To move the blue or green sphere around, click and drag. The red sphere is the center of mass and will update itself automatically.<br /><br />

To give it a push, hold down `shift` while clicking and dragging. You'll see an arrow that shows the push you're about to give. (First click the point where you want to apply the push, then drag backwards to create the magnitude and direction of the push.)<br /><br />

You can also change the sizes of the spheres:
<ul>
<li>a: make blue sphere bigger</li>
<li>s: make blue sphere smaller</li>
<li>k: make green sphere bigger</li>
<li>l: make green sphere smaller</li>
</ul>


Press 'r' to reset.

<div id="glowscript" class="glowscript">
<link type="text/css" href="http://www.glowscript.org/css/redmond/1.1/jquery-ui.custom.css" rel="stylesheet" />
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<script type="text/javascript" src="http://www.glowscript.org/package/RSrun.1.1.min.js"></script>
<script type="text/javascript">
;(function() {
var __g=typeof global!=='undefined'?global:window;__g=(__g.__streamline||(__g.__streamline={}));__g.setEF=__g.setEF||function(e,f){e.__frame = e.__frame||f};var __srcName='undefined_.js';
function __func(_,__this,__arguments,fn,index,frame,body){if(!_){return __future.call(__this,fn,__arguments,index)}frame.file=__srcName;frame.prev=__g.frame;__g.frame=frame;try{body()}catch(e){__g.setEF(e,frame.prev);__propagate(_,e)}finally{__g.frame=frame.prev}}
function __cb(_,frame,offset,col,fn){frame.offset=offset;frame.col=col;var ctx=__g.context;return function ___(err,result){var oldFrame=__g.frame;__g.frame=frame;__g.context=ctx;try{if(err){__g.setEF(err,frame);return _(err)}return fn(null,result)}catch(ex){__g.setEF(ex,frame);return __propagate(_,ex)}finally{__g.frame=oldFrame}}}
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function __trap(err){if(err){if(__g.context&&__g.context.errorHandler)__g.context.errorHandler(err);else console.error("UNCAUGHT EXCEPTION: "+err.message+"\n"+err.stack)}}
/*     1 */ function main(wait) {
              var version, box, sphere, cylinder, pyramid, cone, helix, ellipsoid, ring, arrow, display, vector, _$GS_$END, scene, _$rapyd$_Temp, _$rapyd$_print, arange, radjump, tolerance, drag, dt, left, right, tube, com, impulse, left_trail, right_trail, com_trail;
/*    36 */   function reset() {
/*    38 */     left.radius = 0.4;
/*    40 */     left.pos = vec(2["-u"](), 0, 0);
/*    42 */     left.vol = 4["/"](3)["*"](pi)["*"](Math.pow(left.radius, 3));
/*    44 */     left.v = vec(0, 0, 0);
/*    46 */     right.radius = 0.3;
/*    48 */     right.pos = vec(2, 0, 0);
/*    50 */     right.vol = 4["/"](3)["*"](pi)["*"](Math.pow(right.radius, 3));
/*    52 */     right.v = vec(0, 0, 0);
/*    54 */     tube.pos = vec(2["-u"](), 0, 0);
/*    56 */     tube.axis = vec(1, 0, 0);
/*    58 */     tube.size = vec(4, 0.1, 0.1);
/*    60 */     tube.vol = pi["*"](Math.pow(tube.size.y, 2))["*"](tube.size.x);
/*    62 */     com.pos = left.pos["*"](left.vol)["+"](right.pos["*"](right.vol))["+"](tube.pos["+"](norm(tube.axis)["*"](tube.size.x)["*"](0.5))["*"](tube.vol))["/"](left.vol["+"](right.vol)["+"](tube.vol));
/*    64 */     left.v = 0;
/*    66 */     right.v = 0;
/*    68 */     left.omega = 0;
/*    70 */     right.omega = 0;
              };
/*    73 */   function update() {
/*    75 */     left.vol = 4["/"](3)["*"](pi)["*"](Math.pow(left.radius, 3));
/*    77 */     right.vol = 4["/"](3)["*"](pi)["*"](Math.pow(right.radius, 3));
/*    79 */     tube.pos = left.pos;
/*    81 */     tube.axis = norm(right.pos["-"](left.pos));
/*    83 */     tube.size.x = mag(right.pos["-"](left.pos));
/*    85 */     tube.vol = pi["*"](Math.pow(tube.size.y, 2))["*"](tube.size.x);
/*    87 */     com.pos = left.pos["*"](left.vol)["+"](right.pos["*"](right.vol))["+"](tube.pos["+"](norm(tube.axis)["*"](tube.size.x)["*"](0.5))["*"](tube.vol))["/"](left.vol["+"](right.vol)["+"](tube.vol));
              };
/*    90 */   function killtrails() {
/*    93 */     left_trail.stop();
/*    95 */     left_trail.clear();
/*    97 */     right_trail.stop();
/*    99 */     right_trail.clear();
/*   101 */     com_trail.stop();
/*   103 */     com_trail.clear();
              };
/*   106 */   function key(event) {
/*   107 */     var trails;
/*   109 */     if ((event.which === 65)) {
/*   111 */       left.radius += radjump;
                }
/*   113 */      else if ((event.which === 83)) {
/*   115 */       left.radius -= radjump;
                }
/*   117 */      else if ((event.which === 75)) {
/*   119 */       right.radius += radjump;
                }
/*   121 */      else if ((event.which === 76)) {
/*   123 */       right.radius -= radjump;
                }
/*   125 */      else if ((event.which === 82)) {
/*   127 */       reset();
/*   129 */       killtrails();
                }
/*   131 */      else if ((event.which === 84)) {
/*   133 */       trails *= 1["-u"]();
                }
                
