Hi there

I have 2 physic oblects... lets say 2 rectangles...in one state thery should be solid... in another state they should be able to pass each other...

1st state: [1] -> <- [2] = [1][1]
2nd state: [1] -> <- [2] = <- [2][1] ->

Any idea who to make this?

you should use collision filters

Any examples?

Have a look at this thread. It's deals with letting objects pass through each other.
https://developer.anscamobile.com/forum/2011/11/02/collision-detection-not-very-good

I guess you could have a function that says:

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 if "rectangle1" collides with "rectangle2" then 
   if collision.phase == "began" then
       rectangle1:removePhysicsBody()
   elseif collision.phase == "ended" then
       rectangle2:addPhysicsBody()
    end
end