I don't get what I'm doing wrong here. It seems like a simple equation. Given time t, starting y0, ending y1, and gravity g, find the initial y velocity vy0 such that y1 is the apex (vy should be 0 at this point in time).

Starting with basic movement equation:

y = y0 + (vy0 * t) + (0.5 * g * t?)

--> (vy0 * t) = y - y0 - (0.5 * gt?)

--> vy0 = [ (y - y0 - (0.5 * gt?) ] / t

I then set the bullet behavior angle to 270 degrees, and the speed to the absolute value of vy0, and the gravity to g. But it travels way past the point which I had intended to be the apex of the curve.

Here is the code:

<img src="http://dl.dropbox.com/u/12667027/Construct%202/Ballistics/ballistics.png" border="0">

Here is the capx:

What am I missing?

-- cacotigon