                
                
                
                
              ;
/*   136 */     update();
              };
/*   139 */   function down() {
/*   141 */     if (scene.mouse.shift) {
/*   143 */       impulse.visible = true;
/*   145 */       impulse.pos = scene.mouse.pos;
/*   147 */       impulse.axis = vec(0, 0, 0);
/*   149 */       impulse.end = impulse.pos;
                }
/*   151 */      else {
/*   153 */       if ((mag(scene.mouse.pos["-"](left.pos)) < tolerance)) {
/*   155 */         left.drag = true;
                  }
                ;
/*   158 */       if ((mag(scene.mouse.pos["-"](right.pos)) < tolerance)) {
/*   160 */         right.drag = true;
                  }
                ;
                }
              ;
              };
/*   165 */   function move() {
/*   167 */     if (left.drag) {
/*   169 */       left.pos = scene.mouse.pos;
/*   171 */       update();
                }
              ;
/*   174 */     if (right.drag) {
/*   176 */       right.pos = scene.mouse.pos;
/*   178 */       update();
                }
              ;
/*   181 */     if (scene.mouse.shift) {
/*   183 */       impulse.pos = scene.mouse.pos;
/*   185 */       impulse.axis = impulse.end["-"](impulse.pos);
                }
              ;
              };
/*   189 */   function up(wait) {
                var v, omega;
                var __frame = {
                  name: "up",
                  line: 189
                };
                return __func(wait, this, arguments, up, 0, __frame, function __$up() {
/*   193 */       left.drag = false;
/*   195 */       right.drag = false;
/*   197 */       impulse.visible = false;
                  return (function __$up(__then) {
/*   199 */         if (scene.mouse.shift) {
/*   201 */           v = impulse.axis["/"](left.vol["+"](right.vol)["+"](tube.vol));
/*   203 */           omega = cross(impulse.end["-"](com.pos), impulse.axis)["/"](left.vol["*"](Math.pow(mag(left.pos["-"](com.pos)), 2))["+"](right.vol["*"](Math.pow(mag(right.pos["-"](com.pos)), 2)))["+"](tube.vol["*"](Math.pow(mag(tube.pos["-"](com.pos)), 2))["/"](3)));
/*   205 */           left.v = v;
/*   207 */           right.v = v;
/*   209 */           left.omega = omega;
/*   211 */           right.omega = omega;
/*   213 */           left_trail.start();
/*   215 */           right_trail.start();
/*   217 */           com_trail.start();
                      return (function ___(__break) {
                        var __more;
                        var __loop = __cb(wait, __frame, 0, 0, function __$up() {
                          __more = false;
/*   219 */               var __1 = true;
                          if (__1) {
/*   221 */                 return rate(1["/"](dt), __cb(wait, __frame, 32, -1, function __$up() {
/*   223 */                   left.pos = left.pos["+"](left.v["+"](cross(left.omega, left.pos["-"](com.pos)))["*"](dt));
/*   225 */                   right.pos = right.pos["+"](right.v["+"](cross(right.omega, right.pos["-"](com.pos)))["*"](dt));
/*   227 */                   update();
                              while (__more) {
                                __loop();
                              };
                              __more = true;
