[as3] Gravity

[TehMadHatter]

Alright well, I am trying to learn about gravity and NO I am not going to just leach someones gravity so please don't just give me someone elses...I tried this on my own and it does work...But I don't know if the way I did it will work in the future when I add other things

At the part:

		if (jumpSpeed < 0) {
			jumpSpeed *= -1.3;
			trace(ball.y);
			ball.y += jumpSpeed + 2.7;
		}

I added the +2.7 because it was 2.7 high on the y axis (negative)
But I don't know the reason why

import flash.events.KeyboardEvent;
import flash.events.Event;





//Detect Mouse Location
var mouseLocText:TextField = new TextField();
addEventListener(Event.ENTER_FRAME, showMouseLoc);
function showMouseLoc(X1:Event) {
mouseLocText.text = "X="+mouseX+" Y="+mouseY;
mouseLocText.x = 300;
mouseLocText.y = 300;
addChild(mouseLocText);
}





ball.addEventListener(Event.ENTER_FRAME, animate);
stage.addEventListener(KeyboardEvent.KEY_DOWN, keyPush);
stage.addEventListener(KeyboardEvent.KEY_UP, keyPull);

var leftArrow:Boolean = false;
var rightArrow:Boolean = false;
var spacebar:Boolean = false;
var isJumping:Boolean = false;
var speed:Number = 5;
var jumpSpeed:Number = 0;
var maxjumpSpeed:Number = 15;
var count:Number = 0;
function jump():void
{
	if (!isJumping) {
		isJumping = true;
		jumpSpeed -= maxjumpSpeed;
		ball.y += jumpSpeed;
	}
	if (jumpSpeed < -maxjumpSpeed / 5) {
		jumpSpeed /= 1.3;
		ball.y += jumpSpeed;
	} else {
		if (jumpSpeed < 0) {
			jumpSpeed *= -1.3;
			trace(ball.y);
			ball.y += jumpSpeed + 2.7;
		}
		if (jumpSpeed <= maxjumpSpeed) {
			jumpSpeed *= 1.3;
		ball.y += jumpSpeed;
		}
		else {
		jumpSpeed = 0;
		isJumping = false;
		}
	}
}

function animate(event:Event):void
{
	if (leftArrow) {
		ball.x -= speed;
	}
	if (rightArrow) {
		ball.x += speed;
	}
	if (spacebar || isJumping) {
		jump();
	}
}

function keyPush(event:KeyboardEvent):void
{
	if (event.keyCode == 37) {
		leftArrow = true;
	}
	if (event.keyCode == 39) {
		rightArrow = true;
	}
	if (event.keyCode == 32) {
		spacebar = true;
	}
}
function keyPull(event:KeyboardEvent):void
{
	if (event.keyCode == 37) {
		leftArrow = false;
	}
	if (event.keyCode == 39) {
		rightArrow = false;
	}
	if (event.keyCode == 32) {
		spacebar = false;
	}
}