Flash / Flex / ActionScript/Animation/Velocity

Calculating position based on velocity

 
package {
  import flash.display.*;
  import flash.events.*;
  import flash.utils.*;
  public class Main extends Sprite {
    private var distancePerSecond:int = 50;  // Pixels to move per second
    private var now:int;                     // The current time
    private var then:int;                    // The last screen-update time
    private var circle:Shape;                // The object to animate
    public function Main(  ) {
      circle = new Shape(  );
      circle.graphics.beginFill(0x0000FF, 1);
      circle.graphics.lineStyle(1);
      circle.graphics.drawEllipse(0, 0, 25, 25);
      addChild(circle);
      then = getTimer(  );
      now  = then;
      addEventListener(Event.ENTER_FRAME, enterFrameListener);
    }
    private function enterFrameListener (e:Event):void {
      then = now;
      now = getTimer(  );
      var elapsed:int = now - then;
      var numSeconds:Number = elapsed / 1000;
      var moveAmount:Number = distancePerSecond * numSeconds;

      circle.x += moveAmount;
    }
  }
}

Change speed direction after hitting the boundary

 
package {
     import flash.display.Sprite;
     import flash.events.Event;
     import flash.geom.ColorTransform;
     import flash.geom.Rectangle;
     
     public class Main extends Sprite {
          public var speedX:int = 10;
          public var speedY:int = -10;
          public function Main() {
               addEventListener(Event.ENTER_FRAME, onEnterFrame);
               graphics.beginFill(0xFF, 1);
               graphics.drawCircle(0, 0, 25);
               graphics.endFill();
               var colorTransform:ColorTransform = new ColorTransform();
               colorTransform.color = Math.random()*0xFFFFFF;
               transform.colorTransform = colorTransform;
          }
          
          private function onEnterFrame(event:Event):void {
               x += speedX;
               y += speedY;
               var bounds:Rectangle = getBounds(parent);
               if (bounds.left < 0 || bounds.right > stage.stageWidth) {
                    speedX *= -1;
               }
               if (bounds.top < 0 || bounds.bottom > stage.stageHeight) {
                    speedY *= -1;
               }
          }
     }
}

Velocity Animation

 
package {
    import flash.display.Sprite;
    import flash.events.Event;
    
    public class Main extends Sprite {
        private var _sprite:Sprite = new Sprite(  );
        
        public function Main(  ) {
            _sprite.graphics.beginFill(0x0000ff, 100);
            _sprite.graphics.drawCircle(0, 0, 25);
            _sprite.graphics.endFill(  );
            _sprite.x = 50;
            _sprite.y = 10;
            addChild(_sprite);
            addEventListener(Event.ENTER_FRAME, onEnterFrame);
        }
        
        public function onEnterFrame(event:Event):void {
        _sprite.x += 1;
        _sprite.y += 2;
        }
    }    
}