Transcript Science 8 – Honors Section

Forms of Energy
QOD
1.
2.
What are the 5 types of energy?
Potential Energy and Kinetic Energy
are examples of what type of energy?
QOD- Answers
1.
What are the 5 types of energy?
1.
2.
3.
4.
5.
2.
Mechanical (moving energy)
Chemical
Electromagnetic
Thermal (heat)
Nuclear
Potential Energy and Kinetic Energy
are examples of what type of energy?
MECHANICAL ENERGY!
Forms of Energy

Mechanical – involves movement or the
potential for movement (2 forms)
1. Potential Energy – stored energy (PE)
-Not moving energy, but potential to move
-“Gravity” is the force acting on an object will
move if allowed to
-Impacted by  Mass, Gravity and “Height”
2. Kinetic Energy - Energy in motion (KE)

Impacted by - Mass and Velocity
How Energy is Related to Work…
How Energy is Related to Work…
Once the bow is released, what kind of
energy is found in the arrow?
Equations
 Potential Energy = (mass)(gravity)(height)

PE = m x g x h
Units of measurement





Mass = kg
Gravity = m/s2
Height = meters
Units for Potential Energy = Kgm2/s2 = Newton
meter or a JOULE (J)
Kinetic Energy = (1/2)(mass)(velocity2)
KE= 1/2 mv2

Units for Kinetic Energy = Newton Meters or
JOULES(J)
Equation Chart…
UPDATE EQUATION CHART WITH
POTENTIAL ENERGY AND KINETIC
ENERGY :)
Examples of PE and KE


Roller Coasters
Ski Mountains




Make mucho $ on PE & KE (you pay for PE-lift ticket)
Rain Forest Zip-Lines
Water Slides
Pendulums (physicsplace.com)
Examples of PE and KE

Can you think of any other real world
examples of potential and kinetic
energy???
Energy is Conserved
“Energy cannot be created or destroyed.”
Conservation of Energy


PE + KE = Total Mechanical Energy
Energy can transfer from PE to KE
Like a see saw battle (as one gains the other loses)
 Ex: If total energy = 100% at all times
…and there is 25% PE then there would be ___ KE

You can never gain more energy than
you started with…
you can’t gain more height without added force!
Converting Energy PE --> KE

In Theory… 100% PE
converts to 100% KE

So PE = KE

mgh = 1/2 mv2
Can you predict velocity based on height of
an object? (hint: solve for velocity)
Velocity = square root of (2*g*h)
Think Pair Share…
Energy Analysis Examples
(add these problems to your notes)
Roller Coaster Physics
1. Name two of the forces that affect the motion of the car while it moves
on the roller coaster.
2. Describe how the potential and kinetic energy of the car change as the
car rolls downhill.
3. Can the car reach point X on the track? Why or why not?
Physics Place Pendulum Fig.




1.
2.
3.
4.
www.physicsplace.com
Choose the top middle book (blue/green, 10th ed.)
User: bergmann12
Password: mustangs1
Does the total amount of energy in the
swinging pendulum change?
How are PE and KE related?
When the PE is very high, is it possible
for the KE to be very high as well?
When the pendulum has a KE of 82% of
the total energy, what would you assume
the PE of the pendulum to be?
Pendulum Calculation
1.
2.
If h = 20 cm and the purple ball has a mass of 10
kg, then what is the PE of this pendulum?
What would be the pendulum’s velocity at the
spot where the pendulum is at it’s lowest point?
Euler’s Disk
1.
2.
3.
What form of energy is occurring
here?
When the disk starts, does it have
more potential energy or kinetic
energy?
Does the disk gain energy as it
falls? Support your answer with
your thoughts.
Hot Wheels Ramp
1.
2.
Suppose the car is at rest at the
top of the ramp. Calculate it’s PE
and KE.
After the car is rolling down the
ramp, calculate it’s PE and KE at
the very instant before it is
stopped at the bottom of the
ramp.
Nerf Gun
1.
2.
How could you give the darts in
the gun PE (2 ways)?
What happens to the PE once you
pull the trigger of the gun?
Bowling Ball Pendulum
1.
2.
Will this demo hurt?
Explain your response to #1
http://video.google.com/videoplay?do
cid=1096316663622604841&q=bo
wling+ball+pendulum&hl=en
Penguin Race
Physics in Action
Penguin Race Questions
1.
2.
3.
4.
5.
What type of energy do the penguins acquire
as they climb?
What type of energy do the penguins acquire
as they slide down the track?
Work transforms energy from one form to the
other. What is doing the work as the
penguins slide down the track?
The D cell battery that powers the toy
provides what type of energy?
The penguins can climb due to energy
supplied by the dry cell battery.
What does the work in this energy
transition?
Penguin Race Questions
6.
7.
8.
9.
Energy is conserved in a closed system.
Does all of the dry cell energy go into
raising the penguins? Why?
Is the energy the penguins “acquire” by
climbing to the top of the ladder equal to
the total amount of energy at the bottom
of the track? Why?
Friction can do work. Lists all places that
friction exists in this toy.
Are the penguins at their “terminal
velocity” when sliding down the track?
How do you know?