Pictures from my lab notebook
ICWtB
Tuesday, July 15, 2014
Unit 8 Uniform circular motion
Unit 8 Circular motion
Important question is it
accelerating before we answer it
directly take a mental snap shot when it is farthest to the left. Draw a force
diagram for the stopper at that instant.
Any way to get the forces
to balance?
Is it accelerating up and
down (no it is moving horizontally. So
is it accelerating up and down? No
Discrepant event rubber
stopper where to release so that a person can catch it.
Draw a motion map for an
object moving in a circle.
Rules
Velocity arrows always
point tangent to the circular path
Acceleration arrows point
inward toward the center
Funbal always points
inward toward the center
Demo of people shoulder to
shoulder going in a circle getting into angle of lean
Examples of where you
have to lean to go in a circle?
What will influence the
force needed to cause something to move in a circle?
Look up in the google
what the coefficient is. The question is
what to look up in the google.
Centripetal force is a
nick name.
Funbal=Fnet=Fcent
Go over Unit 8 Worksheet 1
Remember our bodies are
not velocity meters but accelerometers
How do we know that the
unbalanced force goes down because the acceleration is toward the center of the
circle.
Sunday, July 13, 2014
Unit 7 Energy
Unit 7 Energy
This is a difficult
concept since we have all experienced and heard about this for a long time but
we don’t have a firm grasp of what energy really is
Have students give their
ideas of what energy and work are.
What is energy What
is work
Ability to do work transfer
of energy
Power
Ability to produce change
Fossil fuels
Nuclear
Red bull
5 hours
Light
Heat
We did a little aside to
cover the idea of gravitational field to be used later on in this unit I assume
I’m wondering how to
incorporate the field concept into the modeling because I think it is a part of
NGSS.
On Earth
Gravitational Field 10 N/kg
is the gravitational field strength
sometimes represented by 10N/kg = g
On the moon (trusting
people who know stuff) g=1.6N/kg, Mars 4 N/kg
Someone also asked the
following question and so we took some time on this as well.
Why do objects of
different masses fall with equal acceleration?
The earth pulls on more massive objects with more force and more massive
objects resist changes in motion more..
Energy resumption We already have an idea of force and energy
before “this isn’t your first day as a human”
Examples of energy
Electrical
Mechanical
Chemical
Nuclear
Wind
Solar
Green
Geothermal
Food
Dark
Kinetic
Potential
Electromagnetic
Elastic
Tidal
Thermal
Light
Heat
1st rule of
energy—All energy is stored energy! You must name where/how it is stored We
will start here (Give this as a place to
start since we really don’t know anything)
Go to the list and try to
fill it in with the where/how
(I can really see where
students would be apprehensive to answer in fear of being wrong)
We roll out some
analogies. Currency—If I owed you money
how many different ways could you pay?
Information—Can you hold
it in your hand? No could you put it in a book, oral, computer . . .
MP3—is it an actual
physical thing? No but can you store it ?
Energy is
1.
Stored
2.
Transferred
3. ? Filled in later with conserved
Visual representation
Use a pie chart to
represent 100% of the energy.
Group those that are
released to the environment.
What about a cart going
up a ramp and stopping. Where did it go
at the end? The gravitational field
Adding the agent of
change to the pie charts. Then you can
add the question what is doing work (the agent of change)
The dropper popper discrepant
event was discussed. This has a lot of
potential I think
Fenyman had the same
problem with the idea of energy it is just like an accounting system
Go back to the 3 things
that are important about energy
1.
Stored
2.
Transferred
3. Conserved
Bar charting is limited to beginning and end of an event
Between the two sets of
bar charts show the system
If something is not
included in the system then it still needs to be accounted for so put it
outside the system and put the number of blocks associated with it.
Paradigm lab horizontally
stretching a spring
Discussion F=(slope)x+0
How does the slope change
the farther you stretch it?
Elastic limit.
If you stretched the
spring did you store energy? If you did
then the graph probably shows it somehow?
Things to examine on any
graph
1.
Axes
2.
Slope
3.
Intercepts
4.
Values/ points
5.
Shape
6. Area
Derive the formula and
then calculate the energy stored in the spring.
1. Compare the energy in the spring to the speed
of a cart (have different groups use different masses)
Finish the 3 lab E vs v
E vs h
And E vs d
The leap from F-d graph
for a spring to area under the curve requires a certain amount of hand waving as does a number of things from this section.
How does the elastic
energy of the spring compare to the kinetic energy of the cart? We know this because energy is conserved
First of all we can say
that the Elastic energy is equal to the gravitational energy.
Is It reasonable that the
gravitation field energy would be related to the gravitational field strength.
Lets work the magic How does the elastic energy in the spring
compare to energy lost to surrondings.
They have to be the same.
D=( )ELS
Joule (J) it is a derived Unit which is a Nm Pushing a
cart 1m with a 1N force gives the cart 1 J of energy
Relate the lab of E vs
skid to the energy lost to surroundings
Possible practicum block and spring so that the block slides to
the end without going over then end.
Extras
@ brybatt physicsmodeler.blogspot,com about standards
based grading.
Phet simulations skate
park show pie chart
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