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[Phys-L] modeling

The ASU site is the most complete. There is also the AMTA organization (American Modelers Teaching Association or something) at modelinginstruction.org . The amta group is working with asu & jane jackson in an effort to make modeling sustainable long term. If one person leaves a job, the organization will still exist with board members etc...



The modeling method makes an adaptation of the Karplus Learning cycle. The Modeling Cycle has two major stages. Model development and Model deployment. A few quick basics.

The Development stage has four main sections: description, formulation, ramification and validation. Those terms aren't usually used with students, but as I look at it now, maybe I will use them more often. Kids aren't given an equation. They do a lab to develop the mathematical model. Then they learn when & how to use which model.



A quick kinematics example using a fairly common lab with modeling twists. The lab below would be called a "Paradigm Lab."

Use a battery powered car that travels at constant velocity. Ask kids what we can measure. They often discuss many topics: speed, acceleration, color, momentum, weight... Narrow the question to "how can we describe the motion of the car?" They'll still claim acceleration velocity momentum and so on. Since we don't have tools to directly measure acc and velocity in class, we choose to record position and time.

Through questioning help them plan a method to set time and measure position of the car as it changes position. As they are in groups, I assign origins and directions to each group. Some start at x=0, some at +2, some at -1. Different groups travel in the + or - direction.

They record then plot x vs t graphs.

Some cars have 2 batteries. Some cars have 1 battery and 1 slug / space filler.

Each group presents they graph and the equation that best matches their data. They do this on a 2' x 3'whiteboard.

They are to answer questions like:

what is your slope?

what does your slope represent?

is possible, how could you change your slope?

what is your y-intercept?

what does your y-intercept represent?

if possible, how could you change your y-intercept?

On different labs we would also ask:

what is the area under the curve of your graph?

what does the area under the curve of your graph represent?

what are the units of measure for the area under the curve of your graph?



From the lab, students 'create' the model xf=vt+xo



After this, in the model development stage, students will use motion maps & graphs to determine the equation / mathematical model for the motion of the object. They practice constant velocity for a while.



The unit usually ends with a "Deployment Lab."

An example for constant velocity (one I attempt to do with just one setup for the class):

Cops and robbers or some other named scenario... A red car leaves position x and goes in the + direction. When the red car gets to location x=1.5m, one blue car begins to chase it down from behind (leaving from x=0) while a second blue car attempts to cut it off from the front. The second blue car goes in the -x direction leaving from position x=3m.

Which blue car will catch the red car first?

The kids need to determine the velocity of each car. They can solve the problem graphically or mathematically (thru equations). They can not simply attempt trial and error.



The homework for each unit really hits at concepts and the relationship btn graphs and equations.





Most folks that model also spend a lot of time linearizing data. Whatever data the students collect, they linearize. If x is proportional to t then it is constant velocity. If x is proportional (linear) with t^2, then the velocity changes and there is a constant acceleration. This linearization is a big part of modeling physics for most modelers.



Both the asu and modelinginstruction site have the 1st semester mechanics materials available for free.



Have a good one.



Paul.









-----Original Message-----
From: Phys-l [mailto:phys-l-bounces@phys-l.org] On Behalf Of Anthony Lapinski
Sent: Tuesday, July 30, 2013 10:50 AM
To: Phys-L@Phys-L.org
Subject: Re: [Phys-L] [SPAM] Re: The Make-Believe World of Real World Physics



I've heard about modeling. What are some good online sources for this?



Actually, I often make up my own math problems that are very interesting and practical. They still have to read the problem, sift out the info, and apply the appropriate equations. I also tell them (especially my honors

students) that the problems on the test will be ones they have never seen before. So they really have to understand physics in order to do the math.

They must rely more on thinking and less on memorization. I tell them, "How you think is more important than what you know." And they can get partial credit on the math. My MC questions are much harder for them as they involve all concepts/applications, and I also give partial credit (if they circle two answers and one is correct).







Phys-L@Phys-L.org<mailto:Phys-L@Phys-L.org> writes:

The Modeling Physics approach does a LOT to resolve student graphing

challenges. A lot.

Learning the modeling method is well worth the time and effort. I

highly recommend giving it a shot.

