The one above is an example of naturally accelerated motion.

We can say the gravity acceleration close to the Earth surface is a=-g con -g=-9,8m/s², while the modulus of acceleration is g=9,8m/s².

Actually the modulus of g can vary considering different values for latitude and longitude.
These variations, anyway, are negligible and the modulus of g is regarded as constant.

In the example '.swf' it was used the formula y-y0=v0t-1/2gt² to make the ball fall. y0 is the initial vertical position of the ball, while v0 is its initial velocity.

Suppose to have the ball start falling at the height h with an initial velocity equals to 0. Then these formulas turn out to be particularly interesting:

√((2h)/g) which represents the falling time and √(2gh) which represents the final velocity.

In our example, having h the same value every time the ball starts falling (after pressing the 'repeat' button) and being the final point always the same, it results in having the same values for falling time and final velocity.