performance issue on iphone

hi, i am making an iphone game.i have a drum with 49 lottery balls bouncing off each other and a spinner to spin the thing. it runs fine on the simulator, but it gets really chopping even running on the iphone 4. how can i improve it? do i have to make the 3d model with less polygones?? i have a collider attached to all the balls and drums with lightings

Check out this official Unity page about performance tuning for iOS:

There is also a nice article in Unity Creative Jan/Feb 2011