Students can do the math because most of the math problems don't

require any thought about physics. They have a 3 or 4 variable equation

(maybe 2

eqns) and they plug n chug. It is often done with no physics thought.



Paul.







.:. Sent from a touchscreen .:.

Paul Lulai









-------- Original message --------

From: Anthony Lapinski <Anthony_Lapinski@pds.org<mailto:Anthony_Lapinski@pds.org>>

Date: 07/30/2013 9:59 AM (GMT-06:00)

To: Phys-L@Phys-L.org<mailto:Phys-L@Phys-L.org>

Subject: Re: [Phys-L] [SPAM] Re: The Make-Believe World of Real World

Physics





Allow me to jump in here about graphs. I think kids know how to graph

functions in their math classes. Then they come to physics, and it's a

whole new ball game. So difficult for them, especially with slopes.

Then, I give them a few constant slope lines on a "d-t graph" and ask

which has the highest acceleration. They just confuse the axes and

think it's a v-t graph (like something they've seen before). Some just

never understand graphs. Kids generally find math problems the easiest.

Concepts and graphs are more difficult.



Not sure what the solution is. Kids have difficulty thinking in school

these days, which is why they find physics challenging. It requires

them to think in ways they never have before. And thinking requires

effort. And they have other classes, XC activities, and social lives.



What to do???







Phys-L@Phys-L.org<mailto:Phys-L@Phys-L.org> writes:

I think there is real value in getting students to use graphs to

understand situations and solve problems. But first they have to

understand graphs, and I don't think enough time is spent in math or

physics on that. Do students understand what the points on the graph

represent, do they understand what horizontal and vertical intervals

represent? How do we know they do understand.

These graph solutions can be done with constant velocity problems

first and then advanced to more complicated situations as the student

understanding develops.

Average velocity also has extra meaning when you look at graphs and begin

to talk about slope. I suspect your concern has more to do with the

abstract nature of the way the problem is presented, rather than about

the content. What say you?



joe

On Jul 30, 2013, at 8:44 AM, Philip Keller wrote:



I agree. These are nice math puzzles but they barely feel like

physics

to

me. They have the "if Mary can mow a lawn in 40 minutes..." feel to

them.

I see this particular type of item as part of the black hole of

kinematics. I would much rather skip this and spend that time

trying

to

get my students to use graphs to solve problems rather than formulas.





On Mon, Jul 29, 2013 at 9:40 PM, Paul Lulai

<plulai@stanthony.k12.mn.us<mailto:plulai@stanthony.k12.mn.us>>wrote:



I think this question (how fast / far to have a certain avg speed)

is

a

lot of work that isnt worth the payoff and is also a bit of a trap.

It feels like we are baiting them into trying to do it incorrectly.

I am sure there are science & technical folks that do a lot with

average

speed, but we do next to nothing with it in high school, except ask

trick

questions like this one. I suppose it is a way to check the

difference

btn

speed and the vector nature of velocity. It just seems like there

would be

other ways that could check the same conceptual point and be less

misleading.

I don't do much at all w avg speed. While I am sure it can be

helpful

in

some situations, this isnt an area I am going to go crazy preparing

for.



Paul



.:. Sent from a touchscreen .:.

Paul Lulai









-------- Original message --------

From: Anthony Lapinski <Anthony_Lapinski@pds.org<mailto:Anthony_Lapinski@pds.org>>

Date: 07/29/2013 6:51 PM (GMT-06:00)

To: Phys-L@Phys-L.org<mailto:Phys-L@Phys-L.org>

Subject: Re: [Phys-L] [SPAM] Re: The Make-Believe World of Real

World Physics





Makes sense.



Acceleration is hard for kids. I begin the course with speed,

average speed, velocity, etc. Another "basic" problem/idea kids in

my class

get

wrong is about average speed:



Must average 200 mph over 2 laps. After one lap, you've only

averaged

150

mph. What must be your average speed for the second lap?



Many want to say 250 mph as they want to just average the speeds.

They forget the definition that avg speed = distance/time. Even

after doing problems in class and for homework, they continue to

miss this

question

(and variations of it) on the test. Physics requires a different

way

of

thinking about the world.



