Accelaration physics in ActionScript (Flash MX Game Design Demystified)

Hi forum,

I am having problems understand the formula of finding the future x and y position of an object in regards to accelaration.

I have encountered this problem in the book Flash MX Game Design Demystified.

The problem I am having is in regards to a section on Accelaration. I will point out the explanation given in the book and what I do not understand, ok, here it goes: (the following is an excerpt from the book)

[Book excerpt]
If you know the current position and velocity of an object, then you can find its position at any time in the future. You can fidn the future position by using the following equation:

xposition_future = xposition_now + xspeed_nowtime + 1/2(xaccelaration)*time^2


yposition_future = yposition_now + yspeed_nowtime + 1/2(yaccelaration)*time^2
[/Book excerpt]

While I understand the first part of both equations, that is, taking the current x position of an object and adding the speed times time of that object. So if you had a dot at (5, 0) and it was moving at 3 points per frame (using Flash frames as the measurement of time), then the future position of it in say 5 frames would be 5 + 3*5 = 20. This part I understand.

However the second part of the equation, which states ‘1/2*(yaccelaration)*time^2’. I do not have a grasp on.

I would greatly appreciate help from anyone who can explain this formula with a practical example.

Thank you for your help in advance