"P.S. Your reply was very helpful (exactly what I was looking for)
You must be a teacher (info that I needed on the level I needed it)!!"

Lol, thanks, I actually just have a very good teacher (I'm doing 'A'-Level Applied Maths).

As for the friction, the equation is F=uR. Where 'F' stands for force opposing motion and 'R' is the reaction force between the ball and the object generating the friction, 'u' is the coefficient of friction between the ball and friction generating object (eg, air).
Now we throw F=ma (Newtons 2nd law) Force = Mass x Acceleration.
If we equate these we get ma=uR. This shows that the deceleration of the ball due to air resistance is a=uR/m, and that is as far as I can take you being as we haven't yet covered air resistance in maths yet :(. Sorry.

Actually, there is a more complicated method of doing impacts off walls. It is roughly the same as what I said before but it decreases the rebounding speed.

e = Speed Of Rebound / Speed Of Approach. Where 'e' is the coefficient of restitution between the ball and the wall. You can work out the speed of rebound by:
Speed Of Rebound = e * Speed Of Approach.

You will need to experiment with values for 'e', a value of 0.5 would halve the rebounding speed of the ball, 3/4 would reduce it by 25%. So, if we take e to be 0.5 and the approach speed to be 6m/s, then -
V = e * U (V = resultant velocity, U = initial velocity)
V = 0.5 * 6 => V = 3m/s <----- and this is your new ball speed.

After all this I might actually try writing a dodge ball game myself lol.

Degra