                            }));
                          }
                           else {
                            __break();
                          }
                        ;
                        });
                        do {
                          __loop();
                        } while (__more);
                        __more = true;
                      })(function __$up() {
                        __then();
                      });
                    }
                     else {
                      __then();
                    }
                  ;
                  })(function __$up() {
                    wait();
                  });
                });
              };
              var __frame = {
                name: "main",
                line: 1
              };
              return __func(wait, this, arguments, main, 0, __frame, function __$main() {
/*     3 */     version = ["1.1","glowscript",];
/*     4 */     window.__GSlang = "vpython";
/*     5 */     box = vp_box;
/*     6 */     sphere = vp_sphere;
/*     7 */     cylinder = vp_cylinder;
/*     8 */     pyramid = vp_pyramid;
/*     9 */     cone = vp_cone;
/*    10 */     helix = vp_helix;
/*    11 */     ellipsoid = vp_ellipsoid;
/*    12 */     ring = vp_ring;
/*    13 */     arrow = vp_arrow;
/*    14 */     display = canvas;
/*    15 */     vector = vec;
/*    16 */     _$GS_$END = 0;
/*    17 */     scene = canvas();
/*    18 */     _$rapyd$_Temp = 0;
/*    19 */     _$rapyd$_print = print;
/*    20 */     arange = range;
/*    22 */     radjump = 0.01;
/*    24 */     tolerance = 0.2;
/*    26 */     drag = "0";
/*    28 */     dt = 0.001;
/*    30 */     scene.range = 7;
/*    32 */     scene.width = 640;
/*    34 */     scene.height = 800;
/*   232 */     left = sphere({
/*   232 */       color: color.blue
                });
/*   234 */     right = sphere({
/*   234 */       color: color.green
                });
/*   236 */     tube = cylinder({
/*   236 */       size: vec(1, 0.1, 0.1)
                });
/*   238 */     com = sphere({
/*   238 */       radius: 0.1,
/*   238 */       color: color.red
                });
/*   240 */     left.v = vec(0, 0, 0);
/*   242 */     right.v = vec(0, 0, 0);
/*   244 */     impulse = arrow({
/*   244 */       pos: vec(0, 0, 0),
/*   244 */       shaftwidth: 0.2,
/*   244 */       axis: vec(0, 0, 0)
                });
/*   246 */     impulse.visible = false;
/*   248 */     left_trail = attach_trail(left, {
/*   248 */       radius: 0.15["*"](left.radius)
                });
/*   250 */     right_trail = attach_trail(right, {
/*   250 */       radius: 0.15["*"](right.radius)
                });
/*   252 */     com_trail = attach_trail(com);
/*   254 */     left_trail.stop();
/*   256 */     right_trail.stop();
/*   258 */     com_trail.stop();
/*   260 */     reset();
/*   262 */     update();
/*   264 */     scene.bind("keydown", key);
/*   266 */     scene.bind("mousedown", down);
/*   268 */     scene.bind("mousemove", move);
/*   270 */     scene.bind("mouseup", up);
                wait();
              });
            };
/*   272 */ main;

;$(function(){ window.__context = { glowscript_container: $("#glowscript").removeAttr("id") }; main() })})()
</script>
</div>