Physics bodys

Hi
i have a draggable block, one ground and one ball, all objects have physics, but i want to apply my physics only on the ball with ground and draggable block, not on the ground with the draggable object.
some like, the ground and draggable object have physics, but dont interact, only the ball can interact with ground and draggable block.
how can I restrict my interactions of objects?

Thanks [import]uid: 26056 topic_id: 20779 reply_id: 320779[/import]