[sugar] [OLPC-Games] Physics -- Newtonian mechanics.. for kids!

[Brian Jordan]

Hi Yoshiki,

These are great! I've added them to
http://wiki.laptop.org/go/Physics_(activity) .  Feel free to add more
yourself via the upload mechanism:
http://wiki.laptop.org/go/Special:Upload ! A priority is XML-format
scene saving, so we can share great scenes like yours and those that
will be made in the future. Physics is not "ready for deployment"
until scenes can be saved and shared.

[...]
>> >> So we could simulate a pendulum or a Newton's cradle? How do you
>> >> handle collisions?
>> >
>> >  A pendulum for sure, but my version of three pendulums putting
>> > together doesn't show the expected behavior.  The elasticity isn't
>> > right for it, it seems.

Yoshiki, Edward -- Physics is currently contstrained by capabilities
of the open source Box2D physics library. Any added engine
capabilities should be added upstream to their project. See
http://www.box2d.org , and there is a thriving development community
(and the project founder/main coder responds to forum questions)
http://www.box2d.org/forum/

Box2D Manual - http://www.box2d.org/manual.html - covers (most of) the
capabilities of Box2D
Erin Catto's Box2D GDC 2005, 2006, 2007, 2008 slides:
http://www.gphysics.com/downloads

For visualizing concrete possibilities (i.e., easy-to-access projects
using Box2D or ports of Box2D):
http://box2dflash.sourceforge.net/ - Actionscript 3 Box2D
    I tried this on the XO with the latest joyride in gnash... it
wouldn't load. Will somebody please try with Flash?
http://jbox2d.org/ - Java box2d... made by my brother :) No chance of
working on the XO any time soon.
http://box2d-js.sourceforge.net/index2.html - Javascript Box2D -
actually has the 5-ball pendulum you describe, in addition to a cool
motorjoint-based ball-paddling/juggling device
     I tested JS on the XO with the latest joyride -- it ran
reasonably with two objects, unreasonably slow with three.

I will be adding contextual menus (time-based... see Paint for an
example) to the tool selections so you can change friction, elasticity
(Box2D: restitution), mass (Box2D: density), color, etc of each
element before (and maybe eventually after) adding. These are all
supported in Box2D.

>>
>> What does it do? Can you get it to tell you what values of momentum
>> and energy are passed through from balls 1-->2-->3?
>

See again the Box2D manual, MANY things are possible. I think,
interestingly, once we add diagnostic information (visual--using
colors and force-lines, auditory--using force-variable volume sound
effects, and graph-able data graphing or storage) to Physics, many
more opportunities for self directed learning arise. I appreciate very
much any ideas (or code) that solves the difficult challenge of
displaying and letting kids play with this data they are generating
just by their use of Box2D.

I am glad others understand the implications this amazing open source
engine will have on learning Physics. :)
http://wiki.laptop.org/go/Physics_meetings/July_10%2C_2008
     We had a (disorganized, last-minute) meeting yesterday to discuss
next steps for the OLPC Physics community. We are looking into making
movement drawing faster on the XO (as it seems, surprisingly, to be
our limiting Physics performance factor), a common format between our
collective physics playgrounds, and involving developers of other
(many closed source) physics engines to consider helping us and, in
some cases, Box2D.
http://wiki.laptop.org/go/User:Bjordan/Ideas/Teacher_involvement#Physics

Cheers,
Brian

Ahh, the importance of having a working demo... :)

>  Heh, of course you can try by yourself.  But if you put a circle on
> the floor (stand still), and make another hit from the side, the
> momentum is shared by these two circles and both of them move together
> at the same speed.
>
>> Have you tried two pendula hanging from a horizontal string? Do you
>> get the expected transfer of energy back and forth?
>
>  Yes, but no.  I'm not sure what you mean by a horizontal string, but
> the string I made is not flexible enough to make it happen.
>
>  Speaking of examples, the screenshots at
> http://wiki.laptop.org/go/Physics_(activity) aren't exactly something
> I found "physics-y"; these are more like story telling in picture
> books.  I made some examples (two pendula and a mesh, I did an arch
> but it is gone).  These might catch more attention from teachers and
> educators.
>
> -- Yoshiki
>
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