I agree. I'm not interested in a frame by frame animation, because it wouldn't simulate the reality of a pendulum. I do want to avoid the trig but I'm not sure I see how I'd "weigh" the forces of gravity at different angles...hope I can figure it out. Phil
On Tuesday, April 15, 2003, at 07:02 PM, Alan Kay wrote:
What's the model behind the "movin' pictures"?
The simple frame by frame animation has a very weak and almost nonexistent model.
But, as you've seen from our demos and the DVD documentary, even 5th graders can figure out the two line script that represents an excellent 2nd order differential equation of the (almost) constant accelleration of gravity near the surface of the earth. This is what drives a real pendulum.
Now you just have to "see" how the downwards and sideways forces change with the position of the pendulum and you can easily make a real model of it.
Enclosed is a project that has noticed that the rotational force is proportional to the sine of the angle of the pendulum. But, there is a nice way to bypass trig completely by directly "weighing" the forces exerted by gravity at different angles ... heh heh ...
Cheers,
Alan
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At 3:23 PM -0400 4/15/03, Brucestro@aol.com wrote:
Andreas/Phil,
Wouldn't another possilble approach be to create a series of pictures showing all the possible positions of the pendulum and then control it as one would control a cartoon/movie?? (Phil - There are examples of this technique at squeakland.org under the eToys link.)? Another option that comes to mind is to stack each of these pictures on top of each other and move them front to back as required.? Andreas, I'm new to Squeak -- would these ideas work, or am I on the wrong track?
Thanks, Bruce Strothenke Teachers College Columbia University
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