Colision problem

[Speleon]

hi everyone

 

(sorry for my english i am french)

 

i'm making a game where the player controls a ball and must avoid traps like circulars saws. (yeah, original isn't it?).

 

in the first level there is only one saw. I manage colision like this :

 

in the second level there are two saw. I created a group like this :

 

but how can i manage colisions with each element of the group and the ball? i tried many ways but didn't find the right one :/

could you help me please? thank you.