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Easy Java Simulations (2001- ) => Questions related to EJS => Topic started by: lookang on February 24, 2011, 08:50:20 am



Title: can data builder do dflux / dt ?
Post by: lookang on February 24, 2011, 08:50:20 am
can data builder do dflux / dt ?

i am trying to design an activities something like modelling for learners to key in data function
slope = dflux / dt

and compare with emf graph

to conclude - slope =  emf

thus  - dflux / dt =  emf



in principle, it should be do-able because in tracker it also has derivatives of sx sy in the form of vx and vy.

any tips?


Title: Re: can data builder do dflux / dt ?
Post by: Fu-Kwun Hwang on February 25, 2011, 12:03:41 am
I have no ideas about what you really want to do!

Could you provide detail information about the problem itself?


Title: Re: can data builder do dflux / dt ?
Post by: lookang on February 25, 2011, 12:33:40 am
please see my picture in first post on the data builder in Ejs

using the data builder in Ejs, is there a way to type in a model?

currently, i can type in

flux = 4.5*sin(6.281*t)
and emf = - 4.5*6.281*cos(6.281*t)
something like in this YouTube
[youtube]dh3BLyj0oBA[/youtube]
http://www.youtube.com/watch?v=dh3BLyj0oBA time zoom in to 1.06 min
[youtube=dh3BLyj0oBA]

to verify the relationship of d(flux)/dt = - emf

but is it possible to type in say

flux = 4.5*sin(6.281*t)
dfluxdt = d(flux)/dt to get the derivatives?
strangely it seems not documented in the help. maybe it cannot be done yet


Title: Re: can data builder do dflux / dt ?
Post by: Fu-Kwun Hwang on February 25, 2011, 10:09:58 am
Quote
flux = 4.5*sin(6.281*t)
dfluxdt = d(flux)/dt
 to get the derivatives?

The above is symbolic calculation. EJS or java did not have such function yet. May be there are some java library available.

If you already flux = 4.5*sin(6.281*t).
This is a mathematic equation.

Then you can dfluxdt=4.5*6.281*cos(6.281*t) to get the derivate.
It is just calculation. I do not see any modeling activity above.

However,
if you define flux as variable and calculate it's value in your EJS model. You can calculate d(flux)/dt in EJS and compared it with theorical formula with data tool. It is modeling activity.



Title: Re: can data builder do dflux / dt ?
Post by: lookang on February 25, 2011, 10:31:18 am
Oic.
Modeling occur to get flux =?
slowing
Learner try their model
Maybe they think
Flux = sin(t)
Then they see their model eqn is not like the simulated flux.
So they think
Oh maybe flux = sin( w*t) = sin (6.281*t)
Then they compare , still not quite right
They think and try getting closer to simulated flux
Until flux = 4.5*sin(6.281*t)
Then the eqn they hypothesize is same or close enough

And they move on to find emf =?

After different runs and more data collected

The trend of d(flux)/dt = - emf emerged from sufficient evidence.

That is my thinking on modeling. It is quite good to become like scientist is this way of inquiry and discovery
:)

Thanks for your tips!


Title: Re: can data builder do dflux / dt ?
Post by: Fu-Kwun Hwang on February 25, 2011, 02:22:30 pm
Do not provide the answer to the students righy away.
Instead, let's provide help to show visual display of student's thinking.

Flux can be generate with numerical calculation. Then student need to think what kind of mathematics function is related to the flux.
If student think about sin-wave, we generate a sin-wave in the simulation.
... etc. 

Yes. I think you get the ideas. :D


Title: Re: can data builder do dflux / dt ?
Post by: Fu-Kwun Hwang on February 27, 2011, 11:04:52 am
You might want to check out Why the stream of water is narrower at the bottom? (http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=2120.0) as an example of modeling activity.