// set gravity amount
var gravity:Number = .00098;

// set starting velocity
var dx:Number = .2;
var dy:Number = -.8;

// mark start time and add listener
var lastTime:int = getTimer();
addEventListener(Event.ENTER_FRAME, animateBall);

// step animation
function animateBall(event:Event) {
	
	// get time difference
	var timeDiff:int = getTimer() - lastTime;
	lastTime += timeDiff;
	
	// adjust vertical speed for gravity
	dy += gravity * timeDiff;
		
	// move ball
	ball.x += timeDiff * dx;
	ball.y += timeDiff * dy;
}