You can simplify this with a related question:



On a trip to New York. One way is 60 miles. 60 mph going there and

30

mph

coming back. Is the avg speed for the entire trip less than equal

to,

or

more than 45 mph?



It's a great peer instruction question as the math is relatively

easy

to

do in your head, and those that understand the problem can explain

it

to

others. Still challenging for some. Very interesting discussions to

hear

in the classroom!



So do others teachers have similar experiences with these types of

average

speed problems?





Phys-L@Phys-L.org<mailto:Phys-L@Phys-L.org> writes:

I can certainly envision lots of students claiming the

acceleration

at

the peak is zero. However, i think this answer comes from

students trying to memorize physics points rather than think about

and analyze physics. In my experience, students that answer a=0

remember there is something unique about the top. They remember

something is zero and

they

go with a =0 since we are asking them about a.

If we ask them if there velocity at the peak will remain constant,

few

will say /yes the velocity will be 0 and will stay 0 at the top

forever

and the ball will never fall/.

Our challenge is to get them to analyze the scenario and avoid the

temptation to answer reflexively.

In my opinion, that is the challenge w a lot of the challenging

and trick/tricky physics questions students encounter in their

first

course.



Have a good one.

Paul.



.:. Sent from a touchscreen .:.

Paul Lulai









-------- Original message --------

From: Kirk Bailey <kirkbaile@gmail.com<mailto:kirkbaile@gmail.com>>

Date: 07/29/2013 5:01 PM (GMT-06:00)

To: Phys-L@phys-l.org<mailto:Phys-L@phys-l.org>

Subject: Re: [Phys-L] The Make-Believe World of Real World Physics





I can't remember where or when, but I know I read that the number

one misconception (based on how many students still missed it at

the end

of

the

course) was the acceleration of an object thrown straight up at

the

peak

of

its trajectory. Just understanding that it isn't zero at the top

is

a

non-trivial objective, and I don't see it as an easy question in

any student universe.





On Mon, Jul 29, 2013 at 4:19 PM, Anthony Lapinski

<Anthony_Lapinski@pds.org<mailto:Anthony_Lapinski@pds.org>>wrote:



Right. And a student in a physics class should answer it

differently (correctly). Acceleration = rate of change of

velocity = gravity = constant (in free fall).



Unless, of course, I am missing something or in a different

universe.





Phys-L@Phys-L.org<mailto:Phys-L@Phys-L.org> writes:

Folks on the street indeed are likely to think of acceleration =

speeding

up and deceleration = slowing down. therefore acc at top = zero.



Every beginning physics student should be able to think of the

velocity

graph with it's slope and areas included.



On Jul 29, 2013, at 3:36 PM, John Denker <jsd@av8n.com<mailto:jsd@av8n.com>> wrote:



You might be a redneck physicist if you buy 48 cans of Big

Flats beer and cool them off using liquid nitrogen.





On 07/29/2013 07:29 AM, William Maddox wrote:

In this universe the acceleration of a ball at peak question

would

not be considered ill posed in the context of a physics test

following chapters on projectile motion and gravity.



Congratulations on living in such a nice universe (A).



Meanwhile, there are plenty of people on this list who live in

a different universe (B), where students find this question

hard or at least counterintuitive.



I reckon this list is extremely valuable, because it allows us

to recognize and discuss the difference between these two

universes.

-- Why is this an easy question in one universe but not the other?

-- Can we move everybody from universe (B) to universe (A)?

-- If so, how?



I remind everybody yet again that many things that seem hard at

the beginning of the road seem easy (and are easy) at the end

of the road.



=============================



Physicists tend to write as little as they feel necessary.



... which can be a big part of the problem, if they misjudge

what is "necessary". This is known to be a problem whenever

experts are talking to non-experts, including students.

Miscommunication makes things hard, even things that ideally

"should" not be hard.

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--

Kirk Bailey

Never use a big word if a diminutive synonym is as efficacious.

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Joseph J. Bellina, Jr. Ph.D.

Emeritus Professor of Physics

Co-Director

Northern Indiana Science, Mathematics, and Engineering Collaborative

574-276-8294

inquirybellina@comcast.net<mailto:inquirybellina@comcast.net>









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