Why does the ball get faster?

1

I have a function that creates a ball and assigns enter frame vent listener. Once the ball
reaches the bottom, it calls the function to create the ball. However the ball goes tthe stage faster. I’m not sure why . Shouldn’t the speed be the same?


package  
{
    import flash.display.MovieClip;
    import flash.events.Event;
    
    /**
     * ...
     * @author 
     */
    public class Document extends MovieClip
    {
        private var ball:Ball;
        
        public function Document() 
        {
            init();
        }
        
        private function init():void {
            createCircle(); 
        }
        
        private function createCircle():void {
            ball = new Ball(); 
            addChild(ball);
            ball.x = Math.random() * stage.stageWidth;
            ball.vy = 0;
            
            ball.addEventListener(Event.ENTER_FRAME, moveBall); 
        }
        
        private function moveBall(event:Event):void {
            ball.y ++
            trace(ball.y);
        
            if (ball.y > stage.stageHeight) {
                ball.y = 0;
                createCircle();
                
            }
        }
        
    }
    
}