transferred.
Total Energy is all the energy in a system
The TOTAL ENERGY (TE) will always
stays the same!!!
TE = PE + KE + heat
LAW OF CONSERVATION
of ENERGY
The TOTAL ENERGY of a system can be
measured by adding PE + KE + Heat.
TE = KE + PE + heat
Q: Where does the heat come from???
A: Friction!!! (Rub your hands together and
see what happens!!!)
LAW OF CONSERVATION
of ENERGY
TE will equal the GPE at the
highest point in a system!
TE=GPE at the highest point
100 Joules of energy to start
100 Joules of energy at the
end!
Equal at the mid point!
“What you put in, is what you
get out!”
(TE) NEVER CHANGES in a
system!
A
B
C
LAW OF CONSERVATION
of ENERGY
Let’s look at the pendulum swing. Will it
continue to swing with same amount of energy
over time?
Why won’t the beginning energy ever equal the
end energy???
Hint: Can heat be contained in an open
system?
NO… please remember that energy is not
destroyed, but some of it can escape from the
system to the surroundings in the form of heat
from the rope.
LAW OF CONSERVATION
of ENERGY
This is why no system will ever be
100% efficient…
Meaning the beginning energy will
never equal the end energy…
There is no such thing as a
frictionless system!!!
2. In an energy chain, only KE and GPE are to be
included.
AGREE
DISAGREE
As energy is transferred and transformed in a
system, some of the energy is lost.
AGREE
DISAGREE
Work is the same thing as energy.
AGREE
DISAGREE
If something has a lot of energy, it also has a lot
of power.
AGREE
DISAGREE
ENERGY CHAINS
Since energy is transferred and
transformed all the time, it is helpful to be
able to track the “flow” of energy in
systems.
A map of what happens to energy, where it
goes, and how it changes is called an
Energy Chain.
Energy chains can be created using words,
pictures, arrows, or any combination of
things that show the movement of energy in
an example.
Energy Chains
Can you think of how the energy flows
through a car?
What would you start with?
What types of energy transformations
are happening?
Energy Transfer and
Transformation
Thermal Energy
Thermal
Mechanical
Electrical
Chemical
Kinetic Energy
Can you construct an
Energy Chain for a
person hitting a softball
to the outfield?
Hitting a softball into
the outfield
1.
2.
3.
4.
5.
6.
7.
Chemical E to pick up bat 8. Ball hits ground (Friction)
from food.
9. Balls KE is transferred to dirt
Ball has PE in the air
as it flies up.
Ball throw in air
transform from PE to KE
Bat hits ball transfers
KE to ball
Ball increases KE
Gravity pulls on ball
Air resistance slows ball
down
Constructing
Energy
Diagrams
Using Font Size
Predict what this car is doing?
Coming to a stop!
The KE is deceasing over time as it is being
transformed in heat and PE energy.
A car stopping as a
standard Bar Graph
Using Circle Graphs
Circle graphs can be used to illustrate energy
flow. Each form is a represented by a portion
of the circle. Multiple circle graphs can
illustrate how the amount of energy in each
form changes over time.
Circle Graph
Examine what is happening in these circle
graphs?
What do you notice at interval 4?