Originally Posted by

**AluminX**
ball._y =(ball._y)+(vy * t) + (0.5*g*t*t);

ball._x= (ball._x)+vx*t;

where g=9.8 and t is an interval of time starting with 1 and incremeting by 0.2

You've almost got it, the only problem is that in the formulas you're using,

d = v0(t) + (1/2)(a)(t^2)

d = vt

'd' is absolute, not relative. You're adding each 'd' (ball._y/x) to the previous one, so just take away the ball._y and ball._x that you are adding in there.

Here's a little experiment i did to make sure what i'm telling you is true:

Code:

var v0 = -100; //initial y velocity
var vx = 20; //constant x velocity
var a = 9.8;
var t = 0;
this.onEnterFrame = function () {
t+=0.2;
ball._y = Stage.height + v0*t + 0.5*a*t*t; //Stage.height makes it start at bottom instead of at top (0)
ball._x = vx*t;
}

Your first example, with the vx and vy, is correct if you want to convert a velocity into its x and y components, but changing the angle every frame would probably be just plain weird

btw, I'm taking Physics right now as well.

~MD