You can drag a ball from one place to another. You can move or toss a ball a bit outside the circular wall, but it'll come back. Also, you can move a ball so it overlaps another. If you do that, they'll have to separate before they can bounce against each other again. You can toss the ball, too.

If you move your mouse outside the applet, the motion stops until you move it back to the applet.

I'm still working on this one. A bunch of balls bounce off each other and off the spherical wall. There's a slight gravitational field. Perfectly elastic collisions. Actually they're all in a plane, so it's easier figure things out. Maybe I'll try changing it to three dimensions sometime.

Note how after a while, the energy gets transferred to the little balls. They zing around while the big ones loll at the bottom. Note that the mass of a ball is proportional to the cube of its radius since they're supposed to be 3-dimensional.

Parameters:

• color -- the color of the circle the ball move in. Random default. Format for a color is three integers separated by colons. The first is the hue (from 0 to 360), the second is saturation (from 0 to 100) and the third is brightness (from 0 to 100). For instance,

  <param name=color value="0:100:100">

  is bright red.
• nballs -- the number of balls in the sphere. Default 4.
• gravity -- the gravitational constant times 1000. Default 0.
• sound -- whether there are bells sounded or not. Default yes.
• balldata -- an array of data for each ball to be specified. Unspecified balls get randomly set. Format is a list separated by semicolons. For each ball, 5 integers are expected (separated by commas). The first is the radius of the ball, an integer with the unit measurement being 1/1000 of the radius of the circular wall. The second and third are the initial x and y coordinates for the center of the ball, each being an integer with the same unit of measurement (1/1000 of the radius of the circular wall), the 4th and 5th are the initial velocity coordinates (same units). An optional color may be given for the ball. For instance,

  < param name=balldata value=
  "300,0,0,0,0,0:0:100;200,0,500,0,100">

  specifies that the first ball has a radius 300/1000 of that of the circular wall, is centered and has no motion, but will be colored white; the second ball will have a radius of 200/1000, placed above the first, initially move up, and be randomly colored; other balls will be randomly initialized.
• grid -- the size of a grid. If 0 (the default) then no grid is shown; otherwise, how far apart grid lines are shown (sime units)

to the summary. to the cover page. to web references.

David E. Joyce
Department of Mathematics and Computer Science
Clark University
Worcester, MA 01610