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

Yoshiki Ohshima yoshiki
Tue Jul 15 19:09:03 EDT 2008

```> >  Heh, of course you can try by yourself.
>
> I want to know what happens in your code. Can you send it to me?

There is no code, and I don't know how to send anything.  I just
played around it on XO, and took photos but it couldn't same data into
Journal.

> > 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.
>
> That's unphysical, and I would only program that way in a fantasy
> setting. In a head-on elastic collision of two circles of equal mass,
> the hitter should stop dead, transferring all of its energy and
> momentum to the one it hit. As any pool payer knows for the case of
> spheres. In a Newton's cradle the momentum and energy passes from ball
> to ball at the speed of sound in the material of the balls.

If the ball is made of silly putty, something like this can happen,
and as others pointed out (and in my second email mentions it), it is
just wrong elasticity given to the circles.

> >> 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.
>
> Tie a string between two points at the same height.
>
> Then tie a pendulum to the string.
>
> Then tie another pendulum of the same length and mass to a different
> point on the string.
>
>    \____/
>     |       |
>    o      o
>
> Start one pendulum in the direction perpendicular to the plane of the
> diagram. It will gradually transfer energy and momentum to the other
> almost completely, and then start up again while the other slows down
> and stops, and so on.

Edward... I know what it is.  I'm just saying that there is no
"string", it isn't trivial to make the same length or size of
something more than one, nor there is no perpendicular plane in
"Physics" (yet).

-- Yoshiki

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